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* prandom: remove unused functionsJason A. Donenfeld2022-10-111-6/+5
| | | | | | | | | | | | With no callers left of prandom_u32() and prandom_bytes(), as well as get_random_int(), remove these deprecated wrappers, in favor of get_random_u32() and get_random_bytes(). Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Yury Norov <yury.norov@gmail.com> Acked-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: clear new batches when bringing new CPUs onlineJason A. Donenfeld2022-10-061-12/+16
| | | | | | | | | The commit that added the new get_random_{u8,u16}() functions neglected to update the code that clears the batches when bringing up a new CPU. It also forgot a few comments and helper defines, so add those in too. Fixes: 585cd5fe9f73 ("random: add 8-bit and 16-bit batches") Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: fix typos in get_random_bytes() commentWilliam Zijl2022-10-011-5/+5
| | | | | | | | Remove extra whitespace and add a missing word to a sentence describing get_random_bytes(). Signed-off-by: William Zijl <postmaster@gusted.xyz> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: schedule jitter credit for next jiffy, not in two jiffiesJason A. Donenfeld2022-10-011-2/+2
| | | | | | | | | | | | | | Counterintuitively, mod_timer(..., jiffies + 1) will cause the timer to fire not in the next jiffy, but in two jiffies. The way to cause the timer to fire in the next jiffy is with mod_timer(..., jiffies). Doing so then lets us bump the upper bound back up again. Fixes: 50ee7529ec45 ("random: try to actively add entropy rather than passively wait for it") Fixes: 829d680e82a9 ("random: cap jitter samples per bit to factor of HZ") Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Sultan Alsawaf <sultan@kerneltoast.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: add 8-bit and 16-bit batchesJason A. Donenfeld2022-09-291-0/+2
| | | | | | | | | | | There are numerous places in the kernel that would be sped up by having smaller batches. Currently those callsites do `get_random_u32() & 0xff` or similar. Since these are pretty spread out, and will require patches to multiple different trees, let's get ahead of the curve and lay the foundation for `get_random_u8()` and `get_random_u16()`, so that it's then possible to start submitting conversion patches leisurely. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: use init_utsname() instead of utsname()Jason A. Donenfeld2022-09-291-1/+1
| | | | | | | | | | | Rather than going through the current-> indirection for utsname, at this point in boot, init_utsname()==utsname(), so just use it directly that way. Additionally, init_utsname() appears to be available nearly always, so move it into random_init_early(). Suggested-by: Kees Cook <keescook@chromium.org> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: split initialization into early step and later stepJason A. Donenfeld2022-09-291-20/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The full RNG initialization relies on some timestamps, made possible with initialization functions like time_init() and timekeeping_init(). However, these are only available rather late in initialization. Meanwhile, other things, such as memory allocator functions, make use of the RNG much earlier. So split RNG initialization into two phases. We can provide arch randomness very early on, and then later, after timekeeping and such are available, initialize the rest. This ensures that, for example, slabs are properly randomized if RDRAND is available. Without this, CONFIG_SLAB_FREELIST_RANDOM=y loses a degree of its security, because its random seed is potentially deterministic, since it hasn't yet incorporated RDRAND. It also makes it possible to use a better seed in kfence, which currently relies on only the cycle counter. Another positive consequence is that on systems with RDRAND, running with CONFIG_WARN_ALL_UNSEEDED_RANDOM=y results in no warnings at all. One subtle side effect of this change is that on systems with no RDRAND, RDTSC is now only queried by random_init() once, committing the moment of the function call, instead of multiple times as before. This is intentional, as the multiple RDTSCs in a loop before weren't accomplishing very much, with jitter being better provided by try_to_generate_entropy(). Plus, filling blocks with RDTSC is still being done in extract_entropy(), which is necessarily called before random bytes are served anyway. Cc: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: use expired timer rather than wq for mixing fast poolJason A. Donenfeld2022-09-281-7/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Previously, the fast pool was dumped into the main pool periodically in the fast pool's hard IRQ handler. This worked fine and there weren't problems with it, until RT came around. Since RT converts spinlocks into sleeping locks, problems cropped up. Rather than switching to raw spinlocks, the RT developers preferred we make the transformation from originally doing: do_some_stuff() spin_lock() do_some_other_stuff() spin_unlock() to doing: do_some_stuff() queue_work_on(some_other_stuff_worker) This is an ordinary pattern done all over the kernel. However, Sherry noticed a 10% performance regression in qperf TCP over a 40gbps InfiniBand card. Quoting her message: > MT27500 Family [ConnectX-3] cards: > Infiniband device 'mlx4_0' port 1 status: > default gid: fe80:0000:0000:0000:0010:e000:0178:9eb1 > base lid: 0x6 > sm lid: 0x1 > state: 4: ACTIVE > phys state: 5: LinkUp > rate: 40 Gb/sec (4X QDR) > link_layer: InfiniBand > > Cards are configured with IP addresses on private subnet for IPoIB > performance testing. > Regression identified in this bug is in TCP latency in this stack as reported > by qperf tcp_lat metric: > > We have one system listen as a qperf server: > [root@yourQperfServer ~]# qperf > > Have the other system connect to qperf server as a client (in this > case, it’s X7 server with Mellanox card): > [root@yourQperfClient ~]# numactl -m0 -N0 qperf 20.20.20.101 -v -uu -ub --time 60 --wait_server 20 -oo msg_size:4K:1024K:*2 tcp_lat Rather than incur the scheduling latency from queue_work_on, we can instead switch to running on the next timer tick, on the same core. This also batches things a bit more -- once per jiffy -- which is okay now that mix_interrupt_randomness() can credit multiple bits at once. Reported-by: Sherry Yang <sherry.yang@oracle.com> Tested-by: Paul Webb <paul.x.webb@oracle.com> Cc: Sherry Yang <sherry.yang@oracle.com> Cc: Phillip Goerl <phillip.goerl@oracle.com> Cc: Jack Vogel <jack.vogel@oracle.com> Cc: Nicky Veitch <nicky.veitch@oracle.com> Cc: Colm Harrington <colm.harrington@oracle.com> Cc: Ramanan Govindarajan <ramanan.govindarajan@oracle.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Tejun Heo <tj@kernel.org> Cc: Sultan Alsawaf <sultan@kerneltoast.com> Cc: stable@vger.kernel.org Fixes: 58340f8e952b ("random: defer fast pool mixing to worker") Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: avoid reading two cache lines on irq randomnessJason A. Donenfeld2022-09-281-1/+1
| | | | | | | | | | | | | In order to avoid reading and dirtying two cache lines on every IRQ, move the work_struct to the bottom of the fast_pool struct. add_ interrupt_randomness() always touches .pool and .count, which are currently split, because .mix pushes everything down. Instead, move .mix to the bottom, so that .pool and .count are always in the first cache line, since .mix is only accessed when the pool is full. Fixes: 58340f8e952b ("random: defer fast pool mixing to worker") Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: clamp credited irq bits to maximum mixedJason A. Donenfeld2022-09-231-1/+1
| | | | | | | | | Since the most that's mixed into the pool is sizeof(long)*2, don't credit more than that many bytes of entropy. Fixes: e3e33fc2ea7f ("random: do not use input pool from hard IRQs") Cc: stable@vger.kernel.org Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: throttle hwrng writes if no entropy is creditedJason A. Donenfeld2022-09-231-2/+2
| | | | | | | | | | | | | | | If a hwrng source does not provide an entropy estimate, it currently does not contribute at all to the CRNG. In order to help fix this, in case add_hwgenerator_randomness() is called with the entropy parameter set to zero, go to sleep until one reseed interval has passed. While the hwrng thread currently only runs under conditions where this is non-zero, this change is not harmful and prepares for future updates to the hwrng core. Cc: Herbert Xu <herbert@gondor.apana.org.au> Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: use hwgenerator randomness more frequently at early bootDominik Brodowski2022-09-231-12/+10
| | | | | | | | Mix in randomness from hw-rng sources more frequently during early boot, approximately once for every rng reseed. Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: restore O_NONBLOCK supportJason A. Donenfeld2022-09-231-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | Prior to 5.6, when /dev/random was opened with O_NONBLOCK, it would return -EAGAIN if there was no entropy. When the pools were unified in 5.6, this was lost. The post 5.6 behavior of blocking until the pool is initialized, and ignoring O_NONBLOCK in the process, went unnoticed, with no reports about the regression received for two and a half years. However, eventually this indeed did break somebody's userspace. So we restore the old behavior, by returning -EAGAIN if the pool is not initialized. Unlike the old /dev/random, this can only occur during early boot, after which it never blocks again. In order to make this O_NONBLOCK behavior consistent with other expectations, also respect users reading with preadv2(RWF_NOWAIT) and similar. Fixes: 30c08efec888 ("random: make /dev/random be almost like /dev/urandom") Reported-by: Guozihua <guozihua@huawei.com> Reported-by: Zhongguohua <zhongguohua1@huawei.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Andrew Lutomirski <luto@kernel.org> Cc: stable@vger.kernel.org Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* Merge tag 'char-misc-6.0-rc1' of ↵Linus Torvalds2022-08-041-2/+2
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc Pull char / misc driver updates from Greg KH: "Here is the large set of char and misc and other driver subsystem changes for 6.0-rc1. Highlights include: - large set of IIO driver updates, additions, and cleanups - new habanalabs device support added (loads of register maps much like GPUs have) - soundwire driver updates - phy driver updates - slimbus driver updates - tiny virt driver fixes and updates - misc driver fixes and updates - interconnect driver updates - hwtracing driver updates - fpga driver updates - extcon driver updates - firmware driver updates - counter driver update - mhi driver fixes and updates - binder driver fixes and updates - speakup driver fixes All of these have been in linux-next for a while without any reported problems" * tag 'char-misc-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (634 commits) drivers: lkdtm: fix clang -Wformat warning char: remove VR41XX related char driver misc: Mark MICROCODE_MINOR unused spmi: trace: fix stack-out-of-bound access in SPMI tracing functions dt-bindings: iio: adc: Add compatible for MT8188 iio: light: isl29028: Fix the warning in isl29028_remove() iio: accel: sca3300: Extend the trigger buffer from 16 to 32 bytes iio: fix iio_format_avail_range() printing for none IIO_VAL_INT iio: adc: max1027: unlock on error path in max1027_read_single_value() iio: proximity: sx9324: add empty line in front of bullet list iio: magnetometer: hmc5843: Remove duplicate 'the' iio: magn: yas530: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros iio: magnetometer: ak8974: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros iio: light: veml6030: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros iio: light: vcnl4035: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros iio: light: vcnl4000: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros iio: light: tsl2591: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() iio: light: tsl2583: Use DEFINE_RUNTIME_DEV_PM_OPS and pm_ptr() iio: light: isl29028: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() iio: light: gp2ap002: Switch to DEFINE_RUNTIME_DEV_PM_OPS and pm_ptr() ...
| * pm/sleep: Add PM_USERSPACE_AUTOSLEEP KconfigKalesh Singh2022-07-011-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Systems that initiate frequent suspend/resume from userspace can make the kernel aware by enabling PM_USERSPACE_AUTOSLEEP config. This allows for certain sleep-sensitive code (wireguard/rng) to decide on what preparatory work should be performed (or not) in their pm_notification callbacks. This patch was prompted by the discussion at [1] which attempts to remove CONFIG_ANDROID that currently guards these code paths. [1] https://lore.kernel.org/r/20220629150102.1582425-1-hch@lst.de/ Suggested-by: Jason A. Donenfeld <Jason@zx2c4.com> Acked-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Kalesh Singh <kaleshsingh@google.com> Link: https://lore.kernel.org/r/20220630191230.235306-1-kaleshsingh@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | random: correct spelling of "overwrites"Jason A. Donenfeld2022-07-301-1/+1
| | | | | | | | | | | | | | It was missing an 'r'. Fixes: 186873c549df ("random: use simpler fast key erasure flow on per-cpu keys") Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* | random: handle archrandom with multiple longsJason A. Donenfeld2022-07-251-14/+31
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The archrandom interface was originally designed for x86, which supplies RDRAND/RDSEED for receiving random words into registers, resulting in one function to generate an int and another to generate a long. However, other architectures don't follow this. On arm64, the SMCCC TRNG interface can return between one and three longs. On s390, the CPACF TRNG interface can return arbitrary amounts, with four longs having the same cost as one. On UML, the os_getrandom() interface can return arbitrary amounts. So change the api signature to take a "max_longs" parameter designating the maximum number of longs requested, and then return the number of longs generated. Since callers need to check this return value and loop anyway, each arch implementation does not bother implementing its own loop to try again to fill the maximum number of longs. Additionally, all existing callers pass in a constant max_longs parameter. Taken together, these two things mean that the codegen doesn't really change much for one-word-at-a-time platforms, while performance is greatly improved on platforms such as s390. Acked-by: Heiko Carstens <hca@linux.ibm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Acked-by: Borislav Petkov <bp@suse.de> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* | random: use try_cmpxchg in _credit_init_bitsUros Bizjak2022-07-181-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Use `!try_cmpxchg(ptr, &orig, new)` instead of `cmpxchg(ptr, orig, new) != orig` in _credit_init_bits. This has two benefits: - The x86 cmpxchg instruction returns success in the ZF flag, so this change saves a compare after cmpxchg, as well as a related move instruction in front of cmpxchg. - try_cmpxchg implicitly assigns the *ptr value to &orig when cmpxchg fails, enabling further code simplifications. This patch has no functional change. Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* | random: cap jitter samples per bit to factor of HZJason A. Donenfeld2022-07-161-1/+1
|/ | | | | | | | | | | | | | | | | | | Currently the jitter mechanism will require two timer ticks per iteration, and it requires N iterations per bit. This N is determined with a small measurement, and if it's too big, it won't waste time with jitter entropy because it'd take too long or not have sufficient entropy anyway. With the current max N of 32, there are large timeouts on systems with a small CONFIG_HZ. Rather than set that maximum to 32, instead choose a factor of CONFIG_HZ. In this case, 1/30 seems to yield sane values for different configurations of CONFIG_HZ. Reported-by: Vladimir Murzin <vladimir.murzin@arm.com> Fixes: 78c768e619fb ("random: vary jitter iterations based on cycle counter speed") Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* random: update comment from copy_to_user() -> copy_to_iter()Jason A. Donenfeld2022-06-201-1/+1
| | | | | | | | This comment wasn't updated when we moved from read() to read_iter(), so this patch makes the trivial fix. Fixes: 1b388e7765f2 ("random: convert to using fops->read_iter()") Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: quiet urandom warning ratelimit suppression messageJason A. Donenfeld2022-06-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | random.c ratelimits how much it warns about uninitialized urandom reads using __ratelimit(). When the RNG is finally initialized, it prints the number of missed messages due to ratelimiting. It has been this way since that functionality was introduced back in 2018. Recently, cc1e127bfa95 ("random: remove ratelimiting for in-kernel unseeded randomness") put a bit more stress on the urandom ratelimiting, which teased out a bug in the implementation. Specifically, when under pressure, __ratelimit() will print its own message and reset the count back to 0, making the final message at the end less useful. Secondly, it does so as a pr_warn(), which apparently is undesirable for people's CI. Fortunately, __ratelimit() has the RATELIMIT_MSG_ON_RELEASE flag exactly for this purpose, so we set the flag. Fixes: 4e00b339e264 ("random: rate limit unseeded randomness warnings") Cc: stable@vger.kernel.org Reported-by: Jon Hunter <jonathanh@nvidia.com> Reported-by: Ron Economos <re@w6rz.net> Tested-by: Ron Economos <re@w6rz.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: schedule mix_interrupt_randomness() less oftenJason A. Donenfeld2022-06-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It used to be that mix_interrupt_randomness() would credit 1 bit each time it ran, and so add_interrupt_randomness() would schedule mix() to run every 64 interrupts, a fairly arbitrary number, but nonetheless considered to be a decent enough conservative estimate. Since e3e33fc2ea7f ("random: do not use input pool from hard IRQs"), mix() is now able to credit multiple bits, depending on the number of calls to add(). This was done for reasons separate from this commit, but it has the nice side effect of enabling this patch to schedule mix() less often. Currently the rules are: a) Credit 1 bit for every 64 calls to add(). b) Schedule mix() once a second that add() is called. c) Schedule mix() once every 64 calls to add(). Rules (a) and (c) no longer need to be coupled. It's still important to have _some_ value in (c), so that we don't "over-saturate" the fast pool, but the once per second we get from rule (b) is a plenty enough baseline. So, by increasing the 64 in rule (c) to something larger, we avoid calling queue_work_on() as frequently during irq storms. This commit changes that 64 in rule (c) to be 1024, which means we schedule mix() 16 times less often. And it does *not* need to change the 64 in rule (a). Fixes: 58340f8e952b ("random: defer fast pool mixing to worker") Cc: stable@vger.kernel.org Cc: Dominik Brodowski <linux@dominikbrodowski.net> Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: remove rng_has_arch_random()Jason A. Donenfeld2022-06-101-13/+0
| | | | | | | | | | | | | | With arch randomness being used by every distro and enabled in defconfigs, the distinction between rng_has_arch_random() and rng_is_initialized() is now rather small. In fact, the places where they differ are now places where paranoid users and system builders really don't want arch randomness to be used, in which case we should respect that choice, or places where arch randomness is known to be broken, in which case that choice is all the more important. So this commit just removes the function and its one user. Reviewed-by: Petr Mladek <pmladek@suse.com> # for vsprintf.c Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: do not use jump labels before they are initializedJason A. Donenfeld2022-06-101-1/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Stephen reported that a static key warning splat appears during early boot on systems that credit randomness from device trees that contain an "rng-seed" property, because because setup_machine_fdt() is called before jump_label_init() during setup_arch(): static_key_enable_cpuslocked(): static key '0xffffffe51c6fcfc0' used before call to jump_label_init() WARNING: CPU: 0 PID: 0 at kernel/jump_label.c:166 static_key_enable_cpuslocked+0xb0/0xb8 Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0+ #224 44b43e377bfc84bc99bb5ab885ff694984ee09ff pstate: 600001c9 (nZCv dAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : static_key_enable_cpuslocked+0xb0/0xb8 lr : static_key_enable_cpuslocked+0xb0/0xb8 sp : ffffffe51c393cf0 x29: ffffffe51c393cf0 x28: 000000008185054c x27: 00000000f1042f10 x26: 0000000000000000 x25: 00000000f10302b2 x24: 0000002513200000 x23: 0000002513200000 x22: ffffffe51c1c9000 x21: fffffffdfdc00000 x20: ffffffe51c2f0831 x19: ffffffe51c6fcfc0 x18: 00000000ffff1020 x17: 00000000e1e2ac90 x16: 00000000000000e0 x15: ffffffe51b710708 x14: 0000000000000066 x13: 0000000000000018 x12: 0000000000000000 x11: 0000000000000000 x10: 00000000ffffffff x9 : 0000000000000000 x8 : 0000000000000000 x7 : 61632065726f6665 x6 : 6220646573752027 x5 : ffffffe51c641d25 x4 : ffffffe51c13142c x3 : ffff0a00ffffff05 x2 : 40000000ffffe003 x1 : 00000000000001c0 x0 : 0000000000000065 Call trace: static_key_enable_cpuslocked+0xb0/0xb8 static_key_enable+0x2c/0x40 crng_set_ready+0x24/0x30 execute_in_process_context+0x80/0x90 _credit_init_bits+0x100/0x154 add_bootloader_randomness+0x64/0x78 early_init_dt_scan_chosen+0x140/0x184 early_init_dt_scan_nodes+0x28/0x4c early_init_dt_scan+0x40/0x44 setup_machine_fdt+0x7c/0x120 setup_arch+0x74/0x1d8 start_kernel+0x84/0x44c __primary_switched+0xc0/0xc8 ---[ end trace 0000000000000000 ]--- random: crng init done Machine model: Google Lazor (rev1 - 2) with LTE A trivial fix went in to address this on arm64, 73e2d827a501 ("arm64: Initialize jump labels before setup_machine_fdt()"). I wrote patches as well for arm32 and risc-v. But still patches are needed on xtensa, powerpc, arc, and mips. So that's 7 platforms where things aren't quite right. This sort of points to larger issues that might need a larger solution. Instead, this commit just defers setting the static branch until later in the boot process. random_init() is called after jump_label_init() has been called, and so is always a safe place from which to adjust the static branch. Fixes: f5bda35fba61 ("random: use static branch for crng_ready()") Reported-by: Stephen Boyd <swboyd@chromium.org> Reported-by: Phil Elwell <phil@raspberrypi.com> Tested-by: Phil Elwell <phil@raspberrypi.com> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Russell King <linux@armlinux.org.uk> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: account for arch randomness in bitsJason A. Donenfeld2022-06-101-5/+5
| | | | | | | | | | | Rather than accounting in bytes and multiplying (shifting), we can just account in bits and avoid the shift. The main motivation for this is there are other patches in flux that expand this code a bit, and avoiding the duplication of "* 8" everywhere makes things a bit clearer. Cc: stable@vger.kernel.org Fixes: 12e45a2a6308 ("random: credit architectural init the exact amount") Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: mark bootloader randomness code as __initJason A. Donenfeld2022-06-101-4/+3
| | | | | | | | | | | add_bootloader_randomness() and the variables it touches are only used during __init and not after, so mark these as __init. At the same time, unexport this, since it's only called by other __init code that's built-in. Cc: stable@vger.kernel.org Fixes: 428826f5358c ("fdt: add support for rng-seed") Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: avoid checking crng_ready() twice in random_init()Jason A. Donenfeld2022-06-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | The current flow expands to: if (crng_ready()) ... else if (...) if (!crng_ready()) ... The second crng_ready() call is redundant, but can't so easily be optimized out by the compiler. This commit simplifies that to: if (crng_ready() ... else if (...) ... Fixes: 560181c27b58 ("random: move initialization functions out of hot pages") Cc: stable@vger.kernel.org Cc: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: check for signals after page of pool writesJason A. Donenfeld2022-05-221-4/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | get_random_bytes_user() checks for signals after producing a PAGE_SIZE worth of output, just like /dev/zero does. write_pool() is doing basically the same work (actually, slightly more expensive), and so should stop to check for signals in the same way. Let's also name it write_pool_user() to match get_random_bytes_user(), so this won't be misused in the future. Before this patch, massive writes to /dev/urandom would tie up the process for an extremely long time and make it unterminatable. After, it can be successfully interrupted. The following test program can be used to see this works as intended: #include <unistd.h> #include <fcntl.h> #include <signal.h> #include <stdio.h> static unsigned char x[~0U]; static void handle(int) { } int main(int argc, char *argv[]) { pid_t pid = getpid(), child; int fd; signal(SIGUSR1, handle); if (!(child = fork())) { for (;;) kill(pid, SIGUSR1); } fd = open("/dev/urandom", O_WRONLY); pause(); printf("interrupted after writing %zd bytes\n", write(fd, x, sizeof(x))); close(fd); kill(child, SIGTERM); return 0; } Result before: "interrupted after writing 2147479552 bytes" Result after: "interrupted after writing 4096 bytes" Cc: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: wire up fops->splice_{read,write}_iter()Jens Axboe2022-05-201-0/+4
| | | | | | | | | | | | | | Now that random/urandom is using {read,write}_iter, we can wire it up to using the generic splice handlers. Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops") Signed-off-by: Jens Axboe <axboe@kernel.dk> [Jason: added the splice_write path. Note that sendfile() and such still does not work for read, though it does for write, because of a file type restriction in splice_direct_to_actor(), which I'll address separately.] Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: convert to using fops->write_iter()Jens Axboe2022-05-201-32/+35
| | | | | | | | | | | | | Now that the read side has been converted to fix a regression with splice, convert the write side as well to have some symmetry in the interface used (and help deprecate ->write()). Signed-off-by: Jens Axboe <axboe@kernel.dk> [Jason: cleaned up random_ioctl a bit, require full writes in RNDADDENTROPY since it's crediting entropy, simplify control flow of write_pool(), and incorporate suggestions from Al.] Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: convert to using fops->read_iter()Jens Axboe2022-05-201-36/+29
| | | | | | | | | | | | This is a pre-requisite to wiring up splice() again for the random and urandom drivers. It also allows us to remove the INT_MAX check in getrandom(), because import_single_range() applies capping internally. Signed-off-by: Jens Axboe <axboe@kernel.dk> [Jason: rewrote get_random_bytes_user() to simplify and also incorporate additional suggestions from Al.] Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: unify batched entropy implementationsJason A. Donenfeld2022-05-191-92/+55
| | | | | | | | | | | | | | | | | | | | | | | There are currently two separate batched entropy implementations, for u32 and u64, with nearly identical code, with the goal of avoiding unaligned memory accesses and letting the buffers be used more efficiently. Having to maintain these two functions independently is a bit of a hassle though, considering that they always need to be kept in sync. This commit factors them out into a type-generic macro, so that the expansion produces the same code as before, such that diffing the assembly shows no differences. This will also make it easier in the future to add u16 and u8 batches. This was initially tested using an always_inline function and letting gcc constant fold the type size in, but the code gen was less efficient, and in general it was more verbose and harder to follow. So this patch goes with the boring macro solution, similar to what's already done for the _wait functions in random.h. Cc: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: move randomize_page() into mm where it belongsJason A. Donenfeld2022-05-191-32/+0
| | | | | | | | | | | | | | | | | randomize_page is an mm function. It is documented like one. It contains the history of one. It has the naming convention of one. It looks just like another very similar function in mm, randomize_stack_top(). And it has always been maintained and updated by mm people. There is no need for it to be in random.c. In the "which shape does not look like the other ones" test, pointing to randomize_page() is correct. So move randomize_page() into mm/util.c, right next to the similar randomize_stack_top() function. This commit contains no actual code changes. Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: remove mostly unused async readiness notifierJason A. Donenfeld2022-05-191-48/+0
| | | | | | | | | | | | | | | | | | | The register_random_ready_notifier() notifier is somewhat complicated, and was already recently rewritten to use notifier blocks. It is only used now by one consumer in the kernel, vsprintf.c, for which the async mechanism is really overly complex for what it actually needs. This commit removes register_random_ready_notifier() and unregister_random_ ready_notifier(), because it just adds complication with little utility, and changes vsprintf.c to just check on `!rng_is_initialized() && !rng_has_arch_random()`, which will eventually be true. Performance- wise, that code was already using a static branch, so there's basically no overhead at all to this change. Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Acked-by: Petr Mladek <pmladek@suse.com> # for vsprintf.c Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: remove get_random_bytes_arch() and add rng_has_arch_random()Jason A. Donenfeld2022-05-191-33/+16
| | | | | | | | | | | | | | | | | | | | | | | The RNG incorporates RDRAND into its state at boot and every time it reseeds, so there's no reason for callers to use it directly. The hashing that the RNG does on it is preferable to using the bytes raw. The only current use case of get_random_bytes_arch() is vsprintf's siphash key for pointer hashing, which uses it to initialize the pointer secret earlier than usual if RDRAND is available. In order to replace this narrow use case, just expose whether RDRAND is mixed into the RNG, with a new function called rng_has_arch_random(). With that taken care of, there are no users of get_random_bytes_arch() left, so it can be removed. Later, if trust_cpu gets turned on by default (as most distros are doing), this one use of rng_has_arch_random() can probably go away as well. Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Acked-by: Petr Mladek <pmladek@suse.com> # for vsprintf.c Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: move initialization functions out of hot pagesJason A. Donenfeld2022-05-191-25/+21
| | | | | | | | | | | | | | | | | | | | | | | | | Much of random.c is devoted to initializing the rng and accounting for when a sufficient amount of entropy has been added. In a perfect world, this would all happen during init, and so we could mark these functions as __init. But in reality, this isn't the case: sometimes the rng only finishes initializing some seconds after system init is finished. For this reason, at the moment, a whole host of functions that are only used relatively close to system init and then never again are intermixed with functions that are used in hot code all the time. This creates more cache misses than necessary. In order to pack the hot code closer together, this commit moves the initialization functions that can't be marked as __init into .text.unlikely by way of the __cold attribute. Of particular note is moving credit_init_bits() into a macro wrapper that inlines the crng_ready() static branch check. This avoids a function call to a nop+ret, and most notably prevents extra entropy arithmetic from being computed in mix_interrupt_randomness(). Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: make consistent use of buf and lenJason A. Donenfeld2022-05-191-102/+97
| | | | | | | | | The current code was a mix of "nbytes", "count", "size", "buffer", "in", and so forth. Instead, let's clean this up by naming input parameters "buf" (or "ubuf") and "len", so that you always understand that you're reading this variety of function argument. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: use static branch for crng_ready()Jason A. Donenfeld2022-05-191-4/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | Since crng_ready() is only false briefly during initialization and then forever after becomes true, we don't need to evaluate it after, making it a prime candidate for a static branch. One complication, however, is that it changes state in a particular call to credit_init_bits(), which might be made from atomic context, which means we must kick off a workqueue to change the static key. Further complicating things, credit_init_bits() may be called sufficiently early on in system initialization such that system_wq is NULL. Fortunately, there exists the nice function execute_in_process_context(), which will immediately execute the function if !in_interrupt(), and otherwise defer it to a workqueue. During early init, before workqueues are available, in_interrupt() is always false, because interrupts haven't even been enabled yet, which means the function in that case executes immediately. Later on, after workqueues are available, in_interrupt() might be true, but in that case, the work is queued in system_wq and all goes well. Cc: Theodore Ts'o <tytso@mit.edu> Cc: Sultan Alsawaf <sultan@kerneltoast.com> Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: credit architectural init the exact amountJason A. Donenfeld2022-05-181-6/+6
| | | | | | | | | | | RDRAND and RDSEED can fail sometimes, which is fine. We currently initialize the RNG with 512 bits of RDRAND/RDSEED. We only need 256 bits of those to succeed in order to initialize the RNG. Instead of the current "all or nothing" approach, actually credit these contributions the amount that is actually contributed. Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: handle latent entropy and command line from random_init()Jason A. Donenfeld2022-05-181-7/+10
| | | | | | | | | | | | | | | | | Currently, start_kernel() adds latent entropy and the command line to the entropy bool *after* the RNG has been initialized, deferring when it's actually used by things like stack canaries until the next time the pool is seeded. This surely is not intended. Rather than splitting up which entropy gets added where and when between start_kernel() and random_init(), just do everything in random_init(), which should eliminate these kinds of bugs in the future. While we're at it, rename the awkwardly titled "rand_initialize()" to the more standard "random_init()" nomenclature. Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: use proper jiffies comparison macroJason A. Donenfeld2022-05-181-1/+1
| | | | | | | This expands to exactly the same code that it replaces, but makes things consistent by using the same macro for jiffy comparisons throughout. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: remove ratelimiting for in-kernel unseeded randomnessJason A. Donenfeld2022-05-181-44/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The CONFIG_WARN_ALL_UNSEEDED_RANDOM debug option controls whether the kernel warns about all unseeded randomness or just the first instance. There's some complicated rate limiting and comparison to the previous caller, such that even with CONFIG_WARN_ALL_UNSEEDED_RANDOM enabled, developers still don't see all the messages or even an accurate count of how many were missed. This is the result of basically parallel mechanisms aimed at accomplishing more or less the same thing, added at different points in random.c history, which sort of compete with the first-instance-only limiting we have now. It turns out, however, that nobody cares about the first unseeded randomness instance of in-kernel users. The same first user has been there for ages now, and nobody is doing anything about it. It isn't even clear that anybody _can_ do anything about it. Most places that can do something about it have switched over to using get_random_bytes_wait() or wait_for_random_bytes(), which is the right thing to do, but there is still much code that needs randomness sometimes during init, and as a geeneral rule, if you're not using one of the _wait functions or the readiness notifier callback, you're bound to be doing it wrong just based on that fact alone. So warning about this same first user that can't easily change is simply not an effective mechanism for anything at all. Users can't do anything about it, as the Kconfig text points out -- the problem isn't in userspace code -- and kernel developers don't or more often can't react to it. Instead, show the warning for all instances when CONFIG_WARN_ALL_UNSEEDED_RANDOM is set, so that developers can debug things need be, or if it isn't set, don't show a warning at all. At the same time, CONFIG_WARN_ALL_UNSEEDED_RANDOM now implies setting random.ratelimit_disable=1 on by default, since if you care about one you probably care about the other too. And we can clean up usage around the related urandom_warning ratelimiter as well (whose behavior isn't changing), so that it properly counts missed messages after the 10 message threshold is reached. Cc: Theodore Ts'o <tytso@mit.edu> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: move initialization out of reseeding hot pathJason A. Donenfeld2022-05-181-23/+19
| | | | | | | | | | | | | | | Initialization happens once -- by way of credit_init_bits() -- and then it never happens again. Therefore, it doesn't need to be in crng_reseed(), which is a hot path that is called multiple times. It also doesn't make sense to have there, as initialization activity is better associated with initialization routines. After the prior commit, crng_reseed() now won't be called by multiple concurrent callers, which means that we can safely move the "finialize_init" logic into crng_init_bits() unconditionally. Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: avoid initializing twice in credit raceJason A. Donenfeld2022-05-181-5/+5
| | | | | | | | | | | | | | | Since all changes of crng_init now go through credit_init_bits(), we can fix a long standing race in which two concurrent callers of credit_init_bits() have the new bit count >= some threshold, but are doing so with crng_init as a lower threshold, checked outside of a lock, resulting in crng_reseed() or similar being called twice. In order to fix this, we can use the original cmpxchg value of the bit count, and only change crng_init when the bit count transitions from below a threshold to meeting the threshold. Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: use symbolic constants for crng_init statesJason A. Donenfeld2022-05-181-19/+19
| | | | | | | | | | | | | crng_init represents a state machine, with three states, and various rules for transitions. For the longest time, we've been managing these with "0", "1", and "2", and expecting people to figure it out. To make the code more obvious, replace these with proper enum values representing the transition, and then redocument what each of these states mean. Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Joe Perches <joe@perches.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* siphash: use one source of truth for siphash permutationsJason A. Donenfeld2022-05-181-23/+7
| | | | | | | | | | | | | | | | | | The SipHash family of permutations is currently used in three places: - siphash.c itself, used in the ordinary way it was intended. - random32.c, in a construction from an anonymous contributor. - random.c, as part of its fast_mix function. Each one of these places reinvents the wheel with the same C code, same rotation constants, and same symmetry-breaking constants. This commit tidies things up a bit by placing macros for the permutations and constants into siphash.h, where each of the three .c users can access them. It also leaves a note dissuading more users of them from emerging. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: help compiler out with fast_mix() by using simpler argumentsJason A. Donenfeld2022-05-181-21/+23
| | | | | | | | | | | | Now that fast_mix() has more than one caller, gcc no longer inlines it. That's fine. But it also doesn't handle the compound literal argument we pass it very efficiently, nor does it handle the loop as well as it could. So just expand the code to spell out this function so that it generates the same code as it did before. Performance-wise, this now behaves as it did before the last commit. The difference in actual code size on x86 is 45 bytes, which is less than a cache line. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: do not use input pool from hard IRQsJason A. Donenfeld2022-05-181-15/+36
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Years ago, a separate fast pool was added for interrupts, so that the cost associated with taking the input pool spinlocks and mixing into it would be avoided in places where latency is critical. However, one oversight was that add_input_randomness() and add_disk_randomness() still sometimes are called directly from the interrupt handler, rather than being deferred to a thread. This means that some unlucky interrupts will be caught doing a blake2s_compress() call and potentially spinning on input_pool.lock, which can also be taken by unprivileged users by writing into /dev/urandom. In order to fix this, add_timer_randomness() now checks whether it is being called from a hard IRQ and if so, just mixes into the per-cpu IRQ fast pool using fast_mix(), which is much faster and can be done lock-free. A nice consequence of this, as well, is that it means hard IRQ context FPU support is likely no longer useful. The entropy estimation algorithm used by add_timer_randomness() is also somewhat different than the one used for add_interrupt_randomness(). The former looks at deltas of deltas of deltas, while the latter just waits for 64 interrupts for one bit or for one second since the last bit. In order to bridge these, and since add_interrupt_randomness() runs after an add_timer_randomness() that's called from hard IRQ, we add to the fast pool credit the related amount, and then subtract one to account for add_interrupt_randomness()'s contribution. A downside of this, however, is that the num argument is potentially attacker controlled, which puts a bit more pressure on the fast_mix() sponge to do more than it's really intended to do. As a mitigating factor, the first 96 bits of input aren't attacker controlled (a cycle counter followed by zeros), which means it's essentially two rounds of siphash rather than one, which is somewhat better. It's also not that much different from add_interrupt_randomness()'s use of the irq stack instruction pointer register. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Filipe Manana <fdmanana@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: order timer entropy functions below interrupt functionsJason A. Donenfeld2022-05-161-119/+119
| | | | | | | | There are no code changes here; this is just a reordering of functions, so that in subsequent commits, the timer entropy functions can call into the interrupt ones. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
* random: do not pretend to handle premature next security modelJason A. Donenfeld2022-05-151-118/+68
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Per the thread linked below, "premature next" is not considered to be a realistic threat model, and leads to more serious security problems. "Premature next" is the scenario in which: - Attacker compromises the current state of a fully initialized RNG via some kind of infoleak. - New bits of entropy are added directly to the key used to generate the /dev/urandom stream, without any buffering or pooling. - Attacker then, somehow having read access to /dev/urandom, samples RNG output and brute forces the individual new bits that were added. - Result: the RNG never "recovers" from the initial compromise, a so-called violation of what academics term "post-compromise security". The usual solutions to this involve some form of delaying when entropy gets mixed into the crng. With Fortuna, this involves multiple input buckets. With what the Linux RNG was trying to do prior, this involves entropy estimation. However, by delaying when entropy gets mixed in, it also means that RNG compromises are extremely dangerous during the window of time before the RNG has gathered enough entropy, during which time nonces may become predictable (or repeated), ephemeral keys may not be secret, and so forth. Moreover, it's unclear how realistic "premature next" is from an attack perspective, if these attacks even make sense in practice. Put together -- and discussed in more detail in the thread below -- these constitute grounds for just doing away with the current code that pretends to handle premature next. I say "pretends" because it wasn't doing an especially great job at it either; should we change our mind about this direction, we would probably implement Fortuna to "fix" the "problem", in which case, removing the pretend solution still makes sense. This also reduces the crng reseed period from 5 minutes down to 1 minute. The rationale from the thread might lead us toward reducing that even further in the future (or even eliminating it), but that remains a topic of a future commit. At a high level, this patch changes semantics from: Before: Seed for the first time after 256 "bits" of estimated entropy have been accumulated since the system booted. Thereafter, reseed once every five minutes, but only if 256 new "bits" have been accumulated since the last reseeding. After: Seed for the first time after 256 "bits" of estimated entropy have been accumulated since the system booted. Thereafter, reseed once every minute. Most of this patch is renaming and removing: POOL_MIN_BITS becomes POOL_INIT_BITS, credit_entropy_bits() becomes credit_init_bits(), crng_reseed() loses its "force" parameter since it's now always true, the drain_entropy() function no longer has any use so it's removed, entropy estimation is skipped if we've already init'd, the various notifiers for "low on entropy" are now only active prior to init, and finally, some documentation comments are cleaned up here and there. Link: https://lore.kernel.org/lkml/YmlMGx6+uigkGiZ0@zx2c4.com/ Cc: Theodore Ts'o <tytso@mit.edu> Cc: Nadia Heninger <nadiah@cs.ucsd.edu> Cc: Tom Ristenpart <ristenpart@cornell.edu> Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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