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| author | peterz@infradead.org <peterz@infradead.org> | 2023-09-21 12:45:11 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-09-21 19:22:07 +0200 |
| commit | 43adf844951084c266f172561f84c5f8120dd60b (patch) | |
| tree | 6a506adc83de717d2c4bcaa2b3fdded724bba24f /kernel/futex | |
| parent | 9f6c532f59b20580acf8ede9409c9b8dce6e74e1 (diff) | |
| download | linux-43adf844951084c266f172561f84c5f8120dd60b.tar.gz linux-43adf844951084c266f172561f84c5f8120dd60b.tar.bz2 linux-43adf844951084c266f172561f84c5f8120dd60b.zip | |
futex: FLAGS_STRICT
The current semantics for futex_wake() are a bit loose, specifically
asking for 0 futexes to be woken actually gets you 1.
Adding a !nr check to sys_futex_wake() makes that it would return 0
for unaligned futex words, because that check comes in the shared
futex_wake() function. Adding the !nr check there, would affect the
legacy sys_futex() semantics.
Hence frob a flag :-(
Suggested-by: André Almeida <andrealmeid@igalia.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230921105248.048643656@noisy.programming.kicks-ass.net
Diffstat (limited to 'kernel/futex')
| -rw-r--r-- | kernel/futex/futex.h | 21 | ||||
| -rw-r--r-- | kernel/futex/syscalls.c | 2 | ||||
| -rw-r--r-- | kernel/futex/waitwake.c | 3 |
3 files changed, 15 insertions, 11 deletions
diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h index a3f1fceafcbe..0e7821a944a2 100644 --- a/kernel/futex/futex.h +++ b/kernel/futex/futex.h @@ -17,25 +17,26 @@ * Futex flags used to encode options to functions and preserve them across * restarts. */ -#define FLAGS_SIZE_8 0x00 -#define FLAGS_SIZE_16 0x01 -#define FLAGS_SIZE_32 0x02 -#define FLAGS_SIZE_64 0x03 +#define FLAGS_SIZE_8 0x0000 +#define FLAGS_SIZE_16 0x0001 +#define FLAGS_SIZE_32 0x0002 +#define FLAGS_SIZE_64 0x0003 -#define FLAGS_SIZE_MASK 0x03 +#define FLAGS_SIZE_MASK 0x0003 #ifdef CONFIG_MMU -# define FLAGS_SHARED 0x10 +# define FLAGS_SHARED 0x0010 #else /* * NOMMU does not have per process address space. Let the compiler optimize * code away. */ -# define FLAGS_SHARED 0x00 +# define FLAGS_SHARED 0x0000 #endif -#define FLAGS_CLOCKRT 0x20 -#define FLAGS_HAS_TIMEOUT 0x40 -#define FLAGS_NUMA 0x80 +#define FLAGS_CLOCKRT 0x0020 +#define FLAGS_HAS_TIMEOUT 0x0040 +#define FLAGS_NUMA 0x0080 +#define FLAGS_STRICT 0x0100 /* FUTEX_ to FLAGS_ */ static inline unsigned int futex_to_flags(unsigned int op) diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c index 7049a52ef68e..47398926765e 100644 --- a/kernel/futex/syscalls.c +++ b/kernel/futex/syscalls.c @@ -333,7 +333,7 @@ SYSCALL_DEFINE4(futex_wake, if (!futex_validate_input(flags, mask)) return -EINVAL; - return futex_wake(uaddr, flags, nr, mask); + return futex_wake(uaddr, FLAGS_STRICT | flags, nr, mask); } #ifdef CONFIG_COMPAT diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c index fa9757766103..ceb05b876597 100644 --- a/kernel/futex/waitwake.c +++ b/kernel/futex/waitwake.c @@ -155,6 +155,9 @@ int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset) if (unlikely(ret != 0)) return ret; + if ((flags & FLAGS_STRICT) && !nr_wake) + return 0; + hb = futex_hash(&key); /* Make sure we really have tasks to wakeup */ |