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| author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2017-04-17 10:32:01 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-04-17 12:35:33 +0200 |
| commit | 197decefdb79d6f1350ba0316ce26ba737372d0c (patch) | |
| tree | 79d32c8ebc3515cf7de726694105b3aa0d203ca1 | |
| parent | e69176d68d26d63d9214797c191ce65358ea1ecf (diff) | |
| download | linux-197decefdb79d6f1350ba0316ce26ba737372d0c.tar.gz linux-197decefdb79d6f1350ba0316ce26ba737372d0c.tar.bz2 linux-197decefdb79d6f1350ba0316ce26ba737372d0c.zip | |
efi/libstub/arm: Don't use TASK_SIZE when randomizing the RT space
As reported by James, Catalin and Mark, commit:
e69176d68d26 ("ef/libstub/arm/arm64: Randomize the base of the UEFI rt services region")
... results in a crash in the firmware, regardless of whether KASLR
is in effect or not and whether the firmware implements EFI_RNG_PROTOCOL
or not.
Mark has identified the root cause to be the inappropriate use of
TASK_SIZE in the stub, which arm64 defines as:
#define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \
TASK_SIZE_32 : TASK_SIZE_64)
and testing thread flags at this point results in the dereference of
pointers in uninitialized structures.
So instead, introduce a preprocessor symbol EFI_RT_VIRTUAL_LIMIT and
define it to TASK_SIZE_64 on arm64 and TASK_SIZE on ARM, both of which
are compile time constants. Also, change the 'headroom' variable to
static const to force an error if this might change in the future.
Tested-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: James Morse <james.morse@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20170417093201.10181-2-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | drivers/firmware/efi/libstub/arm-stub.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c index 1e45ec51b094..8181ac179d14 100644 --- a/drivers/firmware/efi/libstub/arm-stub.c +++ b/drivers/firmware/efi/libstub/arm-stub.c @@ -32,6 +32,12 @@ #define EFI_RT_VIRTUAL_BASE SZ_512M #define EFI_RT_VIRTUAL_SIZE SZ_512M +#ifdef CONFIG_ARM64 +# define EFI_RT_VIRTUAL_LIMIT TASK_SIZE_64 +#else +# define EFI_RT_VIRTUAL_LIMIT TASK_SIZE +#endif + static u64 virtmap_base = EFI_RT_VIRTUAL_BASE; efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg, @@ -236,8 +242,9 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, * shift of 21 bit positions into account when scaling * the headroom value using a 32-bit random value. */ - u64 headroom = TASK_SIZE - EFI_RT_VIRTUAL_BASE - - EFI_RT_VIRTUAL_SIZE; + static const u64 headroom = EFI_RT_VIRTUAL_LIMIT - + EFI_RT_VIRTUAL_BASE - + EFI_RT_VIRTUAL_SIZE; u32 rnd; status = efi_get_random_bytes(sys_table, sizeof(rnd), |