efi/libstub/arm: Don't use TASK_SIZE when randomizing the RT space
As reported by James, Catalin and Mark, commit: e69176d6 ("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.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>
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