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authorVitaly Kuznetsov <vkuznets@redhat.com>2016-05-31 11:23:43 +0100
committerIngo Molnar <mingo@kernel.org>2016-06-03 09:57:35 +0200
commit55f1ea15216a5a14c96738bd5284100a00ffa9dc (patch)
treed3632db3b2815f0cdf1c96877d64d27151dc2206 /drivers
parent4340fa55298d17049e71c7a34e04647379c269f3 (diff)
efi: Fix for_each_efi_memory_desc_in_map() for empty memmaps
Commit: 78ce248faa3c ("efi: Iterate over efi.memmap in for_each_efi_memory_desc()") introduced a regression for systems booted with the 'noefi' kernel option. In particular, I observed an early kernel hang in efi_find_mirror()'s for_each_efi_memory_desc() call. As we don't have efi memmap on this system we enter this iterator with the following parameters: efi.memmap.map = 0, efi.memmap.map_end = 0, efi.memmap.desc_size = 28 ... then for_each_efi_memory_desc_in_map() does the following comparison: (md) <= (efi_memory_desc_t *)((m)->map_end - (m)->desc_size); ... where md = 0, (m)->map_end = 0 and (m)->desc_size = 28 but when we subtract something from a NULL pointer wrap around happens and we end up returning invalid pointer and crash. Fix it by using the correct pointer arithmetics. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: K. Y. Srinivasan <kys@microsoft.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mark Salter <msalter@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-efi@vger.kernel.org Fixes: 78ce248faa3c ("efi: Iterate over efi.memmap in for_each_efi_memory_desc()") Link: http://lkml.kernel.org/r/1464690224-4503-2-git-send-email-matt@codeblueprint.co.uk [ Made the changelog more readable. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
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