From: Vitaly Kuznetsov Date: Tue, 31 May 2016 10:23:43 +0000 (+0100) Subject: efi: Fix for_each_efi_memory_desc_in_map() for empty memmaps X-Git-Tag: v4.7-rc3~17^2~1 X-Git-Url: http://git.cascardo.eti.br/?a=commitdiff_plain;h=55f1ea15216a5a14c96738bd5284100a00ffa9dc;p=cascardo%2Flinux.git 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 Signed-off-by: Matt Fleming Cc: Ard Biesheuvel Cc: K. Y. Srinivasan Cc: Linus Torvalds Cc: Mark Salter Cc: Peter Zijlstra Cc: Thomas Gleixner 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 --- diff --git a/include/linux/efi.h b/include/linux/efi.h index c2db3ca22217..f196dd0b0f2f 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1005,7 +1005,7 @@ extern int efi_memattr_apply_permissions(struct mm_struct *mm, /* Iterate through an efi_memory_map */ #define for_each_efi_memory_desc_in_map(m, md) \ for ((md) = (m)->map; \ - (md) <= (efi_memory_desc_t *)((m)->map_end - (m)->desc_size); \ + ((void *)(md) + (m)->desc_size) <= (m)->map_end; \ (md) = (void *)(md) + (m)->desc_size) /**