From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Fleming Subject: [PATCH 1/2] efi: Fix for_each_efi_memory_desc_in_map() for empty memmaps Date: Tue, 31 May 2016 11:23:43 +0100 Message-ID: <1464690224-4503-2-git-send-email-matt@codeblueprint.co.uk> References: <1464690224-4503-1-git-send-email-matt@codeblueprint.co.uk> Return-path: In-Reply-To: <1464690224-4503-1-git-send-email-matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ingo Molnar , Thomas Gleixner , "H . Peter Anvin" Cc: Vitaly Kuznetsov , Ard Biesheuvel , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Matt Fleming , "K. Y. Srinivasan" , Mark Salter List-Id: linux-efi@vger.kernel.org From: Vitaly Kuznetsov Commit 78ce248faa3c ("efi: Iterate over efi.memmap in for_each_efi_memory_desc()") introduced a regression for systems booted with 'noefi' kernel option. In particular, I observe early kernel hang in efi_find_mirror() on for_each_efi_memory_desc() call. As we don't have efi memmap we enter this iterator with the following parameters: efi.memmap.map = 0, efi.memmap.map_end = 0, efi.memmap.desc_size = 28 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. Fixes: 78ce248faa3c ("efi: Iterate over efi.memmap in for_each_efi_memory_desc()") Signed-off-by: Vitaly Kuznetsov Cc: Mark Salter Cc: "K. Y. Srinivasan" Signed-off-by: Matt Fleming --- include/linux/efi.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) 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) /** -- 2.7.3