Commit-ID: 55f1ea15216a5a14c96738bd5284100a00ffa9dc
Gitweb: http://git.kernel.org/tip/55f1ea15216a5a14c96738bd5284100a00ffa9dc
Author: Vitaly Kuznetsov <vkuzn...@redhat.com>
AuthorDate: Tue, 31 May 2016 11:23:43 +0100
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Fri, 3 Jun 2016 09:57:35 +0200
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 <vkuzn...@redhat.com>
Signed-off-by: Matt Fleming <m...@codeblueprint.co.uk>
Cc: Ard Biesheuvel <ard.biesheu...@linaro.org>
Cc: K. Y. Srinivasan <k...@microsoft.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Mark Salter <msal...@redhat.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: linux-...@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-m...@codeblueprint.co.uk
[ Made the changelog more readable. ]
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
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 c2db3ca..f196dd0 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)
/**
