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x86/e820: Fix very large 'size' handling boundary condition

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The (start, size) tuple represents a range [start, start + size - 1],
which means "start" and "start + size - 1" should be compared to see
whether the range overflows.

For example, a range with (start, size):

	(0xffffffff fffffff0, 0x00000000 00000010)

represents

	[0xffffffff fffffff0, 0xffffffff ffffffff]

... would be judged overflow in the original code, while actually it is not.

This patch fixes this and makes sure it still works when size is zero.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: yinghai@kernel.org
Link: http://lkml.kernel.org/r/1471657213-31817-1-git-send-email-richard.weiyang@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Wei Yang 2016-08-20 01:40:13 +00:00 • committed by Ingo Molnar
commit 3ec979658e
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kernel/e820.c
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@ -388,11 +388,11 @@ static int __init __append_e820_map(struct e820entry *biosmap, int nr_map)
while (nr_map) {
u64 start = biosmap->addr;
u64 size = biosmap->size;
u64 end = start + size;
u64 end = start + size - 1;
u32 type = biosmap->type;
/* Overflow in 64 bits? Ignore the memory map. */
if (start > end)
if (start > end && likely(size))
return -1;
e820_add_region(start, size, type);