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fix invalid read in aligned_alloc

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in case of mmap-obtained chunks, end points past the end of the
mapping and reading it may fault. since the value is not needed until
after the conditional, move the access to prevent invalid reads.
This commit is contained in:
Rich Felker 2012-12-06 21:12:28 -05:00
parent 5c5e45e58b
commit 2ad9cf52eb
1 changed files with 3 additions and 2 deletions
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5
src/malloc/aligned_alloc.c
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@ -31,8 +31,6 @@ void *aligned_alloc(size_t align, size_t len)
return NULL;
header = ((size_t *)mem)[-1];
end = mem + (header & -8);
footer = ((size_t *)end)[-2];
new = (void *)((uintptr_t)mem + align-1 & -align);
if (!(header & 7)) {
@ -41,6 +39,9 @@ void *aligned_alloc(size_t align, size_t len)
return new;
}
end = mem + (header & -8);
footer = ((size_t *)end)[-2];
((size_t *)mem)[-1] = header&7 | new-mem;
((size_t *)new)[-2] = footer&7 | new-mem;
((size_t *)new)[-1] = header&7 | end-new;