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linux-user/elfload: do not assume MAP_FIXED_NOREPLACE kernel support

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Previously, pgd_find_hole_fallback assumed that if the build host's libc
had MAP_FIXED_NOREPLACE defined that the address returned by mmap would
match the requested address. This is not a safe assumption for Linux
kernels prior to 4.17

Now, we always compare mmap's resultant address with the requested
address and no longer short-circuit based on MAP_FIXED_NOREPLACE.

Fixes: 2667e069e7 ("linux-user: don't use MAP_FIXED in pgd_find_hole_fallback")
Signed-off-by: Vincent Fazio <vfazio@gmail.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210131061930.14554-1-vfazio@xes-inc.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Vincent Fazio 2021-01-31 00:19:30 -06:00 committed by Laurent Vivier
parent 7e588fbc57
commit 934eed5178
1 changed files with 1 additions and 2 deletions
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linux-user/elfload.c
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@ -2210,8 +2210,7 @@ static uintptr_t pgd_find_hole_fallback(uintptr_t guest_size, uintptr_t brk,
PROT_NONE, flags, -1, 0); PROT_NONE, flags, -1, 0);
if (mmap_start != MAP_FAILED) { if (mmap_start != MAP_FAILED) {
munmap(mmap_start, guest_size); munmap(mmap_start, guest_size);
if (MAP_FIXED_NOREPLACE != 0 || if (mmap_start == (void *) align_start) {
mmap_start == (void *) align_start) {
return (uintptr_t) mmap_start + offset; return (uintptr_t) mmap_start + offset;
} }
} }