From: Vincent Fazio Date: Sun, 31 Jan 2021 06:19:30 +0000 (-0600) Subject: linux-user/elfload: do not assume MAP_FIXED_NOREPLACE kernel support X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=934eed517857ce2de9a8a92c2599612581b4eb4a;p=qemu.git linux-user/elfload: do not assume MAP_FIXED_NOREPLACE kernel support 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: 2667e069e7b5 ("linux-user: don't use MAP_FIXED in pgd_find_hole_fallback") Signed-off-by: Vincent Fazio Reviewed-by: Laurent Vivier Reviewed-by: Alex Bennée Message-Id: <20210131061930.14554-1-vfazio@xes-inc.com> Signed-off-by: Laurent Vivier --- diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 174ee7bad6..e525901659 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -2210,8 +2210,7 @@ static uintptr_t pgd_find_hole_fallback(uintptr_t guest_size, uintptr_t brk, PROT_NONE, flags, -1, 0); if (mmap_start != MAP_FAILED) { munmap(mmap_start, guest_size); - if (MAP_FIXED_NOREPLACE != 0 || - mmap_start == (void *) align_start) { + if (mmap_start == (void *) align_start) { return (uintptr_t) mmap_start + offset; } }