Le 31/01/2021 à 07:18, Vincent Fazio a écrit :
> From: Vincent Fazio <vfa...@gmail.com>
Please, use the same email address to send your patch.
>
> Previously, if the build host's libc did not define MAP_FIXED_NOREPLACE
> or if the running kernel didn't support that flag, it was possible for
> pgd_find_hole_fallback to munmap an incorrect address which could lead to
> SIGSEGV if the range happened to overlap with the mapped address of the
> QEMU binary.
>
> mmap(0x1000, 22261224, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
> -1, 0) = 0x7f889d331000
> munmap(0x1000, 22261224) = 0
> --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0x84b817} ---
> ++ killed by SIGSEGV +++
>
> Now, always munmap the address returned by mmap.
>
> Fixes: 2667e069e7b5 ("linux-user: don't use MAP_FIXED in
> pgd_find_hole_fallback")
> Signed-off-by: Vincent Fazio <vfa...@gmail.com>
> ---
> linux-user/elfload.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index a64050713f..5f5f23d2e5 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -2216,7 +2216,7 @@ static uintptr_t pgd_find_hole_fallback(uintptr_t
> guest_size, uintptr_t brk,
> void * mmap_start = mmap((void *) align_start, guest_size,
> PROT_NONE, flags, -1, 0);
> if (mmap_start != MAP_FAILED) {
> - munmap((void *) align_start, guest_size);
> + munmap(mmap_start, guest_size);
> if (MAP_FIXED_NOREPLACE != 0 ||
> mmap_start == (void *) align_start) {
> return (uintptr_t) mmap_start + offset;
>
Reviewed-by: Laurent Vivier <laur...@vivier.eu>
CC: Alex
Thanks,
Laurent
