From 7e588fbc57397daac02cf23677d1849aab7c7507 Mon Sep 17 00:00:00 2001 From: Vincent Fazio Date: Sun, 31 Jan 2021 00:18:49 -0600 Subject: linux-user/elfload: munmap proper address in pgd_find_hole_fallback MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Laurent Vivier Reviewed-by: Alex Bennée Message-Id: <20210131061849.12615-1-vfazio@xes-inc.com> Signed-off-by: Laurent Vivier --- 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 140a971..174ee7b 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -2209,7 +2209,7 @@ 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; -- cgit v1.1