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authorJann Horn <jannh@google.com>2018-10-12 21:34:32 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-10-13 09:31:02 +0200
commit7aa867dd89526e9cfd9714d8b9b587c016eaea34 (patch)
tree0dc7bfaba22b5e268edcfce267a87452aa569943 /mm/mmap.c
parent1cff514a5101d514900f0e94613402d8a18359e6 (diff)
mm/mmap.c: don't clobber partially overlapping VMA with MAP_FIXED_NOREPLACE
Daniel Micay reports that attempting to use MAP_FIXED_NOREPLACE in an application causes that application to randomly crash. The existing check for handling MAP_FIXED_NOREPLACE looks up the first VMA that either overlaps or follows the requested region, and then bails out if that VMA overlaps *the start* of the requested region. It does not bail out if the VMA only overlaps another part of the requested region. Fix it by checking that the found VMA only starts at or after the end of the requested region, in which case there is no overlap. Test case: user@debian:~$ cat mmap_fixed_simple.c #include <sys/mman.h> #include <errno.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #ifndef MAP_FIXED_NOREPLACE #define MAP_FIXED_NOREPLACE 0x100000 #endif int main(void) { char *p; errno = 0; p = mmap((void*)0x10001000, 0x4000, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED_NOREPLACE, -1, 0); printf("p1=%p err=%m\n", p); errno = 0; p = mmap((void*)0x10000000, 0x2000, PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED_NOREPLACE, -1, 0); printf("p2=%p err=%m\n", p); char cmd[100]; sprintf(cmd, "cat /proc/%d/maps", getpid()); system(cmd); return 0; } user@debian:~$ gcc -o mmap_fixed_simple mmap_fixed_simple.c user@debian:~$ ./mmap_fixed_simple p1=0x10001000 err=Success p2=0x10000000 err=Success 10000000-10002000 r--p 00000000 00:00 0 10002000-10005000 ---p 00000000 00:00 0 564a9a06f000-564a9a070000 r-xp 00000000 fe:01 264004 /home/user/mmap_fixed_simple 564a9a26f000-564a9a270000 r--p 00000000 fe:01 264004 /home/user/mmap_fixed_simple 564a9a270000-564a9a271000 rw-p 00001000 fe:01 264004 /home/user/mmap_fixed_simple 564a9a54a000-564a9a56b000 rw-p 00000000 00:00 0 [heap] 7f8eba447000-7f8eba5dc000 r-xp 00000000 fe:01 405885 /lib/x86_64-linux-gnu/libc-2.24.so 7f8eba5dc000-7f8eba7dc000 ---p 00195000 fe:01 405885 /lib/x86_64-linux-gnu/libc-2.24.so 7f8eba7dc000-7f8eba7e0000 r--p 00195000 fe:01 405885 /lib/x86_64-linux-gnu/libc-2.24.so 7f8eba7e0000-7f8eba7e2000 rw-p 00199000 fe:01 405885 /lib/x86_64-linux-gnu/libc-2.24.so 7f8eba7e2000-7f8eba7e6000 rw-p 00000000 00:00 0 7f8eba7e6000-7f8eba809000 r-xp 00000000 fe:01 405876 /lib/x86_64-linux-gnu/ld-2.24.so 7f8eba9e9000-7f8eba9eb000 rw-p 00000000 00:00 0 7f8ebaa06000-7f8ebaa09000 rw-p 00000000 00:00 0 7f8ebaa09000-7f8ebaa0a000 r--p 00023000 fe:01 405876 /lib/x86_64-linux-gnu/ld-2.24.so 7f8ebaa0a000-7f8ebaa0b000 rw-p 00024000 fe:01 405876 /lib/x86_64-linux-gnu/ld-2.24.so 7f8ebaa0b000-7f8ebaa0c000 rw-p 00000000 00:00 0 7ffcc99fa000-7ffcc9a1b000 rw-p 00000000 00:00 0 [stack] 7ffcc9b44000-7ffcc9b47000 r--p 00000000 00:00 0 [vvar] 7ffcc9b47000-7ffcc9b49000 r-xp 00000000 00:00 0 [vdso] ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall] user@debian:~$ uname -a Linux debian 4.19.0-rc6+ #181 SMP Wed Oct 3 23:43:42 CEST 2018 x86_64 GNU/Linux user@debian:~$ As you can see, the first page of the mapping at 0x10001000 was clobbered. Link: http://lkml.kernel.org/r/20181010152736.99475-1-jannh@google.com Fixes: a4ff8e8620d3 ("mm: introduce MAP_FIXED_NOREPLACE") Signed-off-by: Jann Horn <jannh@google.com> Reported-by: Daniel Micay <danielmicay@gmail.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: John Hubbard <jhubbard@nvidia.com> Acked-by: Kees Cook <keescook@chromium.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r--mm/mmap.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 5f2b2b184c60..f7cd9cb966c0 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1410,7 +1410,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
if (flags & MAP_FIXED_NOREPLACE) {
struct vm_area_struct *vma = find_vma(mm, addr);
- if (vma && vma->vm_start <= addr)
+ if (vma && vma->vm_start < addr + len)
return -EEXIST;
}