elf: fix NT_FILE integer overflow

If vm.max_map_count bumped above 2^26 (67+ mil) and system has enough RAM
to allocate all the VMAs (~12.8 GB on Fedora 27 with 200-byte VMAs), then
it should be possible to overflow 32-bit "size", pass paranoia check,
allocate very little vmalloc space and oops while writing into vmalloc
guard page...

But I didn't test this, only coredump of regular process.

Link: http://lkml.kernel.org/r/20180112203427.GA9109@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 83732fef510d284032a16fb2f7b95c4f94ad1dd3..bdb201230bae93c408cf1972b6f9bb92ad37e478 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1599,6 +1599,8 @@ static int fill_files_note(struct memelfnote *note)
 
        /* *Estimated* file count and total data size needed */
        count = current->mm->map_count;
+       if (count > UINT_MAX / 64)
+               return -EINVAL;
        size = count * 64;
 
        names_ofs = (2 + 3 * count) * sizeof(data[0]);