elf: fix NT_FILE integer overflow

Web:        https://git.kernel.org/torvalds/c/60c9d92f887f4606d363fece7a36c92664dc64c6
Commit:     60c9d92f887f4606d363fece7a36c92664dc64c6
Parent:     2d453e3b41c80d1a2c02b02d672f5dcd73f95a12
Refname:    refs/heads/master
Author:     Alexey Dobriyan <[email protected]>
AuthorDate: Tue Feb 6 15:39:13 2018 -0800
Committer:  Linus Torvalds <[email protected]>
CommitDate: Tue Feb 6 18:32:45 2018 -0800

    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 <[email protected]>
    Signed-off-by: Andrew Morton <[email protected]>
    Signed-off-by: Linus Torvalds <[email protected]>
---
 fs/binfmt_elf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 83732fef510d..bdb201230bae 100644
--- 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]);
--
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