Fix missing sanity check in /dev/sg

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commit 137d01df51 upstream.

What happens is that a write to /dev/sg is given a request with non-zero
->iovec_count combined with zero ->dxfer_len.  Or with ->dxferp pointing
to an array full of empty iovecs.

Having write permission to /dev/sg shouldn't be equivalent to the
ability to trigger BUG_ON() while holding spinlocks...

Found by Dmitry Vyukov and syzkaller.

[ The BUG_ON() got changed to a WARN_ON_ONCE(), but this fixes the
  underlying issue.  - Linus ]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.16: we're not using iov_iter, but can check the
 byte length after truncation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

...

This commit is contained in:

Al Viro 2017-02-19 07:15:27 +00:00 • committed by Ben Hutchings

parent e5ca28d1c3

commit 41abcae496

1 changed files with 4 additions and 0 deletions

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drivers/scsi/sg.c

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