Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 08/22] Fix missing sanity check in /dev/sg | Date | Tue, 21 Feb 2017 14:03:22 +0100 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Al Viro <viro@ZenIV.linux.org.uk>
commit 137d01df511b3afe1f05499aea05f3bafc0fb221 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/scsi/sg.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1753,6 +1753,10 @@ sg_start_req(Sg_request *srp, unsigned c return res; iov_iter_truncate(&i, hp->dxfer_len); + if (!iov_iter_count(&i)) { + kfree(iov); + return -EINVAL; + } res = blk_rq_map_user_iov(q, rq, md, &i, GFP_ATOMIC); kfree(iov);
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