This is a note to let you know that I've just added the patch titled
Fix thinko in iov_iter_single_seg_count
to the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fix-thinko-in-iov_iter_single_seg_count.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ad0eab9293485d1c06237e9249f6d4dfa3d93d4d Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@xxxxxxxxx>
Date: Thu, 13 Nov 2014 20:15:23 +1100
Subject: Fix thinko in iov_iter_single_seg_count
From: Paul Mackerras <paulus@xxxxxxxxx>
commit ad0eab9293485d1c06237e9249f6d4dfa3d93d4d upstream.
The branches of the if (i->type & ITER_BVEC) statement in
iov_iter_single_seg_count() are the wrong way around; if ITER_BVEC is
clear then we use i->bvec, when we should be using i->iov. This fixes
it.
In my case, the symptom that this caused was that a KVM guest doing
filesystem operations on a virtual disk would result in one of qemu's
threads on the host going into an infinite loop in
generic_perform_write(). The loop would hit the copied == 0 case and
call iov_iter_single_seg_count() to reduce the number of bytes to try
to process, but because of the error, iov_iter_single_seg_count()
would just return i->count and the loop made no progress and continued
forever.
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/iov_iter.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -699,9 +699,9 @@ size_t iov_iter_single_seg_count(const s
if (i->nr_segs == 1)
return i->count;
else if (i->type & ITER_BVEC)
- return min(i->count, i->iov->iov_len - i->iov_offset);
- else
return min(i->count, i->bvec->bv_len - i->iov_offset);
+ else
+ return min(i->count, i->iov->iov_len - i->iov_offset);
}
EXPORT_SYMBOL(iov_iter_single_seg_count);
Patches currently in stable-queue which might be from paulus@xxxxxxxxx are
queue-3.17/fix-thinko-in-iov_iter_single_seg_count.patch
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