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From: Miklos Szeredi on 8 Jun 2010 10:30
From: Miklos Szeredi <mszeredi(a)suse.cz>

pipe_set_size() needs to copy pipe bufs from the old circular buffer
to the new.

The current code gets this wrong in multiple ways, resulting in oops.

Test program is available here:
http://www.kernel.org/pub/linux/kernel/people/mszeredi/piperesize/

Signed-off-by: Miklos Szeredi <mszeredi(a)suse.cz>
---
fs/pipe.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

Index: linux.git/fs/pipe.c
===================================================================
--- linux.git.orig/fs/pipe.c 2010-06-08 15:02:16.000000000 +0200
+++ linux.git/fs/pipe.c 2010-06-08 15:50:07.000000000 +0200
@@ -1145,13 +1145,20 @@ static long pipe_set_size(struct pipe_in
* and adjust the indexes.
*/
if (pipe->nrbufs) {
- const unsigned int tail = pipe->nrbufs & (pipe->buffers - 1);
- const unsigned int head = pipe->nrbufs - tail;
+ unsigned int tail;
+ unsigned int head;

+ tail = pipe->curbuf + pipe->nrbufs;
+ if (tail < pipe->buffers)
+ tail = 0;
+ else
+ tail &= (pipe->buffers - 1);
+
+ head = pipe->nrbufs - tail;
if (head)
memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
if (tail)
- memcpy(bufs + head, pipe->bufs + pipe->curbuf, tail * sizeof(struct pipe_buffer));
+ memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
}

pipe->curbuf = 0;
--
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