From: Andrey Ryabinin <aryabinin@virtuozzo.com>
Date: Tue, 17 Jul 2018 16:00:33 +0000 (+0300)
Subject: fuse: Don't access pipe->buffers without pipe_lock()
X-Git-Tag: v3.18.121~14
X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9b39c90f1c2bc7bca594abd10715a4ffe2b16b2c;p=linux

fuse: Don't access pipe->buffers without pipe_lock()

commit a2477b0e67c52f4364a47c3ad70902bc2a61bd4c upstream.

fuse_dev_splice_write() reads pipe->buffers to determine the size of
'bufs' array before taking the pipe_lock(). This is not safe as
another thread might change the 'pipe->buffers' between the allocation
and taking the pipe_lock(). So we end up with too small 'bufs' array.

Move the bufs allocations inside pipe_lock()/pipe_unlock() to fix this.

Fixes: dd3bb14f44a6 ("fuse: support splice() writing to fuse device")
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: <stable@vger.kernel.org> # v2.6.35
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index f2bbb8513360..0834f5640875 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1913,11 +1913,14 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
 	if (!fc)
 		return -EPERM;
 
+	pipe_lock(pipe);
+
 	bufs = kmalloc(pipe->buffers * sizeof(struct pipe_buffer), GFP_KERNEL);
-	if (!bufs)
+	if (!bufs) {
+		pipe_unlock(pipe);
 		return -ENOMEM;
+	}
 
-	pipe_lock(pipe);
 	nbuf = 0;
 	rem = 0;
 	for (idx = 0; idx < pipe->nrbufs && rem < len; idx++)