linux-kernel - [PATCH] pipe: Fix iteration end check in fuse_dev_splice

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Message-ID: <157566809107.17007.16619855857308884231.stgit@warthog.procyon.org.uk>
Date:   Fri, 06 Dec 2019 21:34:51 +0000
From:   David Howells <dhowells@...hat.com>
To:     torvalds@...ux-foundation.org
Cc:     miklos@...redi.hu, dhowells@...hat.com, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] pipe: Fix iteration end check in fuse_dev_splice_write()

Fix the iteration end check in fuse_dev_splice_write().  The iterator
position can only be compared with == or != since wrappage may be involved.

Fixes: 8cefc107ca54 ("pipe: Use head and tail pointers for the ring, not cursor and length")
Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/fuse/dev.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index d4e6691d2d92..8e02d76fe104 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1965,7 +1965,7 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
 
 	nbuf = 0;
 	rem = 0;
-	for (idx = tail; idx < head && rem < len; idx++)
+	for (idx = tail; idx != head && rem < len; idx++)
 		rem += pipe->bufs[idx & mask].len;
 
 	ret = -EINVAL;