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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jann Horn <jannh@google.com>,
        David Howells <dhowells@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 5.15 094/110] watch_queue, pipe: Free watchqueue state after clearing pipe ring
Date:   Mon, 14 Mar 2022 12:54:36 +0100
Message-Id: <20220314112745.651950510@linuxfoundation.org>
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References: <20220314112743.029192918@linuxfoundation.org>
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From: David Howells <dhowells@redhat.com>

commit db8facfc9fafacefe8a835416a6b77c838088f8b upstream.

In free_pipe_info(), free the watchqueue state after clearing the pipe
ring as each pipe ring descriptor has a release function, and in the
case of a notification message, this is watch_queue_pipe_buf_release()
which tries to mark the allocation bitmap that was previously released.

Fix this by moving the put of the pipe's ref on the watch queue to after
the ring has been cleared.  We still need to call watch_queue_clear()
before doing that to make sure that the pipe is disconnected from any
notification sources first.

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/pipe.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -830,10 +830,8 @@ void free_pipe_info(struct pipe_inode_in
 	int i;
 
 #ifdef CONFIG_WATCH_QUEUE
-	if (pipe->watch_queue) {
+	if (pipe->watch_queue)
 		watch_queue_clear(pipe->watch_queue);
-		put_watch_queue(pipe->watch_queue);
-	}
 #endif
 
 	(void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
@@ -843,6 +841,10 @@ void free_pipe_info(struct pipe_inode_in
 		if (buf->ops)
 			pipe_buf_release(pipe, buf);
 	}
+#ifdef CONFIG_WATCH_QUEUE
+	if (pipe->watch_queue)
+		put_watch_queue(pipe->watch_queue);
+#endif
 	if (pipe->tmp_page)
 		__free_page(pipe->tmp_page);
 	kfree(pipe->bufs);