From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 043B78F5B for ; Sun, 16 Jul 2023 20:27:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7E0A1C433C8; Sun, 16 Jul 2023 20:27:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689539237; bh=sAvxDAvpZIGEhfezrcwVQoH/pX2QTjTEtDwlUABkclQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=x+0Y5Z/JaeVG1UaGhM4UsRL9ElvKrbUV1BoH2ld0ZbiNpS6Uy1AgrGsP70vC+eENQ KHLRg68EpyKME9vYjblyCyMsoucbzL2NMD9+2+p2ZOgKAUQKcj/p1PwmHn8C5ZXCd9 T9AB3Vgu/nbR04ro9hEVRHb90Zq16n6k+IDWp1nI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Siddh Raman Pant , David Howells , Christian Brauner Subject: [PATCH 6.4 737/800] watch_queue: prevent dangling pipe pointer Date: Sun, 16 Jul 2023 21:49:50 +0200 Message-ID: <20230716195006.235853293@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230716194949.099592437@linuxfoundation.org> References: <20230716194949.099592437@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Siddh Raman Pant commit 943211c87427f25bd22e0e63849fb486bb5f87fa upstream. NULL the dangling pipe reference while clearing watch_queue. If not done, a reference to a freed pipe remains in the watch_queue, as this function is called before freeing a pipe in free_pipe_info() (see line 834 of fs/pipe.c). The sole use of wqueue->defunct is for checking if the watch queue has been cleared, but wqueue->pipe is also NULLed while clearing. Thus, wqueue->defunct is superfluous, as wqueue->pipe can be checked for NULL. Hence, the former can be removed. Tested with keyutils testsuite. Cc: stable@vger.kernel.org # 6.1 Signed-off-by: Siddh Raman Pant Acked-by: David Howells Message-Id: <20230605143616.640517-1-code@siddh.me> Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman --- include/linux/watch_queue.h | 3 +-- kernel/watch_queue.c | 12 ++++++------ 2 files changed, 7 insertions(+), 8 deletions(-) --- a/include/linux/watch_queue.h +++ b/include/linux/watch_queue.h @@ -38,7 +38,7 @@ struct watch_filter { struct watch_queue { struct rcu_head rcu; struct watch_filter __rcu *filter; - struct pipe_inode_info *pipe; /* The pipe we're using as a buffer */ + struct pipe_inode_info *pipe; /* Pipe we use as a buffer, NULL if queue closed */ struct hlist_head watches; /* Contributory watches */ struct page **notes; /* Preallocated notifications */ unsigned long *notes_bitmap; /* Allocation bitmap for notes */ @@ -46,7 +46,6 @@ struct watch_queue { spinlock_t lock; unsigned int nr_notes; /* Number of notes */ unsigned int nr_pages; /* Number of pages in notes[] */ - bool defunct; /* T when queues closed */ }; /* --- a/kernel/watch_queue.c +++ b/kernel/watch_queue.c @@ -42,7 +42,7 @@ MODULE_AUTHOR("Red Hat, Inc."); static inline bool lock_wqueue(struct watch_queue *wqueue) { spin_lock_bh(&wqueue->lock); - if (unlikely(wqueue->defunct)) { + if (unlikely(!wqueue->pipe)) { spin_unlock_bh(&wqueue->lock); return false; } @@ -104,9 +104,6 @@ static bool post_one_notification(struct unsigned int head, tail, mask, note, offset, len; bool done = false; - if (!pipe) - return false; - spin_lock_irq(&pipe->rd_wait.lock); mask = pipe->ring_size - 1; @@ -603,8 +600,11 @@ void watch_queue_clear(struct watch_queu rcu_read_lock(); spin_lock_bh(&wqueue->lock); - /* Prevent new notifications from being stored. */ - wqueue->defunct = true; + /* + * This pipe can be freed by callers like free_pipe_info(). + * Removing this reference also prevents new notifications. + */ + wqueue->pipe = NULL; while (!hlist_empty(&wqueue->watches)) { watch = hlist_entry(wqueue->watches.first, struct watch, queue_node);