From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792594125; b=RZIaVLUfu/uDhifKNz+PIpKWbFj4aXehwZbI5dXsb64rPkZoIuLRa2NFop6obAvFp0az baiUGizuzd9qivQj6qEEYNHvLKn6yL/HxoohF/3Zsf2WK8v2UB0SE56rohIEpouOxCu2B oFvYlJBpBWO5/XgTPH8Qs5Dqnc+n4dMaF4lRHW6sJA3G+bbByWsEmj+494os24DCIfWsh oMS8Ar6Oo7bCvYCLjqYLb2MEIdHF+b7YkrP3y8Bz5INz5AIkm+YqQJnci2c7bz7d14iGT 66J0du3F7hbq8oWW959O5/u+QVMFW7rDy0IOdkUHHpRWg40lyjehvds80rMx7MoRsuQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792594125; h=Received:DKIM-Signature:Subject:To:Cc:From:Date:Message-ID: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=xXMv4E7+NL6Qc9RBuiYMZAGQJseXFO9aN6xy3Bx0ye8=; b=YBeRBUsrUoOLGOEqb81nR7gYgIJY0fHYeBQm8GW2O/FBRXSnk7z22GoevDjkS6gxqZh4 UqWa4a8waA8le1+JUQpPDH2LFq1LRnhfqDwqf8xL5BzV+RRM+e3Tzul2/woWquKeMxAkY i6gScHSePIIpGDwRDvYEIh8PR8t5W73XNdt9dEvEqNMoF8XfQLShzG/YILkx5jvdNXkX0 QFfuvpBnMWwP84zyLcyHGumtHvFXZ7lICJo3T4v/O/3Fz5E2wf+PjD6dW/gLrjx68+o3r ZA//3FICi+BJkCHChQlQTXAGsJvjFvoypxhCqjDM3XbLdjs+lTxtUrBQX7Pky4s3mWg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=PgJR85Um; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4632A606A31A for ; Wed, 21 Oct 2026 14:48:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=PgJR85Um Received: by smtp.kernel.org (Postfix) with ESMTPSA id 611FD1F000C2; Wed, 21 Oct 2026 14:48:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792594124; bh=xXMv4E7+NL6Qc9RBuiYMZAGQJseXFO9aN6xy3Bx0ye8=; h=Subject:To:Cc:From:Date; b=PgJR85UmF6DJ5N+M+F+2M8f5MTkUuixJXNj/a7tgto2xqazT9I0fGuNF5gPibsfZD z6QS541vpJtG1wlf13SSEbjuc0CS/yEU+NHHxMVIuoI3XKrhTLNLDas+r6NkNQ5rLq DkL2lwKtS4UrQmSLi9hWOoWk4DmC8suupeecGr9c= Subject: FAILED: patch "[PATCH] watch_queue: Fix note pool publication race in" failed to apply to 6.6-stable tree To: cenzhang@linux.microsoft.com,brads@mainlining.org,brauner@kernel.org,stable@vger.kernel.org,threeearcat@gmail.com Cc: From: Date: Wed, 21 Oct 2026 16:34:21 +0200 Message-ID: <2026102121-dial-citric-080a@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 5e531d62f1f8834faf7a4eed0d41105cf6570a8f # git commit -s git send-email --to '' --in-reply-to '2026102121-dial-citric-080a@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 5e531d62f1f8834faf7a4eed0d41105cf6570a8f Mon Sep 17 00:00:00 2001 From: "Cen Zhang (Microsoft)" Date: Fri, 9 Oct 2026 18:47:15 -0400 Subject: [PATCH] watch_queue: Fix note pool publication race in watch_queue_set_size() There is a race between watch_queue_set_size() and post_one_notification(). watch_queue_set_size() publishes wqueue->notes, notes_bitmap, nr_pages and nr_notes with plain stores, and post_one_notification() reads them with plain loads under a different lock, so nothing orders the four stores against the poster's loads: depending on the build, notes can be stored last (gcc 14 on x86-64 does this). Since keyctl_watch_key() lets a watch attach to a queue before it is sized, post_one_notification() can already be running on another CPU at that moment: it reads nr_notes > 0, passes its bounds check, and then reads notes while it is still NULL, dereferencing notes[0]. An unprivileged user triggers this reliably by watching one of its own keys through a notification pipe and racing ioctl(IOC_WATCH_QUEUE_SET_SIZE) on that pipe against keyctl(KEYCTL_SETPERM) on the key from another CPU, triggering: BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: 0010:post_one_notification.isra.0+0xa2/0x1e0 Call Trace: __post_watch_notification+0x148/0x180 keyctl_setperm_key+0x119/0x130 do_syscall_64+0x108/0x4c0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Kernel panic - not syncing: Fatal exception in interrupt Fix this by publishing nr_notes last with smp_store_release(), and by reading it once with smp_load_acquire() in post_one_notification() before the bitmap and the page array are touched. A poster that observes a non-zero nr_notes then also observes the pool behind it; one that observes zero drops the notification as before. Fixes: c73be61cede5 ("pipe: Add general notification queue support") Reported-by: Dae R. Jeong Closes: https://lore.kernel.org/all/ZT-S8Q7tyutcvu_q@dragonet/ Reported-by: AutonomousCodeSecurity@microsoft.com Suggested-by: Dae R. Jeong Signed-off-by: Cen Zhang (Microsoft) Link: https://patch.msgid.link/20261009224715.46121-1-cenzhang@linux.microsoft.com Reviewed-by: Bradley Morgan Cc: Signed-off-by: Christian Brauner (Amutable) diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c index 538520861e8b..932a88ac1f39 100644 --- a/kernel/watch_queue.c +++ b/kernel/watch_queue.c @@ -101,7 +101,7 @@ static bool post_one_notification(struct watch_queue *wqueue, struct pipe_inode_info *pipe = wqueue->pipe; struct pipe_buffer *buf; struct page *page; - unsigned int head, tail, note, offset, len; + unsigned int head, tail, note, offset, len, nr_notes; bool done = false; spin_lock_irq(&pipe->rd_wait.lock); @@ -111,8 +111,10 @@ static bool post_one_notification(struct watch_queue *wqueue, if (pipe_full(head, tail, pipe->ring_size)) goto lost; - note = find_first_bit(wqueue->notes_bitmap, wqueue->nr_notes); - if (note >= wqueue->nr_notes) + /* Pairs with the smp_store_release() in watch_queue_set_size(). */ + nr_notes = smp_load_acquire(&wqueue->nr_notes); + note = find_first_bit(wqueue->notes_bitmap, nr_notes); + if (note >= nr_notes) goto lost; page = wqueue->notes[note / WATCH_QUEUE_NOTES_PER_PAGE]; @@ -297,7 +299,8 @@ long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes) wqueue->notes = pages; wqueue->notes_bitmap = bitmap; wqueue->nr_pages = nr_pages; - wqueue->nr_notes = nr_notes; + /* Pairs with the smp_load_acquire() in post_one_notification(). */ + smp_store_release(&wqueue->nr_notes, nr_notes); return 0; error_p: