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 9D0C5258EE7 for ; Mon, 18 Aug 2025 10:47:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755514071; cv=none; b=tEFuxIVYMY/uQrmiEOieSbkhleTnj4i808k9IwHwLTRkNM8MrT8pQ7tVI8P9GaaaEV6lHwWK1lMhQ2tH/tAar7nnLtf75agxdapRXUJr0CEFcso21GqlrniVIse7iUyzEMDFXZVts8+fnsKvVw+BLWZwcTwfqRQMXSOvdm7s4CM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755514071; c=relaxed/simple; bh=OMiAq0HrQtZQc6pIDGA3pPLBw5LbQS7MJDh/PmOimIM=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=GKgtQj4OeDMD9nD9H2px3AhnQ7RU/9Fge7Yi+1JPKLXGAxkd1so/uQHOXJi/NdWtKd427RGgzFmk+WnNKthPVvtNZ1mj7Lf+hjF8l8aPauxFon6DiKWaQHLDswihyqzmgOLoK4KVCcILaiZsSduDBKC4ZQ6R8AwJse2W9xmLwmo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=kaWj9hmm; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="kaWj9hmm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A920EC4CEEB; Mon, 18 Aug 2025 10:47:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755514071; bh=OMiAq0HrQtZQc6pIDGA3pPLBw5LbQS7MJDh/PmOimIM=; h=Subject:To:Cc:From:Date:From; b=kaWj9hmmDwCdPw3Fytby65Y8rMQ89zSQHRgxv2Juu0nHnGrc4gyERMukD8ACueC76 +zwyxAQqhdQqO0OnckzYaU6PAs+A3WN+2affRuJzIW0mWMJAzpDBLPKTCclE1BGEmd puRScOCzDkRf4vu7Uc8USzxKbBDalGLO8Om9jBy0= Subject: FAILED: patch "[PATCH] btrfs: qgroup: fix race between quota disable and quota" failed to apply to 6.1-stable tree To: fdmanana@suse.com,boris@bur.io,dsterba@suse.com,wqu@suse.com,zzzccc427@gmail.com Cc: From: Date: Mon, 18 Aug 2025 12:47:32 +0200 Message-ID: <2025081832-drainable-observant-d242@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 6.1-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-6.1.y git checkout FETCH_HEAD git cherry-pick -x e1249667750399a48cafcf5945761d39fa584edf # git commit -s git send-email --to '' --in-reply-to '2025081832-drainable-observant-d242@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From e1249667750399a48cafcf5945761d39fa584edf Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Mon, 30 Jun 2025 13:19:20 +0100 Subject: [PATCH] btrfs: qgroup: fix race between quota disable and quota rescan ioctl There's a race between a task disabling quotas and another running the rescan ioctl that can result in a use-after-free of qgroup records from the fs_info->qgroup_tree rbtree. This happens as follows: 1) Task A enters btrfs_ioctl_quota_rescan() -> btrfs_qgroup_rescan(); 2) Task B enters btrfs_quota_disable() and calls btrfs_qgroup_wait_for_completion(), which does nothing because at that point fs_info->qgroup_rescan_running is false (it wasn't set yet by task A); 3) Task B calls btrfs_free_qgroup_config() which starts freeing qgroups from fs_info->qgroup_tree without taking the lock fs_info->qgroup_lock; 4) Task A enters qgroup_rescan_zero_tracking() which starts iterating the fs_info->qgroup_tree tree while holding fs_info->qgroup_lock, but task B is freeing qgroup records from that tree without holding the lock, resulting in a use-after-free. Fix this by taking fs_info->qgroup_lock at btrfs_free_qgroup_config(). Also at btrfs_qgroup_rescan() don't start the rescan worker if quotas were already disabled. Reported-by: cen zhang Link: https://lore.kernel.org/linux-btrfs/CAFRLqsV+cMDETFuzqdKSHk_FDm6tneea45krsHqPD6B3FetLpQ@mail.gmail.com/ CC: stable@vger.kernel.org # 6.1+ Reviewed-by: Boris Burkov Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Signed-off-by: David Sterba diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index b83d9534adae..310ca2dd9f24 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -636,22 +636,30 @@ bool btrfs_check_quota_leak(const struct btrfs_fs_info *fs_info) /* * This is called from close_ctree() or open_ctree() or btrfs_quota_disable(), - * first two are in single-threaded paths.And for the third one, we have set - * quota_root to be null with qgroup_lock held before, so it is safe to clean - * up the in-memory structures without qgroup_lock held. + * first two are in single-threaded paths. */ void btrfs_free_qgroup_config(struct btrfs_fs_info *fs_info) { struct rb_node *n; struct btrfs_qgroup *qgroup; + /* + * btrfs_quota_disable() can be called concurrently with + * btrfs_qgroup_rescan() -> qgroup_rescan_zero_tracking(), so take the + * lock. + */ + spin_lock(&fs_info->qgroup_lock); while ((n = rb_first(&fs_info->qgroup_tree))) { qgroup = rb_entry(n, struct btrfs_qgroup, node); rb_erase(n, &fs_info->qgroup_tree); __del_qgroup_rb(qgroup); + spin_unlock(&fs_info->qgroup_lock); btrfs_sysfs_del_one_qgroup(fs_info, qgroup); kfree(qgroup); + spin_lock(&fs_info->qgroup_lock); } + spin_unlock(&fs_info->qgroup_lock); + /* * We call btrfs_free_qgroup_config() when unmounting * filesystem and disabling quota, so we set qgroup_ulist @@ -4036,12 +4044,21 @@ btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info) qgroup_rescan_zero_tracking(fs_info); mutex_lock(&fs_info->qgroup_rescan_lock); - fs_info->qgroup_rescan_running = true; - btrfs_queue_work(fs_info->qgroup_rescan_workers, - &fs_info->qgroup_rescan_work); + /* + * The rescan worker is only for full accounting qgroups, check if it's + * enabled as it is pointless to queue it otherwise. A concurrent quota + * disable may also have just cleared BTRFS_FS_QUOTA_ENABLED. + */ + if (btrfs_qgroup_full_accounting(fs_info)) { + fs_info->qgroup_rescan_running = true; + btrfs_queue_work(fs_info->qgroup_rescan_workers, + &fs_info->qgroup_rescan_work); + } else { + ret = -ENOTCONN; + } mutex_unlock(&fs_info->qgroup_rescan_lock); - return 0; + return ret; } int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info,