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 6834215956D; Mon, 29 Jan 2024 17:09:37 +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=1706548177; cv=none; b=ndi3CPmC3lhnMuo9q2mS8izymj/xDXGpI8ittH8GbeWX/MVUpWZ6xZEehraoPyPEe6mE2qFQpD9BaGYtNDXstJTdJ5vUct0z5IiA71WgS+wWW+G9I4wnFZzYMMO6cTBiN8BUz0zkPdgmpGFFKKwVactDoelf73iAnuGvYKVCX80= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706548177; c=relaxed/simple; bh=WIK6Yv4m+6bjfti8JQUSmf0HznD7BsA3s0QonZHUauQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nAEYFzqU6cj/bdNIFaprcdlAL371o6wB8SESd71tvzuJMSpFSw2qod/OIXLZymJQd3zwIeNczlZLCpWSl7TST880gaShdnXKq5MxS8w+lfSu2gtBJPWWlke2UskOCbUJ2zU7QF8IiuHZuT7eXz878fgyCKvUmPDc/LINTlUeFsI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=R5aXWLyu; 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="R5aXWLyu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2FD61C433F1; Mon, 29 Jan 2024 17:09:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1706548177; bh=WIK6Yv4m+6bjfti8JQUSmf0HznD7BsA3s0QonZHUauQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=R5aXWLyuj+sk1rZIvH+YHca0kmUsJWMTZHDG2LYilxDn4wOVZ6rpU4vwgf14WOfAG EIKeq3Z0j8te/cEUuEdOeF7srNSOdhidSD3jPKLcZY2jNEnLqKMiMgndHLgopc+NxA Bc+NePli6JQvcLEAZ7KGOB9hRr3SxyohzbtIas3Q= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sweet Tea Dorminy , Anand Jain , Omar Sandoval , David Sterba Subject: [PATCH 6.7 223/346] btrfs: avoid copying BTRFS_ROOT_SUBVOL_DEAD flag to snapshot of subvolume being deleted Date: Mon, 29 Jan 2024 09:04:14 -0800 Message-ID: <20240129170022.950114557@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240129170016.356158639@linuxfoundation.org> References: <20240129170016.356158639@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.7-stable review patch. If anyone has any objections, please let me know. ------------------ From: Omar Sandoval commit 3324d0547861b16cf436d54abba7052e0c8aa9de upstream. Sweet Tea spotted a race between subvolume deletion and snapshotting that can result in the root item for the snapshot having the BTRFS_ROOT_SUBVOL_DEAD flag set. The race is: Thread 1 | Thread 2 ----------------------------------------------|---------- btrfs_delete_subvolume | btrfs_set_root_flags(BTRFS_ROOT_SUBVOL_DEAD)| |btrfs_mksubvol | down_read(subvol_sem) | create_snapshot | ... | create_pending_snapshot | copy root item from source down_write(subvol_sem) | This flag is only checked in send and swap activate, which this would cause to fail mysteriously. create_snapshot() now checks the root refs to reject a deleted subvolume, so we can fix this by locking subvol_sem earlier so that the BTRFS_ROOT_SUBVOL_DEAD flag and the root refs are updated atomically. CC: stable@vger.kernel.org # 4.14+ Reported-by: Sweet Tea Dorminy Reviewed-by: Sweet Tea Dorminy Reviewed-by: Anand Jain Signed-off-by: Omar Sandoval Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/inode.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -4449,6 +4449,8 @@ int btrfs_delete_subvolume(struct btrfs_ u64 root_flags; int ret; + down_write(&fs_info->subvol_sem); + /* * Don't allow to delete a subvolume with send in progress. This is * inside the inode lock so the error handling that has to drop the bit @@ -4460,25 +4462,25 @@ int btrfs_delete_subvolume(struct btrfs_ btrfs_warn(fs_info, "attempt to delete subvolume %llu during send", dest->root_key.objectid); - return -EPERM; + ret = -EPERM; + goto out_up_write; } if (atomic_read(&dest->nr_swapfiles)) { spin_unlock(&dest->root_item_lock); btrfs_warn(fs_info, "attempt to delete subvolume %llu with active swapfile", root->root_key.objectid); - return -EPERM; + ret = -EPERM; + goto out_up_write; } root_flags = btrfs_root_flags(&dest->root_item); btrfs_set_root_flags(&dest->root_item, root_flags | BTRFS_ROOT_SUBVOL_DEAD); spin_unlock(&dest->root_item_lock); - down_write(&fs_info->subvol_sem); - ret = may_destroy_subvol(dest); if (ret) - goto out_up_write; + goto out_undead; btrfs_init_block_rsv(&block_rsv, BTRFS_BLOCK_RSV_TEMP); /* @@ -4488,7 +4490,7 @@ int btrfs_delete_subvolume(struct btrfs_ */ ret = btrfs_subvolume_reserve_metadata(root, &block_rsv, 5, true); if (ret) - goto out_up_write; + goto out_undead; trans = btrfs_start_transaction(root, 0); if (IS_ERR(trans)) { @@ -4554,15 +4556,17 @@ out_end_trans: inode->i_flags |= S_DEAD; out_release: btrfs_subvolume_release_metadata(root, &block_rsv); -out_up_write: - up_write(&fs_info->subvol_sem); +out_undead: if (ret) { spin_lock(&dest->root_item_lock); root_flags = btrfs_root_flags(&dest->root_item); btrfs_set_root_flags(&dest->root_item, root_flags & ~BTRFS_ROOT_SUBVOL_DEAD); spin_unlock(&dest->root_item_lock); - } else { + } +out_up_write: + up_write(&fs_info->subvol_sem); + if (!ret) { d_invalidate(dentry); btrfs_prune_dentries(dest); ASSERT(dest->send_in_progress == 0);