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 687AB779F8; Wed, 21 Feb 2024 13:28:07 +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=1708522087; cv=none; b=Xrsr0Zvbwyj0IJbjJRAVwEOB4H58GPMDVfeNgCXMmlaFkN4XUN1nWY5kWU+bNxLBEzAjsFKzahwfnhSDIiURpHUx2HTBCinrPH0XcTYiaV/PeJLqxdThF3oxMYxGDikjuJD0mOje9HQ4O/txRHv4qjzUI2V/QB6SoCta+JamHI8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708522087; c=relaxed/simple; bh=CnsEycGScQk42T2hhw/4OXRVlvNXdcJgM1o7lqYNl+g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=r8X9gLE9QLQVgMpSvjsmDjFbSSDEGk7Nh9Kdlu4ss/DsbhCz0GnzhTyngqvIjDbkSJR1tAlM6/DNZPlaUPWjEOlAhGBX8H3pwHgW6bjdaiVHCrOnbzZ5uT1hpzEL4HDT3SvgzwaTARJs24av8TtG4vkjiJcTuCqe89VDdb8H7n4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rqVBkXPj; 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="rqVBkXPj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DC34DC433F1; Wed, 21 Feb 2024 13:28:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708522087; bh=CnsEycGScQk42T2hhw/4OXRVlvNXdcJgM1o7lqYNl+g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rqVBkXPjtvIjoV49K7dUcrjmmbxYCnitiSCXPtMSGsknIVPOFmoe2q3vQ0tG21dFA hSHSYKlLZaUVGDffRaa18lp1gl+4lDHM92qLtN8wBBkax1ITWvotpwBzhgLEUt/CKq 82kgF9V+ikBbNJDZjvOA36lN+1sbtTY0CIYaG36k= 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 5.15 076/476] btrfs: avoid copying BTRFS_ROOT_SUBVOL_DEAD flag to snapshot of subvolume being deleted Date: Wed, 21 Feb 2024 14:02:07 +0100 Message-ID: <20240221130010.781987031@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240221130007.738356493@linuxfoundation.org> References: <20240221130007.738356493@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 5.15-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 @@ -4501,6 +4501,8 @@ int btrfs_delete_subvolume(struct inode 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 @@ -4512,25 +4514,25 @@ int btrfs_delete_subvolume(struct inode 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); /* @@ -4540,7 +4542,7 @@ int btrfs_delete_subvolume(struct inode */ 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)) { @@ -4606,15 +4608,17 @@ 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);