From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Mon, 9 May 2022 14:42:31 +0000 (+0200)
Subject: 4.19-stable patches
X-Git-Tag: v4.9.313~48
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c834378d4be75693f8e0217f404ff3d7e89010b7;p=thirdparty%2Fkernel%2Fstable-queue.git

4.19-stable patches

added patches:
	btrfs-always-log-symlinks-in-full-mode.patch
---

diff --git a/queue-4.19/btrfs-always-log-symlinks-in-full-mode.patch b/queue-4.19/btrfs-always-log-symlinks-in-full-mode.patch
new file mode 100644
index 00000000000..47694226e1d
--- /dev/null
+++ b/queue-4.19/btrfs-always-log-symlinks-in-full-mode.patch
@@ -0,0 +1,89 @@
+From d0e64a981fd841cb0f28fcd6afcac55e6f1e6994 Mon Sep 17 00:00:00 2001
+From: Filipe Manana <fdmanana@suse.com>
+Date: Thu, 21 Apr 2022 10:56:39 +0100
+Subject: btrfs: always log symlinks in full mode
+
+From: Filipe Manana <fdmanana@suse.com>
+
+commit d0e64a981fd841cb0f28fcd6afcac55e6f1e6994 upstream.
+
+On Linux, empty symlinks are invalid, and attempting to create one with
+the system call symlink(2) results in an -ENOENT error and this is
+explicitly documented in the man page.
+
+If we rename a symlink that was created in the current transaction and its
+parent directory was logged before, we actually end up logging the symlink
+without logging its content, which is stored in an inline extent. That
+means that after a power failure we can end up with an empty symlink,
+having no content and an i_size of 0 bytes.
+
+It can be easily reproduced like this:
+
+  $ mkfs.btrfs -f /dev/sdc
+  $ mount /dev/sdc /mnt
+
+  $ mkdir /mnt/testdir
+  $ sync
+
+  # Create a file inside the directory and fsync the directory.
+  $ touch /mnt/testdir/foo
+  $ xfs_io -c "fsync" /mnt/testdir
+
+  # Create a symlink inside the directory and then rename the symlink.
+  $ ln -s /mnt/testdir/foo /mnt/testdir/bar
+  $ mv /mnt/testdir/bar /mnt/testdir/baz
+
+  # Now fsync again the directory, this persist the log tree.
+  $ xfs_io -c "fsync" /mnt/testdir
+
+  <power failure>
+
+  $ mount /dev/sdc /mnt
+  $ stat -c %s /mnt/testdir/baz
+  0
+  $ readlink /mnt/testdir/baz
+  $
+
+Fix this by always logging symlinks in full mode (LOG_INODE_ALL), so that
+their content is also logged.
+
+A test case for fstests will follow.
+
+CC: stable@vger.kernel.org # 4.9+
+Signed-off-by: Filipe Manana <fdmanana@suse.com>
+Signed-off-by: David Sterba <dsterba@suse.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ fs/btrfs/tree-log.c |   14 +++++++++++++-
+ 1 file changed, 13 insertions(+), 1 deletion(-)
+
+--- a/fs/btrfs/tree-log.c
++++ b/fs/btrfs/tree-log.c
+@@ -4907,6 +4907,18 @@ static int btrfs_log_inode(struct btrfs_
+ 	}
+ 
+ 	/*
++	 * For symlinks, we must always log their content, which is stored in an
++	 * inline extent, otherwise we could end up with an empty symlink after
++	 * log replay, which is invalid on linux (symlink(2) returns -ENOENT if
++	 * one attempts to create an empty symlink).
++	 * We don't need to worry about flushing delalloc, because when we create
++	 * the inline extent when the symlink is created (we never have delalloc
++	 * for symlinks).
++	 */
++	if (S_ISLNK(inode->vfs_inode.i_mode))
++		inode_only = LOG_INODE_ALL;
++
++	/*
+ 	 * a brute force approach to making sure we get the most uptodate
+ 	 * copies of everything.
+ 	 */
+@@ -5462,7 +5474,7 @@ process_leaf:
+ 			}
+ 
+ 			ctx->log_new_dentries = false;
+-			if (type == BTRFS_FT_DIR || type == BTRFS_FT_SYMLINK)
++			if (type == BTRFS_FT_DIR)
+ 				log_mode = LOG_INODE_ALL;
+ 			ret = btrfs_log_inode(trans, root, BTRFS_I(di_inode),
+ 					      log_mode, 0, LLONG_MAX, ctx);
diff --git a/queue-4.19/series b/queue-4.19/series
index 3a7a6d3b023..dcee50b4c1c 100644
--- a/queue-4.19/series
+++ b/queue-4.19/series
@@ -76,3 +76,4 @@ net-stmmac-dwmac-sun8i-add-missing-of_node_put-in-sun8i_dwmac_register_mdio_mux.
 net-emaclite-add-error-handling-for-of_address_to_resource.patch
 selftests-mirror_gre_bridge_1q-avoid-changing-pvid-while-interface-is-operational.patch
 smsc911x-allow-using-irq0.patch
+btrfs-always-log-symlinks-in-full-mode.patch