Patch "ext4: avoid deadlock when expanding inode size" has been added to the 4.7-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    ext4: avoid deadlock when expanding inode size

to the 4.7-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ext4-avoid-deadlock-when-expanding-inode-size.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 2e81a4eeedcaa66e35f58b81e0755b87057ce392 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 11 Aug 2016 12:38:55 -0400
Subject: ext4: avoid deadlock when expanding inode size

From: Jan Kara <jack@suse.cz>

commit 2e81a4eeedcaa66e35f58b81e0755b87057ce392 upstream.

When we need to move xattrs into external xattr block, we call
ext4_xattr_block_set() from ext4_expand_extra_isize_ea(). That may end
up calling ext4_mark_inode_dirty() again which will recurse back into
the inode expansion code leading to deadlocks.

Protect from recursion using EXT4_STATE_NO_EXPAND inode flag and move
its management into ext4_expand_extra_isize_ea() since its manipulation
is safe there (due to xattr_sem) from possible races with
ext4_xattr_set_handle() which plays with it as well.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ext4/inode.c |    2 --
 fs/ext4/xattr.c |   19 +++++++++++++------
 2 files changed, 13 insertions(+), 8 deletions(-)

--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5460,8 +5460,6 @@ int ext4_mark_inode_dirty(handle_t *hand
 						      sbi->s_want_extra_isize,
 						      iloc, handle);
 			if (ret) {
-				ext4_set_inode_state(inode,
-						     EXT4_STATE_NO_EXPAND);
 				if (mnt_count !=
 					le16_to_cpu(sbi->s_es->s_mnt_count)) {
 					ext4_warning(inode->i_sb,
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1357,12 +1357,14 @@ int ext4_expand_extra_isize_ea(struct in
 	int isize_diff;	/* How much do we need to grow i_extra_isize */
 
 	down_write(&EXT4_I(inode)->xattr_sem);
+	/*
+	 * Set EXT4_STATE_NO_EXPAND to avoid recursion when marking inode dirty
+	 */
+	ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND);
 retry:
 	isize_diff = new_extra_isize - EXT4_I(inode)->i_extra_isize;
-	if (EXT4_I(inode)->i_extra_isize >= new_extra_isize) {
-		up_write(&EXT4_I(inode)->xattr_sem);
-		return 0;
-	}
+	if (EXT4_I(inode)->i_extra_isize >= new_extra_isize)
+		goto out;
 
 	header = IHDR(inode, raw_inode);
 	entry = IFIRST(header);
@@ -1391,8 +1393,7 @@ retry:
 				(void *)header, total_ino,
 				inode->i_sb->s_blocksize);
 		EXT4_I(inode)->i_extra_isize = new_extra_isize;
-		error = 0;
-		goto cleanup;
+		goto out;
 	}
 
 	/*
@@ -1552,6 +1553,8 @@ retry:
 		kfree(bs);
 	}
 	brelse(bh);
+out:
+	ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND);
 	up_write(&EXT4_I(inode)->xattr_sem);
 	return 0;
 
@@ -1563,6 +1566,10 @@ cleanup:
 	kfree(is);
 	kfree(bs);
 	brelse(bh);
+	/*
+	 * We deliberately leave EXT4_STATE_NO_EXPAND set here since inode
+	 * size expansion failed.
+	 */
 	up_write(&EXT4_I(inode)->xattr_sem);
 	return error;
 }


Patches currently in stable-queue which might be from jack@suse.cz are

queue-4.7/ext4-fix-xattr-shifting-when-expanding-inodes-part-2.patch
queue-4.7/ext4-fix-xattr-shifting-when-expanding-inodes.patch
queue-4.7/ext4-avoid-deadlock-when-expanding-inode-size.patch
queue-4.7/ext4-properly-align-shifted-xattrs-when-expanding-inodes.patch