linux-ext4 - Re: [4.7-rc6 ext3 BUG] kernel BUG at fs/ext4/xattr.c:1331

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Message-ID: <20160801030909.GD12853@thunk.org>
Date:	Sun, 31 Jul 2016 23:09:09 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	Dave Chinner <david@...morbit.com>,
	Eric Sandeen <sandeen@...hat.com>, linux-ext4@...r.kernel.org
Subject: Re: [4.7-rc6 ext3 BUG] kernel BUG at fs/ext4/xattr.c:1331

On Fri, Jul 29, 2016 at 08:42:10AM +0200, Jan Kara wrote:
> 
> I have written some fixes, working on testing them... So hopefully I can
> submit them later today or next week.

How complicated are the fixes?  This should work as a temporary
workaround and it going to be very simple to backport.

	       	  	      	   	  - Ted
					  

commit e92d5b1cf6af642bc5018562e58044fd771f82bf
Author: Theodore Ts'o <tytso@....edu>
Date:   Sun Jul 31 23:08:28 2016 -0400

    ext4: suppress inode growth for file systems w/o project quota
    
    We have not added a new "extra" inode field in a very long time, and
    the code to deal with moving the extended attributes down to make room
    for the extra inode fields has bitrotted and can cause kernel BUGS.
    
    Very few people will likely use project quotas (and those that do will
    likely be creating a new file system from scratch) so as a temporary
    pallative until we are sure the inode expansion code is all sane,
    let's not try to expand the inode "extra" fields if the project
    feature has not been enabled.
    
    Cc: stable@...r.kernel.org # v4.4+
    Signed-off-by: Theodore Ts'o <tytso@....edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c13a4e4..e2622ba 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3968,6 +3968,17 @@ no_journal:
 	if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE) {
 		sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
 						     EXT4_GOOD_OLD_INODE_SIZE;
+		/*
+		 * This is a temporary hack; we have not added a new
+		 * "extra" inode field in a long time, and the code to
+		 * expand the inode structure has bitrotted and can
+		 * cause kernel BUG's.  If the file system does not
+		 * have the project feature, let's not try to expand
+		 * the inode's extra size as a temporary pallitive
+		 * until we can fix up the inode expansion code.
+		 */
+		if (!ext4_has_feature_project(sb))
+			sbi->s_want_extra_isize -= sizeof(__le32);
 		if (ext4_has_feature_extra_isize(sb)) {
 			if (sbi->s_want_extra_isize <
 			    le16_to_cpu(es->s_want_extra_isize))
--
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