linux-ext4 - [PATCH 2/2] ext4: Make sure to reset inode lockdep class when quota enabling fails

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Message-Id: <20211007155336.12493-3-jack@suse.cz>
Date:   Thu,  7 Oct 2021 17:53:36 +0200
From:   Jan Kara <jack@...e.cz>
To:     <linux-ext4@...r.kernel.org>
Cc:     Ted Tso <tytso@....edu>, Jan Kara <jack@...e.cz>,
        syzbot+3b6f9218b1301ddda3e2@...kaller.appspotmail.com
Subject: [PATCH 2/2] ext4: Make sure to reset inode lockdep class when quota enabling fails

When we succeed in enabling some quota type but fail to enable another
one with quota feature, we correctly disable all enabled quota types.
However we forget to reset i_data_sem lockdep class. When the inode gets
freed and reused, it will inherit this lockdep class (i_data_sem is
initialized only when a slab is created) and thus eventually lockdep
barfs about possible deadlocks.

Reported-and-tested-by: syzbot+3b6f9218b1301ddda3e2@...kaller.appspotmail.com
Signed-off-by: Jan Kara <jack@...e.cz>
---
 fs/ext4/super.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index fbe9cae63786..70b5fcbd351a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -6355,8 +6355,19 @@ int ext4_enable_quotas(struct super_block *sb)
 					"Failed to enable quota tracking "
 					"(type=%d, err=%d). Please run "
 					"e2fsck to fix.", type, err);
-				for (type--; type >= 0; type--)
+				for (type--; type >= 0; type--) {
+					struct inode *inode;
+
+					inode = sb_dqopt(sb)->files[type];
+					if (inode)
+						inode = igrab(inode);
 					dquot_quota_off(sb, type);
+					if (inode) {
+						lockdep_set_quota_inode(inode,
+							I_DATA_SEM_NORMAL);
+						iput(inode);
+					}
+				}
 
 				return err;
 			}
-- 
2.26.2