linux-ext4 - [PATCH 4/4] ext4: add lockdep annotations for i_data_sem for ea

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Date:   Tue, 23 May 2023 23:49:51 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc:     "Theodore Ts'o" <tytso@....edu>, stable@...nel.org,
        syzbot+298c5d8fb4a128bc27b0@...kaller.appspotmail.com
Subject: [PATCH 4/4] ext4: add lockdep annotations for i_data_sem for ea_inode's

Treat i_data_sem for ea_inodes as being in their own lockdep class to
avoid lockdep complaints about ext4_setattr's use of inode_lock() on
normal inodes potentially causing lock ordering with i_data_sem on
ea_inodes in ext4_xattr_inode_write().  However, ea_inodes will be
operated on by ext4_setattr(), so this isn't a problem.

Cc: stable@...nel.org
Link: https://syzkaller.appspot.com/bug?extid=298c5d8fb4a128bc27b0
Reported-by: syzbot+298c5d8fb4a128bc27b0@...kaller.appspotmail.com
Signed-off-by: Theodore Ts'o <tytso@....edu>
---
 fs/ext4/ext4.h  | 2 ++
 fs/ext4/xattr.c | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 9525c52b78dc..8104a21b001a 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -918,11 +918,13 @@ do {									       \
  *			  where the second inode has larger inode number
  *			  than the first
  *  I_DATA_SEM_QUOTA  - Used for quota inodes only
+ *  I_DATA_SEM_EA     - Used for ea_inodes only
  */
 enum {
 	I_DATA_SEM_NORMAL = 0,
 	I_DATA_SEM_OTHER,
 	I_DATA_SEM_QUOTA,
+	I_DATA_SEM_EA
 };
 
 
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index ff7ab63c5b4f..13d7f17a9c8c 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -121,7 +121,11 @@ ext4_expand_inode_array(struct ext4_xattr_inode_array **ea_inode_array,
 #ifdef CONFIG_LOCKDEP
 void ext4_xattr_inode_set_class(struct inode *ea_inode)
 {
+	struct ext4_inode_info *ei = EXT4_I(ea_inode);
+
 	lockdep_set_subclass(&ea_inode->i_rwsem, 1);
+	(void) ei;	/* shut up clang warning if !CONFIG_LOCKDEP */
+	lockdep_set_subclass(&ei->i_data_sem, I_DATA_SEM_EA);
 }
 #endif
 
-- 
2.31.0