In the following concurrency we will access the uninitialized rs->lock:
ext4_fill_super
ext4_register_sysfs
// sysfs registered msg_ratelimit_interval_ms
// Other processes modify rs->interval to
// non-zero via msg_ratelimit_interval_ms
ext4_orphan_cleanup
ext4_msg(sb, KERN_INFO, "Errors on filesystem, "
__ext4_msg
___ratelimit(&(EXT4_SB(sb)->s_msg_ratelimit_state)
if (!rs->interval) // do nothing if interval is 0
return 1;
raw_spin_trylock_irqsave(&rs->lock, flags)
raw_spin_trylock(lock)
_raw_spin_trylock
__raw_spin_trylock
spin_acquire(&lock->dep_map, 0, 1, _RET_IP_)
lock_acquire
__lock_acquire
register_lock_class
assign_lock_key
dump_stack();
ratelimit_state_init(&sbi->s_msg_ratelimit_state, 5 * HZ, 10);
raw_spin_lock_init(&rs->lock);
// init rs->lock here
and get the following dump_stack:
=========================================================
INFO: trying to register non-static key.
The code is fine but needs lockdep annotation, or maybe
you didn't initialize this object before use?
turning off the locking correctness validator.
CPU: 12 PID: 753 Comm: mount Tainted: G E 6.7.0-rc6-next-20231222 #504
[...]
Call Trace:
dump_stack_lvl+0xc5/0x170
dump_stack+0x18/0x30
register_lock_class+0x740/0x7c0
__lock_acquire+0x69/0x13a0
lock_acquire+0x120/0x450
_raw_spin_trylock+0x98/0xd0
___ratelimit+0xf6/0x220
__ext4_msg+0x7f/0x160 [ext4]
ext4_orphan_cleanup+0x665/0x740 [ext4]
__ext4_fill_super+0x21ea/0x2b10 [ext4]
ext4_fill_super+0x14d/0x360 [ext4]
[...]
=========================================================
Normally interval is 0 until s_msg_ratelimit_state is initialized, so
___ratelimit() does nothing. But registering sysfs precedes initializing
rs->lock, so it is possible to change rs->interval to a non-zero value
via the msg_ratelimit_interval_ms interface of sysfs while rs->lock is
uninitialized, and then a call to ext4_msg triggers the problem by
accessing an uninitialized rs->lock. Therefore register sysfs after all
initializations are complete to avoid such problems.
Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
---
fs/ext4/super.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 0980845c8b8f..1db23b0e8a4f 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5564,19 +5564,15 @@ static int __ext4_fill_super(struct
fs_context *fc, struct super_block *sb)
if (err)
goto failed_mount6;
- err = ext4_register_sysfs(sb);
- if (err)
- goto failed_mount7;
-
err = ext4_init_orphan_info(sb);
if (err)
- goto failed_mount8;
+ goto failed_mount7;
#ifdef CONFIG_QUOTA
/* Enable quota usage during mount. */
if (ext4_has_feature_quota(sb) && !sb_rdonly(sb)) {
err = ext4_enable_quotas(sb);
if (err)
- goto failed_mount9;
+ goto failed_mount8;
}
#endif /* CONFIG_QUOTA */
@@ -5602,7 +5598,7 @@ static int __ext4_fill_super(struct
fs_context *fc, struct super_block *sb)
ext4_msg(sb, KERN_INFO, "recovery complete");
err = ext4_mark_recovery_complete(sb, es);
if (err)
- goto failed_mount10;
+ goto failed_mount9;
}
if (test_opt(sb, DISCARD) &&
!bdev_max_discard_sectors(sb->s_bdev))
@@ -5619,15 +5615,17 @@ static int __ext4_fill_super(struct
fs_context *fc, struct super_block *sb)
atomic_set(&sbi->s_warning_count, 0);
atomic_set(&sbi->s_msg_count, 0);
+ /* Register sysfs after all initializations are complete. */
+ err = ext4_register_sysfs(sb);
+ if (err)
+ goto failed_mount9;
+
return 0;
-failed_mount10:
+failed_mount9:
ext4_quotas_off(sb, EXT4_MAXQUOTAS);
-failed_mount9: __maybe_unused
+failed_mount8: __maybe_unused
ext4_release_orphan_info(sb);
-failed_mount8:
- ext4_unregister_sysfs(sb);
- kobject_put(&sbi->s_kobj);
failed_mount7:
ext4_unregister_li_request(sb);
failed_mount6:
