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ext4: fix uninitialized ratelimit_state->lock access in __ext4_fill_super()

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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@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240102133730.1098120-1-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Baokun Li 2024-01-02 21:37:30 +08:00 committed by Theodore Ts'o
parent ea4fd933ab
commit b4b4fda34e
1 changed files with 10 additions and 12 deletions
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22
fs/ext4/super.c
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@ -5550,19 +5550,15 @@ 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 */
@ -5588,7 +5584,7 @@ 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))
@ -5605,15 +5601,17 @@ 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: