Re: [PATCH 6.1] ext4: fix access to uninitialised lock in fc replay path

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Jan 29, 2025 at 11:10:46AM +0100, vgiraud.opensource@witekio.com wrote:
> From: "Luis Henriques (SUSE)" <luis.henriques@linux.dev>
> 
> commit 23dfdb56581ad92a9967bcd720c8c23356af74c1 upstream.
> 
> The following kernel trace can be triggered with fstest generic/629 when
> executed against a filesystem with fast-commit feature enabled:
> 
> 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: 0 PID: 866 Comm: mount Not tainted 6.10.0+ #11
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-prebuilt.qemu.org 04/01/2014
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x66/0x90
>  register_lock_class+0x759/0x7d0
>  __lock_acquire+0x85/0x2630
>  ? __find_get_block+0xb4/0x380
>  lock_acquire+0xd1/0x2d0
>  ? __ext4_journal_get_write_access+0xd5/0x160
>  _raw_spin_lock+0x33/0x40
>  ? __ext4_journal_get_write_access+0xd5/0x160
>  __ext4_journal_get_write_access+0xd5/0x160
>  ext4_reserve_inode_write+0x61/0xb0
>  __ext4_mark_inode_dirty+0x79/0x270
>  ? ext4_ext_replay_set_iblocks+0x2f8/0x450
>  ext4_ext_replay_set_iblocks+0x330/0x450
>  ext4_fc_replay+0x14c8/0x1540
>  ? jread+0x88/0x2e0
>  ? rcu_is_watching+0x11/0x40
>  do_one_pass+0x447/0xd00
>  jbd2_journal_recover+0x139/0x1b0
>  jbd2_journal_load+0x96/0x390
>  ext4_load_and_init_journal+0x253/0xd40
>  ext4_fill_super+0x2cc6/0x3180
> ...
> 
> In the replay path there's an attempt to lock sbi->s_bdev_wb_lock in
> function ext4_check_bdev_write_error().  Unfortunately, at this point this
> spinlock has not been initialized yet.  Moving it's initialization to an
> earlier point in __ext4_fill_super() fixes this splat.
> 
> Signed-off-by: Luis Henriques (SUSE) <luis.henriques@linux.dev>
> Link: https://patch.msgid.link/20240718094356.7863-1-luis.henriques@linux.dev
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> Cc: stable@kernel.org
> Signed-off-by: Bruno VERNAY <bruno.vernay@se.com>
> Signed-off-by: Victor Giraud <vgiraud.opensource@witekio.com>
> ---
>  fs/ext4/super.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

You forgot about 6.6.y, please ALWAYS check if a commit is in a newer
kernel or not, because we can't take them if the are not there also.

thanks,

greg k-h