Re: [PATCH 4.19 5.4 5.10 5.15 6.1 6.6] nilfs2: fix potential kernel bug due to lack of writeback flag waiting

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Jun 17, 2024 at 03:17:29AM +0900, Ryusuke Konishi wrote:
> commit a4ca369ca221bb7e06c725792ac107f0e48e82e7 upstream.
> 
> Destructive writes to a block device on which nilfs2 is mounted can cause
> a kernel bug in the folio/page writeback start routine or writeback end
> routine (__folio_start_writeback in the log below):
> 
>  kernel BUG at mm/page-writeback.c:3070!
>  Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
>  ...
>  RIP: 0010:__folio_start_writeback+0xbaa/0x10e0
>  Code: 25 ff 0f 00 00 0f 84 18 01 00 00 e8 40 ca c6 ff e9 17 f6 ff ff
>   e8 36 ca c6 ff 4c 89 f7 48 c7 c6 80 c0 12 84 e8 e7 b3 0f 00 90 <0f>
>   0b e8 1f ca c6 ff 4c 89 f7 48 c7 c6 a0 c6 12 84 e8 d0 b3 0f 00
>  ...
>  Call Trace:
>   <TASK>
>   nilfs_segctor_do_construct+0x4654/0x69d0 [nilfs2]
>   nilfs_segctor_construct+0x181/0x6b0 [nilfs2]
>   nilfs_segctor_thread+0x548/0x11c0 [nilfs2]
>   kthread+0x2f0/0x390
>   ret_from_fork+0x4b/0x80
>   ret_from_fork_asm+0x1a/0x30
>   </TASK>
> 
> This is because when the log writer starts a writeback for segment summary
> blocks or a super root block that use the backing device's page cache, it
> does not wait for the ongoing folio/page writeback, resulting in an
> inconsistent writeback state.
> 
> Fix this issue by waiting for ongoing writebacks when putting
> folios/pages on the backing device into writeback state.
> 
> Link: https://lkml.kernel.org/r/20240530141556.4411-1-konishi.ryusuke@gmail.com
> Fixes: 9ff05123e3bf ("nilfs2: segment constructor")
> Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
> Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> Please apply this patch to the stable trees indicated by the subject
> prefix instead of the patch that failed.
> 
> This patch is tailored to account for page/folio conversion and can
> be applied to v6.7 and earlier.
> 
> Also, all the builds and tests I did on each stable tree passed.

Now queued up, thanks.

greg k-h