Re: [PATCH] ocfs2: validate truncate log dinode before caching

[Joseph Qi]

On 7/22/26 5:11 PM, ZhengYuan Huang wrote:
> [BUG]
> A corrupted truncate log dinode can pass through mount initialization and
> reach the delayed flush worker, where it triggers:
> 
> kernel BUG at fs/ocfs2/alloc.c:6019!
> Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
> RIP: 0010:__ocfs2_flush_truncate_log+0xa87/0xf10 fs/ocfs2/alloc.c:6019
> Call Trace:
>  ocfs2_flush_truncate_log fs/ocfs2/alloc.c:6084 [inline]
>  ocfs2_truncate_log_worker+0xa9/0x180 fs/ocfs2/alloc.c:6097
>  process_one_work+0x8e0/0x1980 kernel/workqueue.c:3263
>  ...
> 

I've encountered this BUG occasionality. But I don't see why it happens.
Do you have more clues on how to reproduce it?

Thanks,
Joseph

> [CAUSE]
> ocfs2_get_truncate_log_info() assumes that ocfs2_read_inode_block()
> always validates the returned dinode. However, ocfs2_read_blocks() skips
> the validation callback for JBD-managed buffers. The function then reads
> truncate log fields and exposes the invalid buffer to callers, allowing
> ocfs2_truncate_log_init() to retain it in osb->osb_tl_bh.
> 
> [FIX]
> Check the dinode signature in ocfs2_get_truncate_log_info() immediately
> after the inode read. Reject an invalid dinode as filesystem corruption
> before reading truncate log fields or returning the inode and buffer to
> the caller. This keeps invalid state out of the long-lived truncate log
> cache and preserves the validated-buffer invariant in append, flush, and
> recovery paths.
> 
> Fixes: 10995aa2451a ("ocfs2: Morph the haphazard OCFS2_IS_VALID_DINODE() checks.")
> Assisted-by: Codex:gpt-5.6-sol
> Signed-off-by: ZhengYuan Huang <gality369@xxxxxxxxx>
> ---
>  fs/ocfs2/alloc.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
> index be09e766ac1f..e36ae2e522d3 100644
> --- a/fs/ocfs2/alloc.c
> +++ b/fs/ocfs2/alloc.c
> @@ -6192,6 +6192,19 @@ static int ocfs2_get_truncate_log_info(struct ocfs2_super *osb,
>  	}
>  
>  	di = (struct ocfs2_dinode *)bh->b_data;
> +	/*
> +	 * A JBD-managed buffer may skip the read validation callback. Check
> +	 * the signature before exposing the truncate log to callers.
> +	 */
> +	if (!OCFS2_IS_VALID_DINODE(di)) {
> +		status = ocfs2_error(osb->sb,
> +				     "Invalid truncate log dinode #%llu\n",
> +				     (unsigned long long)bh->b_blocknr);
> +		iput(inode);
> +		brelse(bh);
> +		goto bail;
> +	}
> +
>  	tl = &di->id2.i_dealloc;
>  	tl_count = le16_to_cpu(tl->tl_count);
>  	tl_used = le16_to_cpu(tl->tl_used);