linux-kernel - Re: [BUG] xfs: NULL pointer dereference in xfs_buf.h: xfs_buf

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Message-ID: <aR1eeeCKE4AJSKwL@infradead.org>
Date: Tue, 18 Nov 2025 22:06:49 -0800
From: Christoph Hellwig <hch@...radead.org>
To: 李天宇 <lty218@....pku.edu.cn>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
	linux-xfs <linux-xfs@...r.kernel.org>, cem <cem@...nel.org>
Subject: Re: [BUG] xfs: NULL pointer dereference in xfs_buf.h: xfs_buf_daddr()

On Tue, Nov 18, 2025 at 07:06:14PM +0800, 李天宇 wrote:
> The kernel reports a kernel NULL pointer dereference when the sys_mount is called. This is triggered by the statement b_maps[0], where b_maps is NULL.
> 
> This bug was discovered through a fuzzing framework on Linux v6.2

Linux 6.2 is ancient (Feb 2023), and the buffer cache code has seen a
major rewrite since:

ch@...ck:~/work/linux$ git diff v6.2..HEAD fs/xfs/xfs_buf.[ch] | diffstat
 xfs_buf.c | 1651 +++++++++++++++++++++++++++++++++++++++-----------------------------------------------------
  xfs_buf.h |   96 +++--
2 files changed, 768 insertions(+), 979 deletions(-)

hch@...ck:~/work/linux$ wc -l fs/xfs/xfs_buf.[ch]
 2132 fs/xfs/xfs_buf.c
  391 fs/xfs/xfs_buf.h
 2523 total

so I'm not sure how relevant this report is, especially without a good
report.