linux-kernel - [PATCH next] gfs2: Add sanity check for sd

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Message-ID: <tencent_9C66663DC537949618361A4B5E750576B309@qq.com>
Date: Wed, 15 Oct 2025 17:51:04 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+6b156e132970e550194c@...kaller.appspotmail.com
Cc: agruenba@...hat.com,
	gfs2@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: [PATCH next] gfs2: Add sanity check for sd_jdesc

Asynchronous withdraw, when sd_withdraw_work is scheduled later than
put_super, will set sd_jdesc to NULL when clearing all journal index
information, triggering the syz report uaf.

Reported-by: syzbot+6b156e132970e550194c@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=6b156e132970e550194c
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 fs/gfs2/log.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 8312cd2cdae4..433a3a11a2f5 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -427,7 +427,8 @@ static void ail2_empty(struct gfs2_sbd *sdp, unsigned int new_tail)
  */
 
 bool gfs2_log_is_empty(struct gfs2_sbd *sdp) {
-	return atomic_read(&sdp->sd_log_blks_free) == sdp->sd_jdesc->jd_blocks;
+	return sdp->sd_jdesc &&
+	       atomic_read(&sdp->sd_log_blks_free) == sdp->sd_jdesc->jd_blocks;
 }
 
 static bool __gfs2_log_try_reserve_revokes(struct gfs2_sbd *sdp, unsigned int revokes)
-- 
2.43.0