linux-kernel - Re: [syzbot] [gfs2?] KASAN: slab-use-after-free Read in gfs2_invalidate

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Date: Sun, 14 Apr 2024 09:48:17 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+3a36aeabd31497d63f6e@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [gfs2?] KASAN: slab-use-after-free Read in gfs2_invalidate_folio

please test uaf in gfs2_invalidate_folio

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git e8c39d0f57f3

diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index 192213c7359a..8d169b389dc1 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -202,16 +202,8 @@ void gfs2_trans_add_data(struct gfs2_glock *gl, struct buffer_head *bh)
 	}
 	gfs2_log_lock(sdp);
 	bd = bh->b_private;
-	if (bd == NULL) {
-		gfs2_log_unlock(sdp);
-		unlock_buffer(bh);
-		if (bh->b_private == NULL)
-			bd = gfs2_alloc_bufdata(gl, bh);
-		else
-			bd = bh->b_private;
-		lock_buffer(bh);
-		gfs2_log_lock(sdp);
-	}
+	if (bd == NULL)
+		bd = gfs2_alloc_bufdata(gl, bh);
 	gfs2_assert(sdp, bd->bd_gl == gl);
 	set_bit(TR_TOUCHED, &tr->tr_flags);
 	if (list_empty(&bd->bd_list)) {