Re: [syzbot] [gfs2?] KASAN: slab-use-after-free Read in gfs2_invalidate_folio

[Edward Adam Davis]

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/aops.c b/fs/gfs2/aops.c
index 974aca9c8ea8..4ae5e73b6992 100644
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -613,6 +613,7 @@ static void gfs2_discard(struct gfs2_sbd *sdp, struct buffer_head *bh)
 	gfs2_log_lock(sdp);
 	clear_buffer_dirty(bh);
 	bd = bh->b_private;
+	printk("bh: %p, bd: %p, %s\n", bh, bd, __func__);
 	if (bd) {
 		if (!list_empty(&bd->bd_list) && !buffer_pinned(bh))
 			list_del_init(&bd->bd_list);
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 8cddf955ebc0..d05decef6af5 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -1007,6 +1007,7 @@ static void trans_drain(struct gfs2_trans *tr)
 {
 	struct gfs2_bufdata *bd;
 	struct list_head *head;
+	struct buffer_head *bh;
 
 	if (!tr)
 		return;
@@ -1022,6 +1023,9 @@ static void trans_drain(struct gfs2_trans *tr)
 	head = &tr->tr_databuf;
 	while (!list_empty(head)) {
 		bd = list_first_entry(head, struct gfs2_bufdata, bd_list);
+		bh = container_of((void *)bd, struct buffer_head, b_private);
+		printk("bh: %p, bd: %p, %s\n", bh, bd, __func__);
+		bh->b_private = NULL;
 		list_del_init(&bd->bd_list);
 		if (!list_empty(&bd->bd_ail_st_list))
 			gfs2_remove_from_ail(bd);