[PATCH] bcachefs: Add checks for entry's _data bytes

[Edward Adam Davis]

syzbot report slab-out-of-bounds in journal_entry_dev_usage_to_text,
it because vstruct_bytes(entry) smaller than sizeof(struct 
jset_entry_dev_usage), overflow occurs when calculating the difference in
jset_entry_dev_usage_nr_types(u).

Reported-by: syzbot+05d7520be047c9be86e0@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=05d7520be047c9be86e0
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
 fs/bcachefs/sb-clean.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/bcachefs/sb-clean.c b/fs/bcachefs/sb-clean.c
index 47f10ab57f40..278e1a25159a 100644
--- a/fs/bcachefs/sb-clean.c
+++ b/fs/bcachefs/sb-clean.c
@@ -310,6 +310,9 @@ static void bch2_sb_clean_to_text(struct printbuf *out, struct bch_sb *sb,
 		    !entry->u64s)
 			continue;
 
+		if (vstruct_bytes(entry) < sizeof(struct jset_entry_dev_usage))
+			continue;
+
 		bch2_journal_entry_to_text(out, NULL, entry);
 		prt_newline(out);
 	}
-- 
2.43.0