linux-kernel - [PATCH V2] bcachefs: Add checks for entry's

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Message-ID: <tencent_DB74336E9E1D1B304BFF1B3F25DBBAA6BB08@qq.com>
Date: Wed, 31 Jul 2024 09:35:56 +0800
From: Edward Adam Davis <eadavis@...com>
To: kent.overstreet@...ux.dev
Cc: eadavis@...com,
	linux-bcachefs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	syzbot+05d7520be047c9be86e0@...kaller.appspotmail.com,
	syzkaller-bugs@...glegroups.com
Subject: [PATCH V2] bcachefs: Add checks for entry's _data bytes

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@...kaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 fs/bcachefs/bcachefs_format.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
index e3b1bde489c3..d536da101e89 100644
--- a/fs/bcachefs/bcachefs_format.h
+++ b/fs/bcachefs/bcachefs_format.h
@@ -1252,6 +1252,11 @@ struct jset_entry_dev_usage {
 
 static inline unsigned jset_entry_dev_usage_nr_types(struct jset_entry_dev_usage *u)
 {
+	if (vstruct_bytes(&u->entry) < sizeof(struct jset_entry_dev_usage)) {
+		pr_info("entry data bytes %u is too small", vstruct_bytes(&u->entry));
+		return 0;
+	}
+
 	return (vstruct_bytes(&u->entry) - sizeof(struct jset_entry_dev_usage)) /
 		sizeof(struct jset_entry_dev_usage_type);
 }
-- 
2.43.0