Re: [PATCH net] net/sched: em_canid: add length check before reading CAN ID
From: Eric Dumazet <edumazet@google.com>
Date: 2025-11-26 04:16:37
Also in:
linux-can, linux-kernel-mentees, lkml
On Tue, Nov 25, 2025 at 7:46 PM [off-list ref] wrote:
quoted hunk ↗ jump to hunk
From: Shaurya Rane <redacted> Add a check to verify that the skb has at least sizeof(canid_t) bytes before reading the CAN ID from skb->data. This prevents reading uninitialized memory when processing malformed packets that don't contain a valid CAN frame. Reported-by: syzbot+5d8269a1e099279152bc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=5d8269a1e099279152bc Fixes: f057bbb6f9ed ("net: em_canid: Ematch rule to match CAN frames according to their identifiers") Signed-off-by: Shaurya Rane <redacted> --- net/sched/em_canid.c | 3 +++ 1 file changed, 3 insertions(+)diff --git a/net/sched/em_canid.c b/net/sched/em_canid.c index 5337bc462755..a9b6cab70ff1 100644 --- a/net/sched/em_canid.c +++ b/net/sched/em_canid.c@@ -99,6 +99,9 @@ static int em_canid_match(struct sk_buff *skb, struct tcf_ematch *m, int i; const struct can_filter *lp; + if (skb->len < sizeof(canid_t)) + return 0; +
Please keep in mind that this test is not enough, even if it may prevent a particular syzbot repro from triggering a bug. Take a look at pskb_may_pull() for details.