Messages in this thread | | | Subject | Re: [PATCH net] bpf: test_run: fix WARNING in format_decode | From | Daniel Borkmann <> | Date | Mon, 27 Nov 2023 15:10:52 +0100 |
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On 11/22/23 6:28 AM, Yonghong Song wrote: > On 11/21/23 7:50 PM, Edward Adam Davis wrote: >> Confirm that skb->len is not 0 to ensure that skb length is valid. >> >> Fixes: 114039b34201 ("bpf: Move skb->len == 0 checks into __bpf_redirect") >> Reported-by: syzbot+e2c932aec5c8a6e1d31c@syzkaller.appspotmail.com >> Signed-off-by: Edward Adam Davis <eadavis@qq.com> > > Stan, Could you take a look at this patch?
I think this only papers over the bug.. also BPF selftests seem to break with this change.
Looking again at the syzkaller trace :
[...] Please remove unsupported %\0 in format string WARNING: CPU: 0 PID: 5068 at lib/vsprintf.c:2675 format_decode+0xa03/0xba0 lib/vsprintf.c:2675 [...]
We need to fix bpf_bprintf_prepare() instead to reject invalid fmts such as %0 and similar.
>> net/bpf/test_run.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c >> index c9fdcc5cdce1..78258a822a5c 100644 >> --- a/net/bpf/test_run.c >> +++ b/net/bpf/test_run.c >> @@ -845,6 +845,9 @@ static int convert___skb_to_skb(struct sk_buff *skb, struct __sk_buff *__skb) >> { >> struct qdisc_skb_cb *cb = (struct qdisc_skb_cb *)skb->cb; >> + if (!skb->len) >> + return -EINVAL; >> + >> if (!__skb) >> return 0;
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