From: Kuniyuki Iwashima <kuniyu@amazon.com>
To: <john.fastabend@gmail.com>
Cc: <bpf@vger.kernel.org>, <edumazet@google.com>,
<jakub@cloudflare.com>, <martin.lau@kernel.org>,
<netdev@vger.kernel.org>, <kuniyu@amazon.com>
Subject: [PATCH bpf v2 1/2] bpf: syzkaller found null ptr deref in unix_bpf proto add
Date: Fri, 1 Dec 2023 13:14:53 -0800 [thread overview]
Message-ID: <20231201211453.27432-1-kuniyu@amazon.com> (raw)
In-Reply-To: <20231201180139.328529-2-john.fastabend@gmail.com>
From: John Fastabend <john.fastabend@gmail.com>
Date: Fri, 1 Dec 2023 10:01:38 -0800
> I added logic to track the sock pair for stream_unix sockets so that we
> ensure lifetime of the sock matches the time a sockmap could reference
> the sock (see fixes tag). I forgot though that we allow af_unix unconnected
> sockets into a sock{map|hash} map.
>
> This is problematic because previous fixed expected sk_pair() to exist
> and did not NULL check it. Because unconnected sockets have a NULL
> sk_pair this resulted in the NULL ptr dereference found by syzkaller.
>
> BUG: KASAN: null-ptr-deref in unix_stream_bpf_update_proto+0x72/0x430 net/unix/unix_bpf.c:171
> Write of size 4 at addr 0000000000000080 by task syz-executor360/5073
> Call Trace:
> <TASK>
> ...
> sock_hold include/net/sock.h:777 [inline]
> unix_stream_bpf_update_proto+0x72/0x430 net/unix/unix_bpf.c:171
> sock_map_init_proto net/core/sock_map.c:190 [inline]
> sock_map_link+0xb87/0x1100 net/core/sock_map.c:294
> sock_map_update_common+0xf6/0x870 net/core/sock_map.c:483
> sock_map_update_elem_sys+0x5b6/0x640 net/core/sock_map.c:577
> bpf_map_update_value+0x3af/0x820 kernel/bpf/syscall.c:167
>
> We considered just checking for the null ptr and skipping taking a ref
> on the NULL peer sock. But, if the socket is then connected() after
> being added to the sockmap we can cause the original issue again. So
> instead this patch blocks adding af_unix sockets that are not in the
> ESTABLISHED state.
I'm not sure if someone has the unconnected stream socket use case
though, can't we call additional sock_hold() in connect() by checking
sk_prot under sk_callback_lock ?
next prev parent reply other threads:[~2023-12-01 21:15 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-01 18:01 [PATCH bpf v2 0/2] bpf fix for unconnect af_unix socket John Fastabend
2023-12-01 18:01 ` [PATCH bpf v2 1/2] bpf: syzkaller found null ptr deref in unix_bpf proto add John Fastabend
2023-12-01 21:14 ` Kuniyuki Iwashima [this message]
2023-12-04 21:40 ` John Fastabend
2023-12-04 22:37 ` Kuniyuki Iwashima
2023-12-06 9:47 ` Jakub Sitnicki
2023-12-08 4:19 ` Cong Wang
2023-12-11 14:56 ` Daniel Borkmann
2023-12-13 23:23 ` [External] " Amery Hung
2023-12-01 18:01 ` [PATCH bpf v2 2/2] bpf: sockmap, test for unconnected af_unix sock John Fastabend
2023-12-12 10:09 ` [PATCH bpf v2 0/2] bpf fix for unconnect af_unix socket Jakub Sitnicki
2023-12-14 1:40 ` patchwork-bot+netdevbpf
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