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Message-ID: <20200411004320.py2cashe4edsjdzp@shells.gnugeneration.com>
Date: Fri, 10 Apr 2020 17:43:20 -0700
From: Vito Caputo <vcaputo@...garu.com>
To: netdev@...r.kernel.org
Cc: courmisch@...il.com, davem@...emloft.net, kuba@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: kernel BUG at net/phonet/socket.c:LINE!
Hello peeps,
I stared a bit at the code surrounding this report, and maybe someone more
familiar with the network stack can clear something up for me real quick:
> RIP: 0010:pn_socket_autobind net/phonet/socket.c:213 [inline]
net/phonet/socket.c:
202 static int pn_socket_autobind(struct socket *sock)
203 {
204 struct sockaddr_pn sa;
205 int err;
206
207 memset(&sa, 0, sizeof(sa));
208 sa.spn_family = AF_PHONET;
209 err = pn_socket_bind(sock, (struct sockaddr *)&sa,
210 sizeof(struct sockaddr_pn));
211 if (err != -EINVAL)
212 return err;
213 BUG_ON(!pn_port(pn_sk(sock->sk)->sobject));
214 return 0; /* socket was already bound */
215 }
line 213 is the BUG_ON for !sock->sk->sobject, a phonet-specific member:
include/net/phonet/phonet.h:
23 struct pn_sock {
24 struct sock sk;
25 u16 sobject;
26 u16 dobject;
27 u8 resource;
28 };
pn_socket_autobind() expects that to be non-null whenever pn_socket_bind()
returns -EINVAL, which seems odd, but the comment claims it's already bound,
let's look at pn_socket_bind():
net/phonet/socket.c:
156 static int pn_socket_bind(struct socket *sock, struct sockaddr *addr, int len)
157 {
158 struct sock *sk = sock->sk;
159 struct pn_sock *pn = pn_sk(sk);
160 struct sockaddr_pn *spn = (struct sockaddr_pn *)addr;
161 int err;
162 u16 handle;
163 u8 saddr;
164
165 if (sk->sk_prot->bind)
166 return sk->sk_prot->bind(sk, addr, len);
167
168 if (len < sizeof(struct sockaddr_pn))
169 return -EINVAL;
170 if (spn->spn_family != AF_PHONET)
171 return -EAFNOSUPPORT;
172
173 handle = pn_sockaddr_get_object((struct sockaddr_pn *)addr);
174 saddr = pn_addr(handle);
175 if (saddr && phonet_address_lookup(sock_net(sk), saddr))
176 return -EADDRNOTAVAIL;
177
178 lock_sock(sk);
179 if (sk->sk_state != TCP_CLOSE || pn_port(pn->sobject)) {
180 err = -EINVAL; /* attempt to rebind */
181 goto out;
182 }
183 WARN_ON(sk_hashed(sk));
184 mutex_lock(&port_mutex);
185 err = sk->sk_prot->get_port(sk, pn_port(handle));
186 if (err)
187 goto out_port;
188
189 /* get_port() sets the port, bind() sets the address if applicable */
190 pn->sobject = pn_object(saddr, pn_port(pn->sobject));
191 pn->resource = spn->spn_resource;
192
193 /* Enable RX on the socket */
194 err = sk->sk_prot->hash(sk);
195 out_port:
196 mutex_unlock(&port_mutex);
197 out:
198 release_sock(sk);
199 return err;
200 }
The first return branch in there simply hands off the bind to and indirection
sk->sk_prot->bind() if present. This smells ripe for breaking the assumptions
of that BUG_ON(). I'm assuming there's no point for such an indirection if not
to enable a potentially non-phonet-ops hook, otherwise we'd just be do the
bind. If not, isn't this plain recursive? Color me confused. Will other
bind() implementations return -EINVAL when already bound with sobject set? no.
Furthermore, -EINVAL is also returned when len < sizeof(struct sockaddr_pn),
maybe the rebind case should return -EADDRINUSE instead of -EINVAL?
I must be missing some things.
Regards,
Vito Caputo
On Fri, Apr 10, 2020 at 12:16:17AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: b93cfb9c net: icmp6: do not select saddr from iif when rou..
> git tree: net
> console output: https://syzkaller.appspot.com/x/log.txt?x=13501d2be00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=94a7f1dec460ee83
> dashboard link: https://syzkaller.appspot.com/bug?extid=2dc91e7fc3dea88b1e8a
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+2dc91e7fc3dea88b1e8a@...kaller.appspotmail.com
>
> ------------[ cut here ]------------
> kernel BUG at net/phonet/socket.c:213!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 0 PID: 8394 Comm: syz-executor.4 Not tainted 5.6.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:pn_socket_autobind net/phonet/socket.c:213 [inline]
> RIP: 0010:pn_socket_autobind+0x13c/0x160 net/phonet/socket.c:202
> Code: 44 05 00 00 00 00 00 44 89 e0 48 8b 4c 24 58 65 48 33 0c 25 28 00 00 00 75 23 48 83 c4 60 5b 5d 41 5c 41 5d c3 e8 b4 ad 41 fa <0f> 0b e8 9d 56 7f fa eb 9f e8 b6 56 7f fa e9 6d ff ff ff e8 0c dd
> RSP: 0018:ffffc900034cfda8 EFLAGS: 00010212
> RAX: 0000000000040000 RBX: 0000000000000000 RCX: ffffc90011d66000
> RDX: 0000000000000081 RSI: ffffffff873183dc RDI: 0000000000000003
> RBP: 1ffff92000699fb5 R08: ffff8880620f61c0 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
> FS: 00007f84223c9700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000004d8730 CR3: 000000005cce0000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> pn_socket_listen+0x40/0x200 net/phonet/socket.c:399
> __sys_listen+0x17d/0x250 net/socket.c:1696
> __do_sys_listen net/socket.c:1705 [inline]
> __se_sys_listen net/socket.c:1703 [inline]
> __x64_sys_listen+0x50/0x70 net/socket.c:1703
> do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
> entry_SYSCALL_64_after_hwframe+0x49/0xb3
> RIP: 0033:0x45c889
> Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f84223c8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000032
> RAX: ffffffffffffffda RBX: 00007f84223c96d4 RCX: 000000000045c889
> RDX: 0000000000000000 RSI: 000000000000007d RDI: 0000000000000003
> RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 0000000000000712 R14: 00000000004c9e2d R15: 000000000076bf0c
> Modules linked in:
> ---[ end trace 65d6f1331216c544 ]---
> RIP: 0010:pn_socket_autobind net/phonet/socket.c:213 [inline]
> RIP: 0010:pn_socket_autobind+0x13c/0x160 net/phonet/socket.c:202
> Code: 44 05 00 00 00 00 00 44 89 e0 48 8b 4c 24 58 65 48 33 0c 25 28 00 00 00 75 23 48 83 c4 60 5b 5d 41 5c 41 5d c3 e8 b4 ad 41 fa <0f> 0b e8 9d 56 7f fa eb 9f e8 b6 56 7f fa e9 6d ff ff ff e8 0c dd
> RSP: 0018:ffffc900034cfda8 EFLAGS: 00010212
> RAX: 0000000000040000 RBX: 0000000000000000 RCX: ffffc90011d66000
> RDX: 0000000000000081 RSI: ffffffff873183dc RDI: 0000000000000003
> RBP: 1ffff92000699fb5 R08: ffff8880620f61c0 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
> FS: 00007f84223c9700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000076c000 CR3: 000000005cce0000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
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