From: Paolo Abeni pabeni@redhat.com
[ Upstream commit adf7341064982de923a1f8a11bcdec48be6b3004 ]
Nicolas reported the following oops:
[ 1521.392541] BUG: kernel NULL pointer dereference, address: 00000000000000c0 [ 1521.394189] #PF: supervisor read access in kernel mode [ 1521.395376] #PF: error_code(0x0000) - not-present page [ 1521.396607] PGD 0 P4D 0 [ 1521.397156] Oops: 0000 [#1] SMP PTI [ 1521.398020] CPU: 0 PID: 22986 Comm: kworker/0:2 Not tainted 5.8.0-rc4+ #109 [ 1521.399618] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 [ 1521.401728] Workqueue: events mptcp_worker [ 1521.402651] RIP: 0010:mptcp_subflow_create_socket+0xf1/0x1c0 [ 1521.403954] Code: 24 08 89 44 24 04 48 8b 7a 18 e8 2a 48 d4 ff 8b 44 24 04 85 c0 75 7a 48 8b 8b 78 02 00 00 48 8b 54 24 08 48 8d bb 80 00 00 00 <48> 8b 89 c0 00 00 00 48 89 8a c0 00 00 00 48 8b 8b 78 02 00 00 8b [ 1521.408201] RSP: 0000:ffffabc4002d3c60 EFLAGS: 00010246 [ 1521.409433] RAX: 0000000000000000 RBX: ffffa0b9ad8c9a00 RCX: 0000000000000000 [ 1521.411096] RDX: ffffa0b9ae78a300 RSI: 00000000fffffe01 RDI: ffffa0b9ad8c9a80 [ 1521.412734] RBP: ffffa0b9adff2e80 R08: ffffa0b9af02d640 R09: ffffa0b9ad923a00 [ 1521.414333] R10: ffffabc4007139f8 R11: fefefefefefefeff R12: ffffabc4002d3cb0 [ 1521.415918] R13: ffffa0b9ad91fa58 R14: ffffa0b9ad8c9f9c R15: 0000000000000000 [ 1521.417592] FS: 0000000000000000(0000) GS:ffffa0b9af000000(0000) knlGS:0000000000000000 [ 1521.419490] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1521.420839] CR2: 00000000000000c0 CR3: 000000002951e006 CR4: 0000000000160ef0 [ 1521.422511] Call Trace: [ 1521.423103] __mptcp_subflow_connect+0x94/0x1f0 [ 1521.425376] mptcp_pm_create_subflow_or_signal_addr+0x200/0x2a0 [ 1521.426736] mptcp_worker+0x31b/0x390 [ 1521.431324] process_one_work+0x1fc/0x3f0 [ 1521.432268] worker_thread+0x2d/0x3b0 [ 1521.434197] kthread+0x117/0x130 [ 1521.435783] ret_from_fork+0x22/0x30
on some unconventional configuration.
The MPTCP protocol is trying to create a subflow for an unaccepted server socket. That is allowed by the RFC, even if subflow creation will likely fail. Unaccepted sockets have still a NULL sk_socket field, avoid the issue by failing earlier.
Reported-and-tested-by: Nicolas Rybowski nicolas.rybowski@tessares.net Fixes: 7d14b0d2b9b3 ("mptcp: set correct vfs info for subflows") Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Matthieu Baerts matthieu.baerts@tessares.net Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/subflow.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -999,6 +999,12 @@ int mptcp_subflow_create_socket(struct s struct socket *sf; int err;
+ /* un-accepted server sockets can reach here - on bad configuration + * bail early to avoid greater trouble later + */ + if (unlikely(!sk->sk_socket)) + return -EINVAL; + err = sock_create_kern(net, sk->sk_family, SOCK_STREAM, IPPROTO_TCP, &sf); if (err)