From: Eric Dumazet edumazet@google.com
commit 032be5f19a94de51093851757089133dcc1e92aa upstream.
After commit 5271953cad31 ("rxrpc: Use the UDP encap_rcv hook"), rxrpc_input_packet() is directly called from lockless UDP receive path, under rcu_read_lock() protection.
It must therefore use RCU rules :
- udp_sk->sk_user_data can be cleared at any point in this function. rcu_dereference_sk_user_data() is what we need here.
- Also, since sk_user_data might have been set in rxrpc_open_socket() we must observe a proper RCU grace period before kfree(local) in rxrpc_lookup_local()
v4: @local can be NULL in xrpc_lookup_local() as reported by kbuild test robot lkp@intel.com and Julia Lawall julia.lawall@lip6.fr, thanks !
v3,v2 : addressed David Howells feedback, thanks !
syzbot reported :
kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 19236 Comm: syz-executor703 Not tainted 5.1.0-rc6 #79 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__lock_acquire+0xbef/0x3fb0 kernel/locking/lockdep.c:3573 Code: 00 0f 85 a5 1f 00 00 48 81 c4 10 01 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 4a 21 00 00 49 81 7d 00 20 54 9c 89 0f 84 cf f4 RSP: 0018:ffff88809d7aef58 EFLAGS: 00010002 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000026 RSI: 0000000000000000 RDI: 0000000000000001 RBP: ffff88809d7af090 R08: 0000000000000001 R09: 0000000000000001 R10: ffffed1015d05bc7 R11: ffff888089428600 R12: 0000000000000000 R13: 0000000000000130 R14: 0000000000000001 R15: 0000000000000001 FS: 00007f059044d700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004b6040 CR3: 00000000955ca000 CR4: 00000000001406f0 Call Trace: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152 skb_queue_tail+0x26/0x150 net/core/skbuff.c:2972 rxrpc_reject_packet net/rxrpc/input.c:1126 [inline] rxrpc_input_packet+0x4a0/0x5536 net/rxrpc/input.c:1414 udp_queue_rcv_one_skb+0xaf2/0x1780 net/ipv4/udp.c:2011 udp_queue_rcv_skb+0x128/0x730 net/ipv4/udp.c:2085 udp_unicast_rcv_skb.isra.0+0xb9/0x360 net/ipv4/udp.c:2245 __udp4_lib_rcv+0x701/0x2ca0 net/ipv4/udp.c:2301 udp_rcv+0x22/0x30 net/ipv4/udp.c:2482 ip_protocol_deliver_rcu+0x60/0x8f0 net/ipv4/ip_input.c:208 ip_local_deliver_finish+0x23b/0x390 net/ipv4/ip_input.c:234 NF_HOOK include/linux/netfilter.h:289 [inline] NF_HOOK include/linux/netfilter.h:283 [inline] ip_local_deliver+0x1e9/0x520 net/ipv4/ip_input.c:255 dst_input include/net/dst.h:450 [inline] ip_rcv_finish+0x1e1/0x300 net/ipv4/ip_input.c:413 NF_HOOK include/linux/netfilter.h:289 [inline] NF_HOOK include/linux/netfilter.h:283 [inline] ip_rcv+0xe8/0x3f0 net/ipv4/ip_input.c:523 __netif_receive_skb_one_core+0x115/0x1a0 net/core/dev.c:4987 __netif_receive_skb+0x2c/0x1c0 net/core/dev.c:5099 netif_receive_skb_internal+0x117/0x660 net/core/dev.c:5202 napi_frags_finish net/core/dev.c:5769 [inline] napi_gro_frags+0xade/0xd10 net/core/dev.c:5843 tun_get_user+0x2f24/0x3fb0 drivers/net/tun.c:1981 tun_chr_write_iter+0xbd/0x156 drivers/net/tun.c:2027 call_write_iter include/linux/fs.h:1866 [inline] do_iter_readv_writev+0x5e1/0x8e0 fs/read_write.c:681 do_iter_write fs/read_write.c:957 [inline] do_iter_write+0x184/0x610 fs/read_write.c:938 vfs_writev+0x1b3/0x2f0 fs/read_write.c:1002 do_writev+0x15e/0x370 fs/read_write.c:1037 __do_sys_writev fs/read_write.c:1110 [inline] __se_sys_writev fs/read_write.c:1107 [inline] __x64_sys_writev+0x75/0xb0 fs/read_write.c:1107 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fixes: 5271953cad31 ("rxrpc: Use the UDP encap_rcv hook") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Acked-by: David Howells dhowells@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/rxrpc/input.c | 12 ++++++++---- net/rxrpc/local_object.c | 3 ++- 2 files changed, 10 insertions(+), 5 deletions(-)
--- a/net/rxrpc/input.c +++ b/net/rxrpc/input.c @@ -1155,19 +1155,19 @@ int rxrpc_extract_header(struct rxrpc_sk * handle data received on the local endpoint * - may be called in interrupt context * - * The socket is locked by the caller and this prevents the socket from being - * shut down and the local endpoint from going away, thus sk_user_data will not - * be cleared until this function returns. + * [!] Note that as this is called from the encap_rcv hook, the socket is not + * held locked by the caller and nothing prevents sk_user_data on the UDP from + * being cleared in the middle of processing this function. * * Called with the RCU read lock held from the IP layer via UDP. */ int rxrpc_input_packet(struct sock *udp_sk, struct sk_buff *skb) { + struct rxrpc_local *local = rcu_dereference_sk_user_data(udp_sk); struct rxrpc_connection *conn; struct rxrpc_channel *chan; struct rxrpc_call *call = NULL; struct rxrpc_skb_priv *sp; - struct rxrpc_local *local = udp_sk->sk_user_data; struct rxrpc_peer *peer = NULL; struct rxrpc_sock *rx = NULL; unsigned int channel; @@ -1175,6 +1175,10 @@ int rxrpc_input_packet(struct sock *udp_
_enter("%p", udp_sk);
+ if (unlikely(!local)) { + kfree_skb(skb); + return 0; + } if (skb->tstamp == 0) skb->tstamp = ktime_get_real();
--- a/net/rxrpc/local_object.c +++ b/net/rxrpc/local_object.c @@ -304,7 +304,8 @@ nomem: ret = -ENOMEM; sock_error: mutex_unlock(&rxnet->local_mutex); - kfree(local); + if (local) + call_rcu(&local->rcu, rxrpc_local_rcu); _leave(" = %d", ret); return ERR_PTR(ret);