diff options
Diffstat (limited to '0082-net-ax25-Fix-deadlock-caused-by-skb_recv_datagram-in.patch')
| -rw-r--r-- | 0082-net-ax25-Fix-deadlock-caused-by-skb_recv_datagram-in.patch | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/0082-net-ax25-Fix-deadlock-caused-by-skb_recv_datagram-in.patch b/0082-net-ax25-Fix-deadlock-caused-by-skb_recv_datagram-in.patch new file mode 100644 index 000000000000..4710f2b829e5 --- /dev/null +++ b/0082-net-ax25-Fix-deadlock-caused-by-skb_recv_datagram-in.patch @@ -0,0 +1,120 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: Duoming Zhou <duoming@zju.edu.cn> +Date: Tue, 14 Jun 2022 17:25:57 +0800 +Subject: [PATCH] net: ax25: Fix deadlock caused by skb_recv_datagram in + ax25_recvmsg + +[ Upstream commit 219b51a6f040fa5367adadd7d58c4dda0896a01d ] + +The skb_recv_datagram() in ax25_recvmsg() will hold lock_sock +and block until it receives a packet from the remote. If the client +doesn`t connect to server and calls read() directly, it will not +receive any packets forever. As a result, the deadlock will happen. + +The fail log caused by deadlock is shown below: + +[ 369.606973] INFO: task ax25_deadlock:157 blocked for more than 245 seconds. +[ 369.608919] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. +[ 369.613058] Call Trace: +[ 369.613315] <TASK> +[ 369.614072] __schedule+0x2f9/0xb20 +[ 369.615029] schedule+0x49/0xb0 +[ 369.615734] __lock_sock+0x92/0x100 +[ 369.616763] ? destroy_sched_domains_rcu+0x20/0x20 +[ 369.617941] lock_sock_nested+0x6e/0x70 +[ 369.618809] ax25_bind+0xaa/0x210 +[ 369.619736] __sys_bind+0xca/0xf0 +[ 369.620039] ? do_futex+0xae/0x1b0 +[ 369.620387] ? __x64_sys_futex+0x7c/0x1c0 +[ 369.620601] ? fpregs_assert_state_consistent+0x19/0x40 +[ 369.620613] __x64_sys_bind+0x11/0x20 +[ 369.621791] do_syscall_64+0x3b/0x90 +[ 369.622423] entry_SYSCALL_64_after_hwframe+0x46/0xb0 +[ 369.623319] RIP: 0033:0x7f43c8aa8af7 +[ 369.624301] RSP: 002b:00007f43c8197ef8 EFLAGS: 00000246 ORIG_RAX: 0000000000000031 +[ 369.625756] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f43c8aa8af7 +[ 369.626724] RDX: 0000000000000010 RSI: 000055768e2021d0 RDI: 0000000000000005 +[ 369.628569] RBP: 00007f43c8197f00 R08: 0000000000000011 R09: 00007f43c8198700 +[ 369.630208] R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff845e6afe +[ 369.632240] R13: 00007fff845e6aff R14: 00007f43c8197fc0 R15: 00007f43c8198700 + +This patch replaces skb_recv_datagram() with an open-coded variant of it +releasing the socket lock before the __skb_wait_for_more_packets() call +and re-acquiring it after such call in order that other functions that +need socket lock could be executed. + +what's more, the socket lock will be released only when recvmsg() will +block and that should produce nicer overall behavior. + +Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") +Suggested-by: Thomas Osterried <thomas@osterried.de> +Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> +Reported-by: Thomas Habets <thomas@@habets.se> +Acked-by: Paolo Abeni <pabeni@redhat.com> +Reviewed-by: Eric Dumazet <edumazet@google.com> +Signed-off-by: David S. Miller <davem@davemloft.net> +Signed-off-by: Sasha Levin <sashal@kernel.org> +--- + net/ax25/af_ax25.c | 33 ++++++++++++++++++++++++++++----- + 1 file changed, 28 insertions(+), 5 deletions(-) + +diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c +index 95393bb2760b3e322d531679451c81e2a3877b29..4c7030ed8d3319448f6cb158417c650308e341b8 100644 +--- a/net/ax25/af_ax25.c ++++ b/net/ax25/af_ax25.c +@@ -1661,9 +1661,12 @@ static int ax25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size, + int flags) + { + struct sock *sk = sock->sk; +- struct sk_buff *skb; ++ struct sk_buff *skb, *last; ++ struct sk_buff_head *sk_queue; + int copied; + int err = 0; ++ int off = 0; ++ long timeo; + + lock_sock(sk); + /* +@@ -1675,10 +1678,29 @@ static int ax25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size, + goto out; + } + +- /* Now we can treat all alike */ +- skb = skb_recv_datagram(sk, flags, &err); +- if (skb == NULL) +- goto out; ++ /* We need support for non-blocking reads. */ ++ sk_queue = &sk->sk_receive_queue; ++ skb = __skb_try_recv_datagram(sk, sk_queue, flags, &off, &err, &last); ++ /* If no packet is available, release_sock(sk) and try again. */ ++ if (!skb) { ++ if (err != -EAGAIN) ++ goto out; ++ release_sock(sk); ++ timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT); ++ while (timeo && !__skb_wait_for_more_packets(sk, sk_queue, &err, ++ &timeo, last)) { ++ skb = __skb_try_recv_datagram(sk, sk_queue, flags, &off, ++ &err, &last); ++ if (skb) ++ break; ++ ++ if (err != -EAGAIN) ++ goto done; ++ } ++ if (!skb) ++ goto done; ++ lock_sock(sk); ++ } + + if (!sk_to_ax25(sk)->pidincl) + skb_pull(skb, 1); /* Remove PID */ +@@ -1725,6 +1747,7 @@ static int ax25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size, + out: + release_sock(sk); + ++done: + return err; + } + |