Duoming Zhou 219b51a6f0 net: ax25: Fix deadlock caused by skb_recv_datagram in ax25_recvmsg ... 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: 1da177e4c3 ("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>		2022-06-15 13:00:22 +01:00
..
af_ax25.c	net: ax25: Fix deadlock caused by skb_recv_datagram in ax25_recvmsg	2022-06-15 13:00:22 +01:00
ax25_addr.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
ax25_dev.c	ax25: Fix ax25 session cleanup problems	2022-06-02 10:37:57 +02:00
ax25_ds_in.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
ax25_ds_subr.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
ax25_ds_timer.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
ax25_iface.c	ax25: constify dev_addr passing	2021-10-13 09:40:45 -07:00
ax25_in.c	ax25: constify dev_addr passing	2021-10-13 09:40:45 -07:00
ax25_ip.c	ax25: use skb_expand_head	2021-08-03 11:21:39 +01:00
ax25_out.c	ax25: constify dev_addr passing	2021-10-13 09:40:45 -07:00
ax25_route.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net	2022-02-03 17:36:16 -08:00
ax25_std_in.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
ax25_std_subr.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
ax25_std_timer.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
ax25_subr.c	ax25: Fix ax25 session cleanup problems	2022-06-02 10:37:57 +02:00
ax25_timer.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
ax25_uid.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
Kconfig	AX.25 Kconfig: Replace HTTP links with HTTPS ones	2020-07-13 12:34:06 -07:00
Makefile	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
sysctl_net_ax25.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00