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linux/net/ax25
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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