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Duoming Zhou 64072389be net: ax25: Fix deadlock caused by skb_recv_datagram in ax25_recvmsg [ Upstream commit `219b51a6f0` ] 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> Signed-off-by: Sasha Levin <sashal@kernel.org>		2022-06-22 14:13:17 +02:00
arch	powerpc/kasan: Silence KASAN warnings in __get_wchan()	2022-06-22 14:13:13 +02:00
block	block: fix bio_clone_blkg_association() to associate with proper blkcg_gq	2022-06-09 10:21:31 +02:00
certs	certs: Trigger creation of RSA module signing key if it's not an RSA key	2021-09-15 09:50:29 +02:00
crypto	crypto: cryptd - Protect per-CPU resource by disabling BH.	2022-06-09 10:21:17 +02:00
Documentation	x86/speculation/mmio: Add sysfs reporting for Processor MMIO Stale Data	2022-06-16 13:27:59 +02:00
drivers	net: bgmac: Fix an erroneous kfree() in bgmac_remove()	2022-06-22 14:13:17 +02:00
fs	pNFS: Avoid a live lock condition in pnfs_update_layout()	2022-06-22 14:13:16 +02:00
include	x86/speculation/mmio: Add sysfs reporting for Processor MMIO Stale Data	2022-06-16 13:27:59 +02:00
init	Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug	2022-06-09 10:21:25 +02:00
ipc	ipc/mqueue: use get_tree_nodev() in mqueue_get_tree()	2022-06-09 10:21:17 +02:00
kernel	dma-debug: make things less spammy under memory pressure	2022-06-22 14:13:13 +02:00
lib	nodemask: Fix return values to be unsigned	2022-06-14 18:32:45 +02:00
LICENSES	LICENSES/deprecated: add Zlib license text	2020-09-16 14:33:49 +02:00
mm	hugetlb: fix huge_pmd_unshare address update	2022-06-09 10:21:27 +02:00
net	net: ax25: Fix deadlock caused by skb_recv_datagram in ax25_recvmsg	2022-06-22 14:13:17 +02:00
samples	samples/bpf, xdpsock: Fix race when running for fix duration of time	2022-04-08 14:40:21 +02:00
scripts	scripts/gdb: change kernel config dumping method	2022-06-14 18:32:45 +02:00
security	ima: remove the IMA_TEMPLATE Kconfig option	2022-06-09 10:21:25 +02:00
sound	ALSA: hda/realtek - Add HW8326 support	2022-06-22 14:13:15 +02:00
tools	KVM: x86/speculation: Disable Fill buffer clear within guests	2022-06-16 13:27:59 +02:00
usr	usr/include/Makefile: add linux/nfc.h to the compile-test coverage	2022-02-01 17:25:48 +01:00
virt	KVM: Prevent module exit until all VMs are freed	2022-04-08 14:40:38 +02:00
.clang-format	RDMA 5.10 pull request	2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore	Opt out of scripts/get_maintainer.pl	2019-05-16 10:53:40 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	kbuild: generate Module.symvers only when vmlinux exists	2021-05-19 10:12:59 +02:00
.mailmap	mailmap: add two more addresses of Uwe Kleine-König	2020-12-06 10:19:07 -08:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Move Jason Cooper to CREDITS	2020-11-30 10:20:34 +01:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	MAINTAINERS: add git tree for random.c	2022-05-30 09:33:24 +02:00
Makefile	Linux 5.10.123	2022-06-16 13:28:00 +02:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.