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Message-ID: <20240927074553.341910-1-edumazet@google.com>
Date: Fri, 27 Sep 2024 07:45:53 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>, syzbot+bd8d55ee2acd0a71d8ce@...kaller.appspotmail.com,
Tom Parkin <tparkin@...alix.com>, James Chapman <jchapman@...alix.com>
Subject: [PATCH net] ppp: do not assume bh is held in ppp_channel_bridge_input()
Networking receive path is usually handled from BH handler.
However, some protocols need to acquire the socket lock, and
packets might be stored in the socket backlog is the socket was
owned by a user process.
In this case, release_sock(), __release_sock(), and sk_backlog_rcv()
might call the sk->sk_backlog_rcv() handler in process context.
sybot caught ppp was not considering this case in
ppp_channel_bridge_input() :
WARNING: inconsistent lock state
6.11.0-rc7-syzkaller-g5f5673607153 #0 Not tainted
--------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
ksoftirqd/1/24 [HC0[0]:SC1[1]:HE1:SE0] takes:
ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline]
ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: ppp_input+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304
{SOFTIRQ-ON-W} state was registered at:
lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x48/0x60 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline]
ppp_input+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304
pppoe_rcv_core+0xfc/0x314 drivers/net/ppp/pppoe.c:379
sk_backlog_rcv include/net/sock.h:1111 [inline]
__release_sock+0x1a8/0x3d8 net/core/sock.c:3004
release_sock+0x68/0x1b8 net/core/sock.c:3558
pppoe_sendmsg+0xc8/0x5d8 drivers/net/ppp/pppoe.c:903
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
__sys_sendto+0x374/0x4f4 net/socket.c:2204
__do_sys_sendto net/socket.c:2216 [inline]
__se_sys_sendto net/socket.c:2212 [inline]
__arm64_sys_sendto+0xd8/0xf8 net/socket.c:2212
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
irq event stamp: 282914
hardirqs last enabled at (282914): [<ffff80008b42e30c>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
hardirqs last enabled at (282914): [<ffff80008b42e30c>] _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:194
hardirqs last disabled at (282913): [<ffff80008b42e13c>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline]
hardirqs last disabled at (282913): [<ffff80008b42e13c>] _raw_spin_lock_irqsave+0x2c/0x7c kernel/locking/spinlock.c:162
softirqs last enabled at (282904): [<ffff8000801f8e88>] softirq_handle_end kernel/softirq.c:400 [inline]
softirqs last enabled at (282904): [<ffff8000801f8e88>] handle_softirqs+0xa3c/0xbfc kernel/softirq.c:582
softirqs last disabled at (282909): [<ffff8000801fbdf8>] run_ksoftirqd+0x70/0x158 kernel/softirq.c:928
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&pch->downl);
<Interrupt>
lock(&pch->downl);
*** DEADLOCK ***
1 lock held by ksoftirqd/1/24:
#0: ffff80008f74dfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:325
stack backtrace:
CPU: 1 UID: 0 PID: 24 Comm: ksoftirqd/1 Not tainted 6.11.0-rc7-syzkaller-g5f5673607153 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Call trace:
dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:319
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:326
__dump_stack lib/dump_stack.c:93 [inline]
dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:119
dump_stack+0x1c/0x28 lib/dump_stack.c:128
print_usage_bug+0x698/0x9ac kernel/locking/lockdep.c:4000
mark_lock_irq+0x980/0xd2c
mark_lock+0x258/0x360 kernel/locking/lockdep.c:4677
__lock_acquire+0xf48/0x779c kernel/locking/lockdep.c:5096
lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x48/0x60 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline]
ppp_input+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304
ppp_async_process+0x98/0x150 drivers/net/ppp/ppp_async.c:495
tasklet_action_common+0x318/0x3f4 kernel/softirq.c:785
tasklet_action+0x68/0x8c kernel/softirq.c:811
handle_softirqs+0x2e4/0xbfc kernel/softirq.c:554
run_ksoftirqd+0x70/0x158 kernel/softirq.c:928
smpboot_thread_fn+0x4b0/0x90c kernel/smpboot.c:164
kthread+0x288/0x310 kernel/kthread.c:389
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860
Fixes: 4cf476ced45d ("ppp: add PPPIOCBRIDGECHAN and PPPIOCUNBRIDGECHAN ioctls")
Reported-by: syzbot+bd8d55ee2acd0a71d8ce@...kaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/66f661e2.050a0220.38ace9.000f.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Tom Parkin <tparkin@...alix.com>
Cc: James Chapman <jchapman@...alix.com>
---
drivers/net/ppp/ppp_generic.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 4b2971e2bf484a13b5e94ac3b9862224adac4c41..0d5cd705decb1fe19d15848125beabda40edf46b 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -2269,7 +2269,7 @@ static bool ppp_channel_bridge_input(struct channel *pch, struct sk_buff *skb)
if (!pchb)
goto out_rcu;
- spin_lock(&pchb->downl);
+ spin_lock_bh(&pchb->downl);
if (!pchb->chan) {
/* channel got unregistered */
kfree_skb(skb);
@@ -2281,7 +2281,7 @@ static bool ppp_channel_bridge_input(struct channel *pch, struct sk_buff *skb)
kfree_skb(skb);
outl:
- spin_unlock(&pchb->downl);
+ spin_unlock_bh(&pchb->downl);
out_rcu:
rcu_read_unlock();
--
2.46.1.824.gd892dcdcdd-goog
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