6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet edumazet@google.com
[ Upstream commit aec7291003df78cb71fd461d7b672912bde55807 ]
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@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/66f661e2.050a0220.38ace9.000f.GAE@google.com/... Signed-off-by: Eric Dumazet edumazet@google.com Cc: Tom Parkin tparkin@katalix.com Cc: James Chapman jchapman@katalix.com Link: https://patch.msgid.link/20240927074553.341910-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 5a6fa566e722f..de14e89619c5e 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();