Hello Eric, Jakub,

the patch that needs to be fixed here is currently already on its way into the stable trees:

Fixes: ee8b94c8510c ("can: raw: fix receiver memory leak")

Should this patch go through the linux-can tree or would somebody like to apply it directly to the net tree?

Many thanks, Oliver

On 20.07.23 13:44, Eric Dumazet wrote:

syzbot complained about a lockdep issue [1]

Since raw_bind() and raw_setsockopt() first get RTNL before locking the socket, we must adopt the same order in raw_release()

[1] WARNING: possible circular locking dependency detected 6.5.0-rc1-syzkaller-00192-g78adb4bcf99e #0 Not tainted

---

syz-executor.0/14110 is trying to acquire lock: ffff88804e4b6130 (sk_lock-AF_CAN){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1708 [inline] ffff88804e4b6130 (sk_lock-AF_CAN){+.+.}-{0:0}, at: raw_bind+0xb1/0xab0 net/can/raw.c:435

but task is already holding lock: ffffffff8e3df368 (rtnl_mutex){+.+.}-{3:3}, at: raw_bind+0xa7/0xab0 net/can/raw.c:434

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (rtnl_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x181/0x1340 kernel/locking/mutex.c:747 raw_release+0x1c6/0x9b0 net/can/raw.c:391 __sock_release+0xcd/0x290 net/socket.c:654 sock_close+0x1c/0x20 net/socket.c:1386 __fput+0x3fd/0xac0 fs/file_table.c:384 task_work_run+0x14d/0x240 kernel/task_work.c:179 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop kernel/entry/common.c:171 [inline] exit_to_user_mode_prepare+0x210/0x240 kernel/entry/common.c:204 __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline] syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:297 do_syscall_64+0x44/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (sk_lock-AF_CAN){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3142 [inline] check_prevs_add kernel/locking/lockdep.c:3261 [inline] validate_chain kernel/locking/lockdep.c:3876 [inline] __lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5144 lock_acquire kernel/locking/lockdep.c:5761 [inline] lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5726 lock_sock_nested+0x3a/0xf0 net/core/sock.c:3492 lock_sock include/net/sock.h:1708 [inline] raw_bind+0xb1/0xab0 net/can/raw.c:435 __sys_bind+0x1ec/0x220 net/socket.c:1792 __do_sys_bind net/socket.c:1803 [inline] __se_sys_bind net/socket.c:1801 [inline] __x64_sys_bind+0x72/0xb0 net/socket.c:1801 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1

---

lock(rtnl_mutex); lock(sk_lock-AF_CAN); lock(rtnl_mutex); lock(sk_lock-AF_CAN);

*** DEADLOCK ***

1 lock held by syz-executor.0/14110:

stack backtrace: CPU: 0 PID: 14110 Comm: syz-executor.0 Not tainted 6.5.0-rc1-syzkaller-00192-g78adb4bcf99e #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 Call Trace:

<TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 check_noncircular+0x311/0x3f0 kernel/locking/lockdep.c:2195 check_prev_add kernel/locking/lockdep.c:3142 [inline] check_prevs_add kernel/locking/lockdep.c:3261 [inline] validate_chain kernel/locking/lockdep.c:3876 [inline] __lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5144 lock_acquire kernel/locking/lockdep.c:5761 [inline] lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5726 lock_sock_nested+0x3a/0xf0 net/core/sock.c:3492 lock_sock include/net/sock.h:1708 [inline] raw_bind+0xb1/0xab0 net/can/raw.c:435 __sys_bind+0x1ec/0x220 net/socket.c:1792 __do_sys_bind net/socket.c:1803 [inline] __se_sys_bind net/socket.c:1801 [inline] __x64_sys_bind+0x72/0xb0 net/socket.c:1801 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7fd89007cb29 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fd890d2a0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000031 RAX: ffffffffffffffda RBX: 00007fd89019bf80 RCX: 00007fd89007cb29 RDX: 0000000000000010 RSI: 0000000020000040 RDI: 0000000000000003 RBP: 00007fd8900c847a R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000000000b R14: 00007fd89019bf80 R15: 00007ffebf8124f8 </TASK>

Fixes: ee8b94c8510c ("can: raw: fix receiver memory leak") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Eric Dumazet edumazet@google.com Cc: Ziyang Xuan william.xuanziyang@huawei.com Cc: Oliver Hartkopp socketcan@hartkopp.net Cc: stable@vger.kernel.org Cc: Marc Kleine-Budde mkl@pengutronix.de

---

net/can/raw.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/can/raw.c b/net/can/raw.c index 2302e48829677334f8b2d74a479e5a9cbb5ce03c..ba6b52b1d7767fdd7b57d1b8e5519495340c572c 100644 --- a/net/can/raw.c +++ b/net/can/raw.c @@ -386,9 +386,9 @@ static int raw_release(struct socket *sock) list_del(&ro->notifier); spin_unlock(&raw_notifier_lock);

• rtnl_lock(); lock_sock(sk);

• rtnl_lock(); /* remove current filters & unregister */ if (ro->bound) { if (ro->dev)

@@ -405,12 +405,13 @@ static int raw_release(struct socket *sock) ro->dev = NULL; ro->count = 0; free_percpu(ro->uniq);

• rtnl_unlock();

sock_orphan(sk); sock->sk = NULL; release_sock(sk);

• rtnl_unlock();
• sock_put(sk);

return 0;