From 49054556289e8787501630b7c7a9d407da02e296 Mon Sep 17 00:00:00 2001

From: Paolo Abeni <pabeni@redhat.com>

Date: Wed, 29 Sep 2021 11:59:17 +0200

Subject: [PATCH] net: introduce and use lock_sock_fast_nested()

Git-commit: 49054556289e8787501630b7c7a9d407da02e296

Patch-mainline: v5.15-rc4

References: git-fixes

Syzkaller reported a false positive deadlock involving

the nl socket lock and the subflow socket lock:

Mptcp: kernel_bind error, err=-98

============================================

Warning: possible recursive locking detected

5.15.0-rc1-syzkaller #0 Not tainted

Acked-by: Takashi Iwai <tiwai@suse.de>

--------------------------------------------

syz-executor998/6520 is trying to acquire lock:

ffff8880795718a0 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_close+0x267/0x7b0 net/mptcp/protocol.c:2738

but task is already holding lock:

ffff8880787c8c60 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1612 [inline]

ffff8880787c8c60 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_close+0x23/0x7b0 net/mptcp/protocol.c:2720

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0

       ----

  lock(k-sk_lock-AF_INET);

  lock(k-sk_lock-AF_INET);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

3 locks held by syz-executor998/6520:

 #0: ffffffff8d176c50 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:802

 #1: ffffffff8d176d08 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]

 #1: ffffffff8d176d08 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x3e0/0x580 net/netlink/genetlink.c:790

 #2: ffff8880787c8c60 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1612 [inline]

 #2: ffff8880787c8c60 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_close+0x23/0x7b0 net/mptcp/protocol.c:2720

stack backtrace:

CPU: 1 PID: 6520 Comm: syz-executor998 Not tainted 5.15.0-rc1-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Call Trace:

 __dump_stack lib/dump_stack.c:88 [inline]

 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106

 print_deadlock_bug kernel/locking/lockdep.c:2944 [inline]

 check_deadlock kernel/locking/lockdep.c:2987 [inline]

 validate_chain kernel/locking/lockdep.c:3776 [inline]

 __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5015

 lock_acquire kernel/locking/lockdep.c:5625 [inline]

 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590

 lock_sock_fast+0x36/0x100 net/core/sock.c:3229

 mptcp_close+0x267/0x7b0 net/mptcp/protocol.c:2738

 inet_release+0x12e/0x280 net/ipv4/af_inet.c:431

 __sock_release net/socket.c:649 [inline]

 sock_release+0x87/0x1b0 net/socket.c:677

 mptcp_pm_nl_create_listen_socket+0x238/0x2c0 net/mptcp/pm_netlink.c:900

 mptcp_nl_cmd_add_addr+0x359/0x930 net/mptcp/pm_netlink.c:1170

 genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:731

 genl_family_rcv_msg net/netlink/genetlink.c:775 [inline]

 genl_rcv_msg+0x328/0x580 net/netlink/genetlink.c:792

 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504

 genl_rcv+0x24/0x40 net/netlink/genetlink.c:803

 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]

 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340

 netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929

 sock_sendmsg_nosec net/socket.c:704 [inline]

 sock_sendmsg+0xcf/0x120 net/socket.c:724

 sock_no_sendpage+0x101/0x150 net/core/sock.c:2980

 kernel_sendpage.part.0+0x1a0/0x340 net/socket.c:3504

 kernel_sendpage net/socket.c:3501 [inline]

 sock_sendpage+0xe5/0x140 net/socket.c:1003

 pipe_to_sendpage+0x2ad/0x380 fs/splice.c:364

 splice_from_pipe_feed fs/splice.c:418 [inline]

 __splice_from_pipe+0x43e/0x8a0 fs/splice.c:562

 splice_from_pipe fs/splice.c:597 [inline]

 generic_splice_sendpage+0xd4/0x140 fs/splice.c:746

 do_splice_from fs/splice.c:767 [inline]

 direct_splice_actor+0x110/0x180 fs/splice.c:936

 splice_direct_to_actor+0x34b/0x8c0 fs/splice.c:891

 do_splice_direct+0x1b3/0x280 fs/splice.c:979

 do_sendfile+0xae9/0x1240 fs/read_write.c:1249

 __do_sys_sendfile64 fs/read_write.c:1314 [inline]

 __se_sys_sendfile64 fs/read_write.c:1300 [inline]

 __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1300

 do_syscall_x64 arch/x86/entry/common.c:50 [inline]

 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80

 entry_SYSCALL_64_after_hwframe+0x44/0xae

RIP: 0033:0x7f215cb69969

Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 14 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 c0 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007ffc96bb3868 EFLAGS: 00000246 ORIG_RAX: 0000000000000028

RAX: ffffffffffffffda RBX: 00007f215cbad072 RCX: 00007f215cb69969

RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000005

RBP: 0000000000000000 R08: 00007ffc96bb3a08 R09: 00007ffc96bb3a08

R10: 0000000100000002 R11: 0000000000000246 R12: 00007ffc96bb387c

R13: 431bde82d7b634db R14: 0000000000000000 R15: 0000000000000000

the problem originates from uncorrect lock annotation in the mptcp

code and is only visible since commit 2dcb96bacce3 ("net: core: Correct

the sock::sk_lock.owned lockdep annotations"), but is present since

the port-based endpoint support initial implementation.

This patch addresses the issue introducing a nested variant of

lock_sock_fast() and using it in the relevant code path.

Fixes: 1729cf186d8a ("mptcp: create the listening socket for new port")

Fixes: 2dcb96bacce3 ("net: core: Correct the sock::sk_lock.owned lockdep annotations")

Suggested-by: Thomas Gleixner <tglx@linutronix.de>

Reported-and-tested-by: syzbot+1dd53f7a89b299d59eaf@syzkaller.appspotmail.com

Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

Signed-off-by: David S. Miller <davem@davemloft.net>

---

 include/net/sock.h   | 31 ++++++++++++++++++++++++++++++-

 net/core/sock.c      | 20 ++------------------

 net/mptcp/protocol.c |  2 +-

 3 files changed, 33 insertions(+), 20 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h

index c005c3c750e8..dc3f8169312e 100644

--- a/include/net/sock.h

+++ b/include/net/sock.h

@@ -1623,7 +1623,36 @@ void release_sock(struct sock *sk);

 				SINGLE_DEPTH_NESTING)

 #define bh_unlock_sock(__sk)	spin_unlock(&((__sk)->sk_lock.slock))

-bool lock_sock_fast(struct sock *sk) __acquires(&sk->sk_lock.slock);

+bool __lock_sock_fast(struct sock *sk) __acquires(&sk->sk_lock.slock);

+

+/**

+ * lock_sock_fast - fast version of lock_sock

+ * @sk: socket

+ *

+ * This version should be used for very small section, where process wont block

+ * return false if fast path is taken:

+ *

+ *   sk_lock.slock locked, owned = 0, BH disabled

+ *

+ * return true if slow path is taken:

+ *

+ *   sk_lock.slock unlocked, owned = 1, BH enabled

+ */

+static inline bool lock_sock_fast(struct sock *sk)

+{

+	/* The sk_lock has mutex_lock() semantics here. */

+	mutex_acquire(&sk->sk_lock.dep_map, 0, 0, _RET_IP_);

+

+	return __lock_sock_fast(sk);

+}

+

+/* fast socket lock variant for caller already holding a [different] socket lock */

+static inline bool lock_sock_fast_nested(struct sock *sk)

+{

+	mutex_acquire(&sk->sk_lock.dep_map, SINGLE_DEPTH_NESTING, 0, _RET_IP_);

+

+	return __lock_sock_fast(sk);

+}

 /**

  * unlock_sock_fast - complement of lock_sock_fast

diff --git a/net/core/sock.c b/net/core/sock.c

index 512e629f9780..7060d183216e 100644

--- a/net/core/sock.c

+++ b/net/core/sock.c

@@ -3210,24 +3210,8 @@ void release_sock(struct sock *sk)

 }

 EXPORT_SYMBOL(release_sock);

-/**

- * lock_sock_fast - fast version of lock_sock

- * @sk: socket

- *

- * This version should be used for very small section, where process wont block

- * return false if fast path is taken:

- *

- *   sk_lock.slock locked, owned = 0, BH disabled

- *

- * return true if slow path is taken:

- *

- *   sk_lock.slock unlocked, owned = 1, BH enabled

- */

-bool lock_sock_fast(struct sock *sk) __acquires(&sk->sk_lock.slock)

+bool __lock_sock_fast(struct sock *sk) __acquires(&sk->sk_lock.slock)

 {

-	/* The sk_lock has mutex_lock() semantics here. */

-	mutex_acquire(&sk->sk_lock.dep_map, 0, 0, _RET_IP_);

-

 	might_sleep();

 	spin_lock_bh(&sk->sk_lock.slock);

@@ -3256,7 +3240,7 @@ bool lock_sock_fast(struct sock *sk) __acquires(&sk->sk_lock.slock)

 	spin_unlock_bh(&sk->sk_lock.slock);

 	return true;

 }

-EXPORT_SYMBOL(lock_sock_fast);

+EXPORT_SYMBOL(__lock_sock_fast);

 int sock_gettstamp(struct socket *sock, void __user *userstamp,

 		   bool timeval, bool time32)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c

index dbcebf56798f..e5df0b5971c8 100644

--- a/net/mptcp/protocol.c

+++ b/net/mptcp/protocol.c

@@ -2735,7 +2735,7 @@ static void mptcp_close(struct sock *sk, long timeout)

 	inet_csk(sk)->icsk_mtup.probe_timestamp = tcp_jiffies32;

 	mptcp_for_each_subflow(mptcp_sk(sk), subflow) {

 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);

-		bool slow = lock_sock_fast(ssk);

+		bool slow = lock_sock_fast_nested(ssk);

 		sock_orphan(ssk);

 		unlock_sock_fast(ssk, slow);

-- 

2.26.2