Commit 17586822 authored Jan 03, 2025 by Eric Dumazet Committed by Wentao Guan Mar 25, 2025

ax25: rcu protect dev->ax25_ptr

stable inclusion
from stable-v6.6.76
commit 7705d8a7f2c26c80973c81093db07c6022b2b30e
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IBW08Q

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7705d8a7f2c26c80973c81093db07c6022b2b30e



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

[ Upstream commit 95fc45d1dea8e1253f8ec58abc5befb71553d666 ]

syzbot found a lockdep issue [1].

We should remove ax25 RTNL dependency in ax25_setsockopt()

This should also fix a variety of possible UAF in ax25.

[1]

WARNING: possible circular locking dependency detected
6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Not tainted
------------------------------------------------------
syz.5.1818/12806 is trying to acquire lock:
 ffffffff8fcb3988 (rtnl_mutex){+.+.}-{4:4}, at: ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680

but task is already holding lock:
 ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline]
 ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_AX25){+.+.}-{0:0}:
        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
        lock_sock_nested+0x48/0x100 net/core/sock.c:3642
        lock_sock include/net/sock.h:1618 [inline]
        ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]
        ax25_device_event+0x24d/0x580 net/ax25/af_ax25.c:146
        notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85
       __dev_notify_flags+0x207/0x400
        dev_change_flags+0xf0/0x1a0 net/core/dev.c:9026
        dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:563
        dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:820
        sock_do_ioctl+0x240/0x460 net/socket.c:1234
        sock_ioctl+0x626/0x8e0 net/socket.c:1339
        vfs_ioctl fs/ioctl.c:51 [inline]
        __do_sys_ioctl fs/ioctl.c:906 [inline]
        __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
        do_syscall_x64 arch/x86/entry/common.c:52 [inline]
        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (rtnl_mutex){+.+.}-{4:4}:
        check_prev_add kernel/locking/lockdep.c:3161 [inline]
        check_prevs_add kernel/locking/lockdep.c:3280 [inline]
        validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
        __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
        __mutex_lock_common kernel/locking/mutex.c:585 [inline]
        __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
        ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680
        do_sock_setsockopt+0x3af/0x720 net/socket.c:2324
        __sys_setsockopt net/socket.c:2349 [inline]
        __do_sys_setsockopt net/socket.c:2355 [inline]
        __se_sys_setsockopt net/socket.c:2352 [inline]
        __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2352
        do_syscall_x64 arch/x86/entry/common.c:52 [inline]
        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sk_lock-AF_AX25);
                               lock(rtnl_mutex);
                               lock(sk_lock-AF_AX25);
  lock(rtnl_mutex);

 *** DEADLOCK ***

1 lock held by syz.5.1818/12806:
  #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline]
  #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574

stack backtrace:
CPU: 1 UID: 0 PID: 12806 Comm: syz.5.1818 Not tainted 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
  __dump_stack lib/dump_stack.c:94 [inline]
  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
  print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
  check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
  check_prev_add kernel/locking/lockdep.c:3161 [inline]
  check_prevs_add kernel/locking/lockdep.c:3280 [inline]
  validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
  __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
  lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
  __mutex_lock_common kernel/locking/mutex.c:585 [inline]
  __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
  ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680
  do_sock_setsockopt+0x3af/0x720 net/socket.c:2324
  __sys_setsockopt net/socket.c:2349 [inline]
  __do_sys_setsockopt net/socket.c:2355 [inline]
  __se_sys_setsockopt net/socket.c:2352 [inline]
  __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2352
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7b62385d29

Fixes: c4335704 ("ax25: fix a use-after-free in ax25_fillin_cb()")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250103210514.87290-1-edumazet@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 7705d8a7f2c26c80973c81093db07c6022b2b30e)
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>

parent f146cbc2

include/linux/netdevice.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -2245,7 +2245,7 @@ struct net_device {
		void *atalk_ptr;
		#endif
		#if IS_ENABLED(CONFIG_AX25)
		void *ax25_ptr;
		struct ax25_dev __rcu *ax25_ptr;
		#endif
		#if IS_ENABLED(CONFIG_CFG80211)
		struct wireless_dev *ieee80211_ptr;

include/net/ax25.h

+5 −5

Original line number	Diff line number	Diff line
		@@ -229,6 +229,7 @@ typedef struct ax25_dev {
		#endif
		refcount_t refcount;
		bool device_up;
		struct rcu_head rcu;
		} ax25_dev;

		typedef struct ax25_cb {
		@@ -288,9 +289,8 @@ static inline void ax25_dev_hold(ax25_dev *ax25_dev)

		static inline void ax25_dev_put(ax25_dev *ax25_dev)
		{
		if (refcount_dec_and_test(&ax25_dev->refcount)) {
		kfree(ax25_dev);
		}
		if (refcount_dec_and_test(&ax25_dev->refcount))
		kfree_rcu(ax25_dev, rcu);
		}
		static inline __be16 ax25_type_trans(struct sk_buff skb, struct net_device dev)
		{
		@@ -333,9 +333,9 @@ void ax25_digi_invert(const ax25_digi , ax25_digi );
		extern spinlock_t ax25_dev_lock;

		#if IS_ENABLED(CONFIG_AX25)
		static inline ax25_dev ax25_dev_ax25dev(struct net_device dev)
		static inline ax25_dev ax25_dev_ax25dev(const struct net_device dev)
		{
		return dev->ax25_ptr;
		return rcu_dereference_rtnl(dev->ax25_ptr);
		}
		#endif

net/ax25/af_ax25.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -467,7 +467,7 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
		goto out_put;
		}

		static void ax25_fillin_cb_from_dev(ax25_cb ax25, ax25_dev ax25_dev)
		static void ax25_fillin_cb_from_dev(ax25_cb ax25, const ax25_dev ax25_dev)
		{
		ax25->rtt = msecs_to_jiffies(ax25_dev->values[AX25_VALUES_T1]) / 2;
		ax25->t1 = msecs_to_jiffies(ax25_dev->values[AX25_VALUES_T1]);
		@@ -677,22 +677,22 @@ static int ax25_setsockopt(struct socket *sock, int level, int optname,
		break;
		}

		rtnl_lock();
		dev = __dev_get_by_name(&init_net, devname);
		rcu_read_lock();
		dev = dev_get_by_name_rcu(&init_net, devname);
		if (!dev) {
		rtnl_unlock();
		rcu_read_unlock();
		res = -ENODEV;
		break;
		}

		ax25->ax25_dev = ax25_dev_ax25dev(dev);
		if (!ax25->ax25_dev) {
		rtnl_unlock();
		rcu_read_unlock();
		res = -ENODEV;
		break;
		}
		ax25_fillin_cb(ax25, ax25->ax25_dev);
		rtnl_unlock();
		rcu_read_unlock();
		break;

		default:

net/ax25/ax25_dev.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -87,7 +87,7 @@ void ax25_dev_device_up(struct net_device *dev)

		spin_lock_bh(&ax25_dev_lock);
		list_add(&ax25_dev->list, &ax25_dev_list);
		dev->ax25_ptr = ax25_dev;
		rcu_assign_pointer(dev->ax25_ptr, ax25_dev);
		spin_unlock_bh(&ax25_dev_lock);

		ax25_register_dev_sysctl(ax25_dev);
		@@ -122,7 +122,7 @@ void ax25_dev_device_down(struct net_device *dev)
		}
		}

		dev->ax25_ptr = NULL;
		RCU_INIT_POINTER(dev->ax25_ptr, NULL);
		spin_unlock_bh(&ax25_dev_lock);
		netdev_put(dev, &ax25_dev->dev_tracker);
		ax25_dev_put(ax25_dev);

net/ax25/ax25_ip.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -122,6 +122,7 @@ netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
		if (dev == NULL)
		dev = skb->dev;

		rcu_read_lock();
		if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) {
		kfree_skb(skb);
		goto put;
		@@ -202,7 +203,7 @@ netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
		ax25_queue_xmit(skb, dev);

		put:

		rcu_read_unlock();
		ax25_route_lock_unuse();
		return NETDEV_TX_OK;
		}