6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet edumazet@google.com
[ 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: c433570458e4 ("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 --- include/linux/netdevice.h | 2 +- include/net/ax25.h | 10 +++++----- net/ax25/af_ax25.c | 12 ++++++------ net/ax25/ax25_dev.c | 4 ++-- net/ax25/ax25_ip.c | 3 ++- net/ax25/ax25_out.c | 22 +++++++++++++++++----- net/ax25/ax25_route.c | 2 ++ 7 files changed, 35 insertions(+), 20 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 662183994e885..c75aed1fff7d1 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2177,7 +2177,7 @@ 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; diff --git a/include/net/ax25.h b/include/net/ax25.h index 1d55e8ee08b4f..e9465aa07a4e7 100644 --- a/include/net/ax25.h +++ b/include/net/ax25.h @@ -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 { @@ -291,9 +292,8 @@ 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) { @@ -336,9 +336,9 @@ 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
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index a1e0be8716870..4b96dedcc3c9c 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -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: diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c index e165fe108bb00..2b4f8df53b765 100644 --- a/net/ax25/ax25_dev.c +++ b/net/ax25/ax25_dev.c @@ -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); diff --git a/net/ax25/ax25_ip.c b/net/ax25/ax25_ip.c index 36249776c021e..215d4ccf12b91 100644 --- a/net/ax25/ax25_ip.c +++ b/net/ax25/ax25_ip.c @@ -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; } diff --git a/net/ax25/ax25_out.c b/net/ax25/ax25_out.c index 3db76d2470e95..8bca2ace98e51 100644 --- a/net/ax25/ax25_out.c +++ b/net/ax25/ax25_out.c @@ -39,10 +39,14 @@ ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, const ax25_address *sr * specified. */ if (paclen == 0) { - if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) + rcu_read_lock(); + ax25_dev = ax25_dev_ax25dev(dev); + if (!ax25_dev) { + rcu_read_unlock(); return NULL; - + } paclen = ax25_dev->values[AX25_VALUES_PACLEN]; + rcu_read_unlock(); }
/* @@ -53,13 +57,19 @@ ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, const ax25_address *sr return ax25; /* It already existed */ }
- if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) + rcu_read_lock(); + ax25_dev = ax25_dev_ax25dev(dev); + if (!ax25_dev) { + rcu_read_unlock(); return NULL; + }
- if ((ax25 = ax25_create_cb()) == NULL) + if ((ax25 = ax25_create_cb()) == NULL) { + rcu_read_unlock(); return NULL; - + } ax25_fillin_cb(ax25, ax25_dev); + rcu_read_unlock();
ax25->source_addr = *src; ax25->dest_addr = *dest; @@ -358,7 +368,9 @@ void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev) { unsigned char *ptr;
+ rcu_read_lock(); skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev)); + rcu_read_unlock();
ptr = skb_push(skb, 1); *ptr = 0x00; /* KISS */ diff --git a/net/ax25/ax25_route.c b/net/ax25/ax25_route.c index b7c4d656a94b7..69de75db0c9c2 100644 --- a/net/ax25/ax25_route.c +++ b/net/ax25/ax25_route.c @@ -406,6 +406,7 @@ int ax25_rt_autobind(ax25_cb *ax25, ax25_address *addr) ax25_route_lock_unuse(); return -EHOSTUNREACH; } + rcu_read_lock(); if ((ax25->ax25_dev = ax25_dev_ax25dev(ax25_rt->dev)) == NULL) { err = -EHOSTUNREACH; goto put; @@ -442,6 +443,7 @@ int ax25_rt_autobind(ax25_cb *ax25, ax25_address *addr) }
put: + rcu_read_unlock(); ax25_route_lock_unuse(); return err; }