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Message-ID: <20250103210514.87290-1-edumazet@google.com>
Date: Fri, 3 Jan 2025 21:05:14 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, Simon Horman <horms@...nel.org>,
Kuniyuki Iwashima <kuniyu@...zon.com>, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>, syzbot <syzkaller@...glegroups.com>
Subject: [PATCH net-next] ax25: rcu protect dev->ax25_ptr
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@...glegroups.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
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 2593019ad5b1614f3b8c037afb4ba4fa740c7d51..e84602e0226c1c520435f35bb22b1aaf36db2dd1 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2261,7 +2261,7 @@ 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 cb622d84cd0cc4570705774036a843c8c075a328..4ee141aae0a29de4655c9f72be1f21910b89d4a3 100644
--- a/include/net/ax25.h
+++ b/include/net/ax25.h
@@ -231,6 +231,7 @@ typedef struct ax25_dev {
#endif
refcount_t refcount;
bool device_up;
+ struct rcu_head rcu;
} ax25_dev;
typedef struct ax25_cb {
@@ -290,9 +291,8 @@ 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)
{
@@ -335,9 +335,9 @@ 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 d6f9fae06a9d8139ec0505358327e3876af228ae..aa6c714892ec9dcaa5617fdc96e0174b0fbd1041 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 9efd6690b3443653a2f2ef421080aa48b214a8ba..3733c0254a50842fed496bfd983d9d5633ea8ea4 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -90,7 +90,7 @@ 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);
@@ -125,7 +125,7 @@ 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 36249776c021e725512e156c773aead2afea1d13..215d4ccf12b91319580b5af9f9a9abcbe565df49 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 3db76d2470e954cc3de1a8a1f536cc2021cb0912..8bca2ace98e51b6bf79691406c3b9484ef6372f7 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 b7c4d656a94b7107aa93a62a0c6db569babab2ca..69de75db0c9c2155f81a1161b456f4c3864bb246 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;
}
--
2.47.1.613.gc27f4b7a9f-goog
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