The deferred-device pass in xfrm_dev_state_flush() finds states under xfrm_state_dev_gc_lock, but drops the lock before calling xfrm_dev_state_free() because the driver callback may sleep. The device GC list does not hold an xfrm_state reference, so the state GC worker can destroy the same state concurrently. The race can proceed as follows: CPU 0 CPU 1 find x on the device GC list drop xfrm_state_dev_gc_lock read x->xso.dev xfrm_state_gc_destroy(x) xfrm_dev_state_free(x) xfrm_state_free(x) continue xfrm_dev_state_free(x) Both paths can invoke the driver callback and drop the device reference. CPU 0 can also access the xfrm_state after CPU 1 has freed it. KASAN reported: BUG: KASAN: slab-use-after-free in xfrm_dev_state_free+0x24c/0x2a0 Read of size 8 at addr ffff88810bbaa960 by task poc/102 Call Trace: xfrm_dev_state_free+0x24c/0x2a0 xfrm_dev_state_flush+0x353/0x400 xfrm_dev_event+0x26d/0x3a0 notifier_call_chain+0xc0/0x280 __dev_notify_flags+0x169/0x250 netif_change_flags+0xe7/0x160 dev_change_flags+0x96/0x220 devinet_ioctl+0x7f4/0x1880 Allocated by task 87: xfrm_state_alloc+0x1e/0x5c0 xfrm_add_sa+0xe7f/0x5820 xfrm_user_rcv_msg+0x4f3/0x940 Freed by task 57: kmem_cache_free+0xcb/0x3d0 xfrm_state_gc_task+0x4a8/0x650 process_one_work+0x63a/0x1070 Serialize xfrm_state destruction against the deferred-device pass with a mutex. Keep xfrm_state_dev_gc_lock limited to list operations and retain the existing callback and device-reference release ordering. Fixes: 07b87f9eea0c ("xfrm: Fix unregister netdevice hang on hardware offload.") Cc: stable@vger.kernel.org Signed-off-by: Chengfeng Ye --- net/xfrm/xfrm_state.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index 36a4f6793ede..de097bba803b 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -226,6 +226,7 @@ static struct xfrm_state_afinfo __rcu *xfrm_state_afinfo[NPROTO]; static DEFINE_SPINLOCK(xfrm_state_gc_lock); static DEFINE_SPINLOCK(xfrm_state_dev_gc_lock); +static DEFINE_MUTEX(xfrm_state_gc_mutex); int __xfrm_state_delete(struct xfrm_state *x); @@ -632,8 +633,10 @@ static void xfrm_state_gc_task(struct work_struct *work) synchronize_rcu(); + mutex_lock(&xfrm_state_gc_mutex); hlist_for_each_entry_safe(x, tmp, &gc_list, gclist) xfrm_state_gc_destroy(x); + mutex_unlock(&xfrm_state_gc_mutex); } static enum hrtimer_restart xfrm_timer_handler(struct hrtimer *me) @@ -1000,6 +1003,7 @@ int xfrm_dev_state_flush(struct net *net, struct net_device *dev, bool task_vali out: spin_unlock_bh(&net->xfrm.xfrm_state_lock); + mutex_lock(&xfrm_state_gc_mutex); spin_lock_bh(&xfrm_state_dev_gc_lock); restart_gc: hlist_for_each_entry_safe(x, tmp, &xfrm_state_dev_gc_list, dev_gclist) { @@ -1014,6 +1018,7 @@ int xfrm_dev_state_flush(struct net *net, struct net_device *dev, bool task_vali } spin_unlock_bh(&xfrm_state_dev_gc_lock); + mutex_unlock(&xfrm_state_gc_mutex); xfrm_flush_gc(); -- 2.43.0