234ec0b603
I analyze the potential sleeping issue of the following processes:
Thread A Thread B
... netlink_create //ref = 1
do_mq_notify ...
sock = netlink_getsockbyfilp ... //ref = 2
info->notify_sock = sock; ...
... netlink_sendmsg
... skb = netlink_alloc_large_skb //skb->head is vmalloced
... netlink_unicast
... sk = netlink_getsockbyportid //ref = 3
... netlink_sendskb
... __netlink_sendskb
... skb_queue_tail //put skb to sk_receive_queue
... sock_put //ref = 2
... ...
... netlink_release
... deferred_put_nlk_sk //ref = 1
mqueue_flush_file
spin_lock
remove_notification
netlink_sendskb
sock_put //ref = 0
sk_free
...
__sk_destruct
netlink_sock_destruct
skb_queue_purge //get skb from sk_receive_queue
...
__skb_queue_purge_reason
kfree_skb_reason
__kfree_skb
...
skb_release_all
skb_release_head_state
netlink_skb_destructor
vfree(skb->head) //sleeping while holding spinlock
In netlink_sendmsg, if the memory pointed to by skb->head is allocated by
vmalloc, and is put to sk_receive_queue queue, also the skb is not freed.
When the mqueue executes flush, the sleeping bug will occur. Use
vfree_atomic instead of vfree in netlink_skb_destructor to solve the issue.
Fixes:
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|---|---|---|
| .. | ||
| Kconfig | ||
| Makefile | ||
| af_netlink.c | ||
| af_netlink.h | ||
| diag.c | ||
| genetlink.c | ||
| policy.c | ||