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076931989f
The following race is possible when one cpu unregisters the handler
while other one is trying to receive a message and call this one:
CPU1: CPU2:
inet_diag_rcv() inet_diag_unregister()
mutex_lock(&inet_diag_mutex);
netlink_rcv_skb(skb, &inet_diag_rcv_msg);
if (inet_diag_table[nlh->nlmsg_type] ==
NULL) /* false handler is still registered */
...
netlink_dump_start(idiagnl, skb, nlh,
inet_diag_dump, NULL);
cb = kzalloc(sizeof(*cb), GFP_KERNEL);
/* sleep here freeing memory
* or preempt
* or sleep later on nlk->cb_mutex
*/
spin_lock(&inet_diag_register_lock);
inet_diag_table[type] = NULL;
... spin_unlock(&inet_diag_register_lock);
synchronize_rcu();
/* CPU1 is sleeping - RCU quiescent
* state is passed
*/
return;
/* inet_diag_dump is finally called: */
inet_diag_dump()
handler = inet_diag_table[cb->nlh->nlmsg_type];
BUG_ON(handler == NULL);
/* OOPS! While we slept the unregister has set
* handler to NULL :(
*/
Grep showed, that the register/unregister functions are called
from init/fini module callbacks for tcp_/dccp_diag, so it's OK
to use the inet_diag_mutex to synchronize manipulations with the
inet_diag_table and the access to it.
Besides, as Herbert pointed out, asynchronous dumps should hold
this mutex as well, and thus, we provide the mutex as cb_mutex one.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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| .. | ||
| 9p | ||
| 802 | ||
| 8021q | ||
| appletalk | ||
| atm | ||
| ax25 | ||
| bluetooth | ||
| bridge | ||
| core | ||
| dccp | ||
| decnet | ||
| econet | ||
| ethernet | ||
| ieee80211 | ||
| ipv4 | ||
| ipv6 | ||
| ipx | ||
| irda | ||
| iucv | ||
| key | ||
| lapb | ||
| llc | ||
| mac80211 | ||
| netfilter | ||
| netlabel | ||
| netlink | ||
| netrom | ||
| packet | ||
| rfkill | ||
| rose | ||
| rxrpc | ||
| sched | ||
| sctp | ||
| sunrpc | ||
| tipc | ||
| unix | ||
| wanrouter | ||
| wireless | ||
| x25 | ||
| xfrm | ||
| compat.c | ||
| Kconfig | ||
| Makefile | ||
| nonet.c | ||
| socket.c | ||
| sysctl_net.c | ||
| TUNABLE | ||