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netlink: add reference of module in netlink_dump_start 

I get a panic when I use ss -a and rmmod inet_diag at the
same time.

It's because netlink_dump uses inet_diag_dump which belongs to module
inet_diag.

I search the codes and find many modules have the same problem.  We
need to add a reference to the module which the cb->dump belongs to.

Thanks for all help from Stephen,Jan,Eric,Steffen and Pablo.

Change From v3:
change netlink_dump_start to inline,suggestion from Pablo and
Eric.

Change From v2:
delete netlink_dump_done,and call module_put in netlink_dump
and netlink_sock_destruct.

Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gao feng 2012-10-04 20:15:48 +00:00 committed by David S. Miller
parent ed5062ddaa
commit 6dc878a8ca
2 changed files with 37 additions and 12 deletions
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20
include/linux/netlink.h
View File

@ -245,6 +245,8 @@ struct netlink_callback {
struct netlink_callback *cb);
int (*done)(struct netlink_callback *cb);
void *data;
/* the module that dump function belong to */
struct module *module;
u16 family;
u16 min_dump_alloc;
unsigned int prev_seq, seq;
@ -262,14 +264,24 @@ __nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int fla
struct netlink_dump_control {
int (*dump)(struct sk_buff *skb, struct netlink_callback *);
int (*done)(struct netlink_callback*);
int (*done)(struct netlink_callback *);
void *data;
struct module *module;
u16 min_dump_alloc;
};
extern int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
const struct nlmsghdr *nlh,
struct netlink_dump_control *control);
extern int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
const struct nlmsghdr *nlh,
struct netlink_dump_control *control);
static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
const struct nlmsghdr *nlh,
struct netlink_dump_control *control)
{
if (!control->module)
control->module = THIS_MODULE;
return __netlink_dump_start(ssk, skb, nlh, control);
}
#endif /* __KERNEL__ */

29
net/netlink/af_netlink.c
View File

@ -169,6 +169,8 @@ static void netlink_sock_destruct(struct sock *sk)
if (nlk->cb) {
if (nlk->cb->done)
nlk->cb->done(nlk->cb);
module_put(nlk->cb->module);
netlink_destroy_callback(nlk->cb);
}
@ -1758,6 +1760,7 @@ static int netlink_dump(struct sock *sk)
nlk->cb = NULL;
mutex_unlock(nlk->cb_mutex);
module_put(cb->module);
netlink_consume_callback(cb);
return 0;
@ -1767,9 +1770,9 @@ errout_skb:
return err;
}
int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
const struct nlmsghdr *nlh,
struct netlink_dump_control *control)
int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
const struct nlmsghdr *nlh,
struct netlink_dump_control *control)
{
struct netlink_callback *cb;
struct sock *sk;
@ -1784,6 +1787,7 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
cb->done = control->done;
cb->nlh = nlh;
cb->data = control->data;
cb->module = control->module;
cb->min_dump_alloc = control->min_dump_alloc;
atomic_inc(&skb->users);
cb->skb = skb;
@ -1794,19 +1798,28 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
return -ECONNREFUSED;
}
nlk = nlk_sk(sk);
/* A dump is in progress... */
mutex_lock(nlk->cb_mutex);
/* A dump is in progress... */
if (nlk->cb) {
mutex_unlock(nlk->cb_mutex);
netlink_destroy_callback(cb);
sock_put(sk);
return -EBUSY;
ret = -EBUSY;
goto out;
}
/* add reference of module which cb->dump belongs to */
if (!try_module_get(cb->module)) {
mutex_unlock(nlk->cb_mutex);
netlink_destroy_callback(cb);
ret = -EPROTONOSUPPORT;
goto out;
}
nlk->cb = cb;
mutex_unlock(nlk->cb_mutex);
ret = netlink_dump(sk);
out:
sock_put(sk);
if (ret)
@ -1817,7 +1830,7 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
*/
return -EINTR;
}
EXPORT_SYMBOL(netlink_dump_start);
EXPORT_SYMBOL(__netlink_dump_start);
void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
{