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[NET]: Fix module reference counts for loadable protocol modules

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I have been experimenting with loadable protocol modules, and ran into
several issues with module reference counting.

The first issue was that __module_get failed at the BUG_ON check at
the top of the routine (checking that my module reference count was
not zero) when I created the first socket. When sk_alloc() is called,
my module reference count was still 0. When I looked at why sctp
didn't have this problem, I discovered that sctp creates a control
socket during module init (when the module ref count is not 0), which
keeps the reference count non-zero. This section has been updated to
address the point Stephen raised about checking the return value of
try_module_get().

The next problem arose when my socket init routine returned an error.
This resulted in my module reference count being decremented below 0.
My socket ops->release routine was also being called. The issue here
is that sock_release() calls the ops->release routine and decrements
the ref count if sock->ops is not NULL. Since the socket probably
didn't get correctly initialized, this should not be done, so we will
set sock->ops to NULL because we will not call try_module_get().

While searching for another bug, I also noticed that sys_accept() has
a possibility of doing a module_put() when it did not do an
__module_get so I re-ordered the call to security_socket_accept().

Signed-off-by: Frank Filz <ffilzlnx@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Frank Filz
2005-09-27 15:23:38 -07:00
committed by David S. Miller
parent 9356b8fc07
commit a79af59efd
2 changed files with 20 additions and 13 deletions
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20
net/core/sock.c
View File

@@ -660,16 +660,20 @@ struct sock *sk_alloc(int family, unsigned int __nocast priority,
sock_lock_init(sk);
}
if (security_sk_alloc(sk, family, priority)) {
if (slab != NULL)
kmem_cache_free(slab, sk);
else
kfree(sk);
sk = NULL;
} else
__module_get(prot->owner);
if (security_sk_alloc(sk, family, priority))
goto out_free;
if (!try_module_get(prot->owner))
goto out_free;
}
return sk;
out_free:
if (slab != NULL)
kmem_cache_free(slab, sk);
else
kfree(sk);
return NULL;
}
void sk_free(struct sock *sk)