Messages in this thread Patch in this message | | | Date | Thu, 26 Dec 2002 00:11:43 -0800 (PST) | From | Max Krasnyansky <> | Subject | Re: [PATCH/RFC] New module refcounting for net_proto_family |
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> Bunch of problems with this patch: > > 1) Module leak. If try_module_get(npf->owner) works but sock_alloc() > fails, we never put the module. It just branches to the "out" > label in that case, which unlocks the net_family table and returns > err. Yeah, I missed that one. Fixed in the new patch.
> 2) Bigger issue, why not attach the owner to struct sock > instead of socket? The sock can exist, and thus reference > the protocol family code, long after the socket (ie. the > user end) is killed off and closed. > > For example, this could happen for just about any protocol family > due to stray device sk_buff references to the sock and thus the > protocol family. Good point. Alghough generic socket code does not necessarily reference proto family module via struct sock. Only in case when family installed non default callbacks (sk->dataready, sk->destruct, etc). Some families (af_ipx for example) don't. But I think it's a good idea to refcount struct sock anyway.
Ok. Here is the new patch. We still need owner field in struct socket.
# This is a BitKeeper generated patch for the following project: # Project Name: Linux kernel tree # This patch format is intended for GNU patch command version 2.5 or higher. # This patch includes the following deltas: # ChangeSet 1.889 -> 1.890 # net/socket.c 1.39 -> 1.40 # include/linux/net.h 1.7 -> 1.8 # include/net/sock.h 1.29 -> 1.30 # net/core/sock.c 1.14 -> 1.15 # # The following is the BitKeeper ChangeSet Log # -------------------------------------------- # 02/12/25 maxk@qualcomm.com 1.890 # Convert generic socket code to the new module refcounting API. # -------------------------------------------- # diff -Nru a/include/linux/net.h b/include/linux/net.h --- a/include/linux/net.h Wed Dec 25 23:29:28 2002 +++ b/include/linux/net.h Wed Dec 25 23:29:28 2002 @@ -76,6 +76,8 @@ short type; unsigned char passcred; + + struct module *owner; }; struct scm_cookie; @@ -124,6 +126,8 @@ short authentication; short encryption; short encrypt_net; + + struct module *owner; }; struct net_proto diff -Nru a/include/net/sock.h b/include/net/sock.h --- a/include/net/sock.h Wed Dec 25 23:29:28 2002 +++ b/include/net/sock.h Wed Dec 25 23:29:28 2002 @@ -41,6 +41,7 @@ #include <linux/config.h> #include <linux/timer.h> #include <linux/cache.h> +#include <linux/module.h> #include <linux/netdevice.h> #include <linux/skbuff.h> /* struct sk_buff */ @@ -196,7 +197,9 @@ /* RPC layer private data */ void *user_data; - + + struct module *owner; + /* Callbacks */ void (*state_change)(struct sock *sk); void (*data_ready)(struct sock *sk,int bytes); @@ -577,6 +580,9 @@ static inline void sock_graft(struct sock *sk, struct socket *parent) { + try_module_get(parent->owner); + sk->owner = parent->owner; + write_lock_bh(&sk->callback_lock); sk->sleep = &parent->wait; parent->sk = sk; diff -Nru a/net/core/sock.c b/net/core/sock.c --- a/net/core/sock.c Wed Dec 25 23:29:28 2002 +++ b/net/core/sock.c Wed Dec 25 23:29:28 2002 @@ -601,6 +601,7 @@ sock_lock_init(sk); } sk->slab = slab; + sk->owner = NULL; } return sk; @@ -626,6 +627,8 @@ if (atomic_read(&sk->omem_alloc)) printk(KERN_DEBUG "sk_free: optmem leakage (%d bytes) detected.\n", atomic_read(&sk->omem_alloc)); + module_put(sk->owner); + kmem_cache_free(sk->slab, sk); } @@ -1084,10 +1087,10 @@ sk->zapped = 1; sk->socket = sock; - if(sock) - { + if (sock) { sk->type = sock->type; sk->sleep = &sock->wait; + sk->owner = sock->owner; sock->sk = sk; } else sk->sleep = NULL; diff -Nru a/net/socket.c b/net/socket.c --- a/net/socket.c Wed Dec 25 23:29:28 2002 +++ b/net/socket.c Wed Dec 25 23:29:28 2002 @@ -470,6 +470,8 @@ sock = SOCKET_I(inode); + sock->owner = NULL; + inode->i_mode = S_IFSOCK|S_IRWXUGO; inode->i_sock = 1; inode->i_uid = current->fsuid; @@ -964,8 +966,9 @@ int sock_create(int family, int type, int protocol, struct socket **res) { - int i; + struct net_proto_family *npf; struct socket *sock; + int err; /* * Check protocol is in range @@ -990,14 +993,8 @@ } #if defined(CONFIG_KMOD) && defined(CONFIG_NET) - /* Attempt to load a protocol module if the find failed. - * - * 12/09/1996 Marcin: But! this makes REALLY only sense, if the user - * requested real, full-featured networking support upon configuration. - * Otherwise module support will break! - */ - if (net_families[family]==NULL) - { + /* Attempt to load a protocol module if the find failed. */ + if (net_families[family]==NULL) { char module_name[30]; sprintf(module_name,"net-pf-%d",family); request_module(module_name); @@ -1005,29 +1002,31 @@ #endif net_family_read_lock(); - if (net_families[family] == NULL) { - i = -EAFNOSUPPORT; - goto out; - } -/* - * Allocate the socket and allow the family to set things up. if - * the protocol is 0, the family is instructed to select an appropriate - * default. - */ + npf = net_families[family]; + if (!npf || !try_module_get(npf->owner)) { + net_family_read_unlock(); + return -EAFNOSUPPORT; + } + + /* + * Allocate the socket and allow the family to set things up. if + * the protocol is 0, the family is instructed to select an appropriate + * default. + */ - if (!(sock = sock_alloc())) - { + sock = sock_alloc(); + if (!sock) { printk(KERN_WARNING "socket: no more sockets\n"); - i = -ENFILE; /* Not exactly a match, but its the + err = -ENFILE; /* Not exactly a match, but its the closest posix thing */ goto out; } sock->type = type; + sock->owner = npf->owner; - if ((i = net_families[family]->create(sock, protocol)) < 0) - { + if ((err = npf->create(sock, protocol)) < 0) { sock_release(sock); goto out; } @@ -1036,7 +1035,9 @@ out: net_family_read_unlock(); - return i; + if (err) + module_put(npf->owner); + return err; } asmlinkage long sys_socket(int family, int type, int protocol) @@ -1198,9 +1199,10 @@ if (!(newsock = sock_alloc())) goto out_put; - newsock->type = sock->type; - newsock->ops = sock->ops; - + newsock->type = sock->type; + newsock->ops = sock->ops; + newsock->owner = sock->owner; + err = sock->ops->accept(sock, newsock, sock->file->f_flags); if (err < 0) goto out_release; --
Max
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