-stable review patch. If anyone has any objections, please let us know. ------------------ If you lose this race, it can iput a socket inode twice and you get a BUG in fs/inode.c
When I added the option for user-space to close a socket, I added some cruft to svc_delete_socket so that I could call that function when closing a socket per user-space request. This was the wrong thing to do. I should have just set SK_CLOSE and let normal mechanisms do the work. Not only wrong, but buggy. The locking is all wrong and it openned up a race where-by a socket could be closed twice. So this patch: Introduces svc_close_socket which sets SK_CLOSE then either leave the close up to a thread, or calls svc_delete_socket if it can get SK_BUSY. Adds a bias to sk_busy which is removed when SK_DEAD is set, This avoid races around shutting down the socket. Changes several 'spin_lock' to 'spin_lock_bh' where the _bh was missing. Bugzilla-url: http://bugzilla.kernel.org/show_bug.cgi?id=7916 Signed-off-by: Neil Brown <[EMAIL PROTECTED]> Signed-off-by: Greg Kroah-Hartman <[EMAIL PROTECTED]> --- include/linux/sunrpc/svcsock.h | 2 - net/sunrpc/svc.c | 4 +-- net/sunrpc/svcsock.c | 52 +++++++++++++++++++++++++++++------------ 3 files changed, 41 insertions(+), 17 deletions(-) --- linux-2.6.19.4.orig/include/linux/sunrpc/svcsock.h +++ linux-2.6.19.4/include/linux/sunrpc/svcsock.h @@ -63,7 +63,7 @@ struct svc_sock { * Function prototypes. */ int svc_makesock(struct svc_serv *, int, unsigned short); -void svc_delete_socket(struct svc_sock *); +void svc_close_socket(struct svc_sock *); int svc_recv(struct svc_rqst *, long); int svc_send(struct svc_rqst *); void svc_drop(struct svc_rqst *); --- linux-2.6.19.4.orig/net/sunrpc/svc.c +++ linux-2.6.19.4/net/sunrpc/svc.c @@ -387,7 +387,7 @@ svc_destroy(struct svc_serv *serv) svsk = list_entry(serv->sv_tempsocks.next, struct svc_sock, sk_list); - svc_delete_socket(svsk); + svc_close_socket(svsk); } if (serv->sv_shutdown) serv->sv_shutdown(serv); @@ -396,7 +396,7 @@ svc_destroy(struct svc_serv *serv) svsk = list_entry(serv->sv_permsocks.next, struct svc_sock, sk_list); - svc_delete_socket(svsk); + svc_close_socket(svsk); } cache_clean_deferred(serv); --- linux-2.6.19.4.orig/net/sunrpc/svcsock.c +++ linux-2.6.19.4/net/sunrpc/svcsock.c @@ -61,6 +61,12 @@ * after a clear, the socket must be read/accepted * if this succeeds, it must be set again. * SK_CLOSE can set at any time. It is never cleared. + * sk_inuse contains a bias of '1' until SK_DEAD is set. + * so when sk_inuse hits zero, we know the socket is dead + * and no-one is using it. + * SK_DEAD can only be set while SK_BUSY is held which ensures + * no other thread will be using the socket or will try to + * set SK_DEAD. * */ @@ -69,6 +75,7 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *, struct socket *, int *errp, int pmap_reg); +static void svc_delete_socket(struct svc_sock *svsk); static void svc_udp_data_ready(struct sock *, int); static int svc_udp_recvfrom(struct svc_rqst *); static int svc_udp_sendto(struct svc_rqst *); @@ -299,8 +306,9 @@ void svc_reserve(struct svc_rqst *rqstp, static inline void svc_sock_put(struct svc_sock *svsk) { - if (atomic_dec_and_test(&svsk->sk_inuse) && - test_bit(SK_DEAD, &svsk->sk_flags)) { + if (atomic_dec_and_test(&svsk->sk_inuse)) { + BUG_ON(! test_bit(SK_DEAD, &svsk->sk_flags)); + dprintk("svc: releasing dead socket\n"); if (svsk->sk_sock->file) sockfd_put(svsk->sk_sock); @@ -490,7 +498,7 @@ svc_sock_names(char *buf, struct svc_ser if (!serv) return 0; - spin_lock(&serv->sv_lock); + spin_lock_bh(&serv->sv_lock); list_for_each_entry(svsk, &serv->sv_permsocks, sk_list) { int onelen = one_sock_name(buf+len, svsk); if (toclose && strcmp(toclose, buf+len) == 0) @@ -498,12 +506,12 @@ svc_sock_names(char *buf, struct svc_ser else len += onelen; } - spin_unlock(&serv->sv_lock); + spin_unlock_bh(&serv->sv_lock); if (closesk) /* Should unregister with portmap, but you cannot * unregister just one protocol... */ - svc_delete_socket(closesk); + svc_close_socket(closesk); else if (toclose) return -ENOENT; return len; @@ -653,6 +661,11 @@ svc_udp_recvfrom(struct svc_rqst *rqstp) return svc_deferred_recv(rqstp); } + if (test_bit(SK_CLOSE, &svsk->sk_flags)) { + svc_delete_socket(svsk); + return 0; + } + clear_bit(SK_DATA, &svsk->sk_flags); while ((skb = skb_recv_datagram(svsk->sk_sk, 0, 1, &err)) == NULL) { if (err == -EAGAIN) { @@ -1142,7 +1155,8 @@ svc_tcp_sendto(struct svc_rqst *rqstp) rqstp->rq_sock->sk_server->sv_name, (sent<0)?"got error":"sent only", sent, xbufp->len); - svc_delete_socket(rqstp->rq_sock); + set_bit(SK_CLOSE, &rqstp->rq_sock->sk_flags); + svc_sock_enqueue(rqstp->rq_sock); sent = -EAGAIN; } return sent; @@ -1461,7 +1475,7 @@ svc_setup_socket(struct svc_serv *serv, svsk->sk_odata = inet->sk_data_ready; svsk->sk_owspace = inet->sk_write_space; svsk->sk_server = serv; - atomic_set(&svsk->sk_inuse, 0); + atomic_set(&svsk->sk_inuse, 1); svsk->sk_lastrecv = get_seconds(); spin_lock_init(&svsk->sk_defer_lock); INIT_LIST_HEAD(&svsk->sk_deferred); @@ -1582,7 +1596,7 @@ bummer: /* * Remove a dead socket */ -void +static void svc_delete_socket(struct svc_sock *svsk) { struct svc_serv *serv; @@ -1608,16 +1622,26 @@ svc_delete_socket(struct svc_sock *svsk) * while still attached to a queue, the queue itself * is about to be destroyed (in svc_destroy). */ - if (!test_and_set_bit(SK_DEAD, &svsk->sk_flags)) + if (!test_and_set_bit(SK_DEAD, &svsk->sk_flags)) { + BUG_ON(atomic_read(&svsk->sk_inuse)<2); + atomic_dec(&svsk->sk_inuse); if (test_bit(SK_TEMP, &svsk->sk_flags)) serv->sv_tmpcnt--; + } - /* This atomic_inc should be needed - svc_delete_socket - * should have the semantic of dropping a reference. - * But it doesn't yet.... - */ - atomic_inc(&svsk->sk_inuse); spin_unlock_bh(&serv->sv_lock); +} + +void svc_close_socket(struct svc_sock *svsk) +{ + set_bit(SK_CLOSE, &svsk->sk_flags); + if (test_and_set_bit(SK_BUSY, &svsk->sk_flags)) + /* someone else will have to effect the close */ + return; + + atomic_inc(&svsk->sk_inuse); + svc_delete_socket(svsk); + clear_bit(SK_BUSY, &svsk->sk_flags); svc_sock_put(svsk); } -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
