Author: markj Date: Fri Apr 10 20:41:59 2020 New Revision: 359778 URL: https://svnweb.freebsd.org/changeset/base/359778
Log: Properly handle disconnected sockets in uipc_ready(). When transmitting over a unix socket, data is placed directly into the receiving socket's receive buffer, instead of the transmitting socket's send buffer. This means that when pru_ready is called during sendfile(), the passed socket does not contain M_NOTREADY mbufs in its buffers; uipc_ready() must locate the linked socket. Currently uipc_ready() frees the mbufs if the socket is disconnected, but this is wrong since the mbufs may still be present in the receiving socket's buffer after a disconnect. This can result in a use-after-free and potentially a double free if the receive buffer is flushed after uipc_ready() frees the mbufs. Fix the problem by trying harder to locate the correct socket buffer and calling sbready(): use the global list of SOCK_STREAM unix sockets to search for a sockbuf containing the now-ready mbufs. Only free the mbufs if we fail this search. Reviewed by: jah, kib Reported and tested by: pho MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D24332 Modified: head/sys/kern/uipc_usrreq.c Modified: head/sys/kern/uipc_usrreq.c ============================================================================== --- head/sys/kern/uipc_usrreq.c Fri Apr 10 18:38:42 2020 (r359777) +++ head/sys/kern/uipc_usrreq.c Fri Apr 10 20:41:59 2020 (r359778) @@ -775,6 +775,18 @@ uipc_detach(struct socket *so) vplock = NULL; local_unp_rights = 0; + SOCK_LOCK(so); + if (!SOLISTENING(so)) { + /* + * Once the socket is removed from the global lists, + * uipc_ready() will not be able to locate its socket buffer, so + * clear the buffer now. At this point internalized rights have + * already been disposed of. + */ + sbrelease(&so->so_rcv, so); + } + SOCK_UNLOCK(so); + UNP_LINK_WLOCK(); LIST_REMOVE(unp, unp_link); if (unp->unp_gcflag & UNPGC_DEAD) @@ -1244,19 +1256,54 @@ release: return (error); } +static bool +uipc_ready_scan(struct socket *so, struct mbuf *m, int count, int *errorp) +{ + struct mbuf *mb, *n; + struct sockbuf *sb; + + SOCK_LOCK(so); + if (SOLISTENING(so)) { + SOCK_UNLOCK(so); + return (false); + } + mb = NULL; + sb = &so->so_rcv; + SOCKBUF_LOCK(sb); + if (sb->sb_fnrdy != NULL) { + for (mb = sb->sb_mb, n = mb->m_nextpkt; mb != NULL;) { + if (mb == m) { + *errorp = sbready(sb, m, count); + break; + } + mb = mb->m_next; + if (mb == NULL) { + mb = n; + n = mb->m_nextpkt; + } + } + } + SOCKBUF_UNLOCK(sb); + SOCK_UNLOCK(so); + return (mb != NULL); +} + static int uipc_ready(struct socket *so, struct mbuf *m, int count) { struct unpcb *unp, *unp2; struct socket *so2; - int error; + int error, i; unp = sotounpcb(so); + KASSERT(so->so_type == SOCK_STREAM, + ("%s: unexpected socket type for %p", __func__, so)); + UNP_PCB_LOCK(unp); if ((unp2 = unp->unp_conn) == NULL) { UNP_PCB_UNLOCK(unp); - goto error; + goto search; } if (unp != unp2) { if (UNP_PCB_TRYLOCK(unp2) == 0) { @@ -1264,25 +1311,39 @@ uipc_ready(struct socket *so, struct mbuf *m, int coun UNP_PCB_UNLOCK(unp); UNP_PCB_LOCK(unp2); if (unp_pcb_rele(unp2)) - goto error; + goto search; } else UNP_PCB_UNLOCK(unp); } so2 = unp2->unp_socket; - SOCKBUF_LOCK(&so2->so_rcv); if ((error = sbready(&so2->so_rcv, m, count)) == 0) sorwakeup_locked(so2); else SOCKBUF_UNLOCK(&so2->so_rcv); - UNP_PCB_UNLOCK(unp2); + return (error); +search: + /* + * The receiving socket has been disconnected, but may still be valid. + * In this case, the now-ready mbufs are still present in its socket + * buffer, so perform an exhaustive search before giving up and freeing + * the mbufs. + */ + UNP_LINK_RLOCK(); + LIST_FOREACH(unp, &unp_shead, unp_link) { + if (uipc_ready_scan(unp->unp_socket, m, count, &error)) + break; + } + UNP_LINK_RUNLOCK(); + + if (unp == NULL) { + for (i = 0; i < count; i++) + m = m_free(m); + error = ECONNRESET; + } return (error); - error: - for (int i = 0; i < count; i++) - m = m_free(m); - return (ECONNRESET); } static int _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
