The following reply was made to PR kern/172963; it has been noted by GNATS.
From: [email protected] (dfilter service) To: [email protected] Cc: Subject: Re: kern/172963: commit references a PR Date: Sun, 14 Apr 2013 16:26:17 +0000 (UTC) Author: rwatson Date: Sun Apr 14 16:25:37 2013 New Revision: 249478 URL: http://svnweb.freebsd.org/changeset/base/249478 Log: FreeBSD 8.0 introduced inpcb reference counting, and FreeBSD 8.1 began using that reference count to protect inpcb stability in udp_pcblist() and other monitoring functions, preventing the inpcb from being garbage collected across potentially sleeping copyout() operations despite the inpcb zone becoming shrinkable. However, this introduced a race condition in which inp->inp_socket() might become NULL as a result of the socket being freed, but before the inpcb we removed from the global list of connections, allowing it to be exposed to a third thread invoking udp_input() or udp6_input() which would try to indirect through inp_socket without testing it for NULL. This might occur with particular regularity on systems that frequently run netstat, or which use SNMP for connection monitoring. Later FreeBSD releases use a different reference/destruction model, but stable/8 remained affected in FreeBSD 8.2 and 8.3; the problem could be spotted on very high-load UDP services, such as top-level name servers. An Errata Note for 8.x branches under continuing support might be appropriate. Regardless, this fix should be merged to releng/8.4 prior to 8.4-RELEASE. PR: 172963 Submitted by: Vincent Miller <[email protected]> Submitted by: Julien Charbon <[email protected]> Submitted by: Marc De La Gueronniere <[email protected]> Modified: stable/8/sys/netinet/udp_usrreq.c stable/8/sys/netinet6/udp6_usrreq.c Modified: stable/8/sys/netinet/udp_usrreq.c ============================================================================== --- stable/8/sys/netinet/udp_usrreq.c Sun Apr 14 16:20:25 2013 (r249477) +++ stable/8/sys/netinet/udp_usrreq.c Sun Apr 14 16:25:37 2013 (r249478) @@ -495,6 +495,15 @@ udp_input(struct mbuf *m, int off) INP_RLOCK(inp); /* + * Detached PCBs can linger in the list if someone + * holds a reference. (e.g. udp_pcblist) + */ + if (inp->inp_socket == NULL) { + INP_RUNLOCK(inp); + continue; + } + + /* * Handle socket delivery policy for any-source * and source-specific multicast. [RFC3678] */ @@ -620,6 +629,15 @@ udp_input(struct mbuf *m, int off) */ INP_RLOCK(inp); INP_INFO_RUNLOCK(&V_udbinfo); + + /* + * Detached PCBs can linger in the hash table if someone holds a + * reference. (e.g. udp_pcblist) + */ + if (inp->inp_socket == NULL) { + INP_RUNLOCK(inp); + goto badunlocked; + } if (inp->inp_ip_minttl && inp->inp_ip_minttl > ip->ip_ttl) { INP_RUNLOCK(inp); goto badunlocked; Modified: stable/8/sys/netinet6/udp6_usrreq.c ============================================================================== --- stable/8/sys/netinet6/udp6_usrreq.c Sun Apr 14 16:20:25 2013 (r249477) +++ stable/8/sys/netinet6/udp6_usrreq.c Sun Apr 14 16:25:37 2013 (r249478) @@ -273,6 +273,13 @@ udp6_input(struct mbuf **mp, int *offp, } /* + * Detached PCBs can linger in the list if someone + * holds a reference. (e.g. udp_pcblist) + */ + if (inp->inp_socket == NULL) + continue; + + /* * Handle socket delivery policy for any-source * and source-specific multicast. [RFC3678] */ @@ -396,6 +403,15 @@ udp6_input(struct mbuf **mp, int *offp, } INP_RLOCK(inp); INP_INFO_RUNLOCK(&V_udbinfo); + + /* + * Detached PCBs can linger in the hash table if someone holds a + * reference. (e.g. udp_pcblist) + */ + if (inp->inp_socket == NULL) { + INP_RUNLOCK(inp); + goto badunlocked; + } up = intoudpcb(inp); if (up->u_tun_func == NULL) { udp6_append(inp, m, off, &fromsa); _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "[email protected]" _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "[email protected]"
