The branch stable/15 has been updated by tuexen: URL: https://cgit.FreeBSD.org/src/commit/?id=9611bf2fed71ca62161249630f98e7eac06eff6b
commit 9611bf2fed71ca62161249630f98e7eac06eff6b Author: Michael Tuexen <[email protected]> AuthorDate: 2025-10-27 22:28:59 +0000 Commit: Michael Tuexen <[email protected]> CommitDate: 2025-10-29 09:09:51 +0000 tcp: improve credential handling in syncache When adding a syncache entry, take a reference count of the credentials while the inp is still locked. Thanks to markj@ for providing a hint regarding the root cause. Reported by: David Marker Reviewed by: glebius Tested by: David Marker Fixes: cbc9438f0505 ("tcp: improve ref count handling when processing SYN") Sponsored by: Netflix, Inc. Differential Revision: https://reviews.freebsd.org/D53380 (cherry picked from commit 44cb1e857f048d2326bdc1a032ccd2c04d2bcdc9) --- sys/netinet/tcp_syncache.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/sys/netinet/tcp_syncache.c b/sys/netinet/tcp_syncache.c index 3cb538f7054d..3a7755e9f09e 100644 --- a/sys/netinet/tcp_syncache.c +++ b/sys/netinet/tcp_syncache.c @@ -1380,6 +1380,7 @@ syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, struct tcpcb *tp; struct socket *rv = NULL; struct syncache *sc = NULL; + struct ucred *cred; struct syncache_head *sch; struct mbuf *ipopts = NULL; u_int ltflags; @@ -1408,6 +1409,7 @@ syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, */ KASSERT(SOLISTENING(so), ("%s: %p not listening", __func__, so)); tp = sototcpcb(so); + cred = V_tcp_syncache.see_other ? NULL : crhold(so->so_cred); #ifdef INET6 if (inc->inc_flags & INC_ISIPV6) { @@ -1636,16 +1638,16 @@ syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, /* * sc_cred is only used in syncache_pcblist() to list TCP endpoints in * TCPS_SYN_RECEIVED state when V_tcp_syncache.see_other is false. - * Therefore, store the credentials and take a reference count only - * when needed: + * Therefore, store the credentials only when needed: * - sc is allocated from the zone and not using the on stack instance. * - the sysctl variable net.inet.tcp.syncache.see_other is false. * The reference count is decremented when a zone allocated sc is * freed in syncache_free(). */ - if (sc != &scs && !V_tcp_syncache.see_other) - sc->sc_cred = crhold(so->so_cred); - else + if (sc != &scs && !V_tcp_syncache.see_other) { + sc->sc_cred = cred; + cred = NULL; + } else sc->sc_cred = NULL; sc->sc_port = port; sc->sc_ipopts = ipopts; @@ -1783,6 +1785,8 @@ donenoprobe: tcp_fastopen_decrement_counter(tfo_pending); tfo_expanded: + if (cred != NULL) + crfree(cred); if (sc == NULL || sc == &scs) { #ifdef MAC mac_syncache_destroy(&maclabel);
