Date: Wed, 25 Nov 2015 14:45:44 +0000 (UTC) From: Fabien Thomas <fabient@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r291301 - head/sys/netinet Message-ID: <201511251445.tAPEjilx016268@repo.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: fabient Date: Wed Nov 25 14:45:43 2015 New Revision: 291301 URL: https://svnweb.freebsd.org/changeset/base/291301 Log: The r241129 description was wrong that the scenario is possible only for read locks on pcbs. The same race can happen with write lock semantics as well. The race scenario: - Two threads (1 and 2) locate pcb with writer semantics (INPLOOKUP_WLOCKPCB) and do in_pcbref() on it. - 1 and 2 both drop the inp hash lock. - Another thread (3) grabs the inp hash lock. Then it runs in_pcbfree(), which wlocks the pcb. They must happen faster than 1 or 2 come INP_WLOCK()! - 1 and 2 congest in INP_WLOCK(). - 3 does in_pcbremlists(), drops hash lock, and runs in_pcbrele_wlocked(), which doesn't free the pcb due to two references on it. Then it unlocks the pcb. - 1 (or 2) gets wlock on the pcb, runs in_pcbrele_wlocked(), which doesn't report inp as freed, due to 2 (or 1) still helding extra reference on it. The thread tries to do smth with a disconnected pcb and crashes. Submitted by: emeric.poupon@stormshield.eu Reviewed by: gleb@ MFC after: 1 week Sponsored by: Stormshield Tested by: Cassiano Peixoto, Stormshield Modified: head/sys/netinet/in_pcb.c Modified: head/sys/netinet/in_pcb.c ============================================================================== --- head/sys/netinet/in_pcb.c Wed Nov 25 13:26:42 2015 (r291300) +++ head/sys/netinet/in_pcb.c Wed Nov 25 14:45:43 2015 (r291301) @@ -1220,8 +1220,17 @@ in_pcbrele_wlocked(struct inpcb *inp) INP_WLOCK_ASSERT(inp); - if (refcount_release(&inp->inp_refcount) == 0) + if (refcount_release(&inp->inp_refcount) == 0) { + /* + * If the inpcb has been freed, let the caller know, even if + * this isn't the last reference. + */ + if (inp->inp_flags2 & INP_FREED) { + INP_WUNLOCK(inp); + return (1); + } return (0); + } KASSERT(inp->inp_socket == NULL, ("%s: inp_socket != NULL", __func__));
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201511251445.tAPEjilx016268>