From owner-svn-src-head@freebsd.org Sat Jan 9 01:56:47 2016 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id AAA46A67D45; Sat, 9 Jan 2016 01:56:47 +0000 (UTC) (envelope-from markj@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 6E5D0139A; Sat, 9 Jan 2016 01:56:47 +0000 (UTC) (envelope-from markj@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id u091ukur069963; Sat, 9 Jan 2016 01:56:46 GMT (envelope-from markj@FreeBSD.org) Received: (from markj@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id u091ukMo069962; Sat, 9 Jan 2016 01:56:46 GMT (envelope-from markj@FreeBSD.org) Message-Id: <201601090156.u091ukMo069962@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: markj set sender to markj@FreeBSD.org using -f From: Mark Johnston Date: Sat, 9 Jan 2016 01:56:46 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r293458 - head/sys/kern X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 09 Jan 2016 01:56:47 -0000 Author: markj Date: Sat Jan 9 01:56:46 2016 New Revision: 293458 URL: https://svnweb.freebsd.org/changeset/base/293458 Log: Prevent cv_waiters wraparound. r282971 attempted to fix this problem by decrementing cv_waiters after waking up from sleeping on a condition variable, but this can result in a use-after-free if the CV is freed before all woken threads have had a chance to run. Instead, avoid incrementing cv_waiters past INT_MAX, and have cv_signal() explicitly check for sleeping threads once cv_waiters has reached this bound. Reviewed by: jhb MFC after: 2 weeks Sponsored by: EMC / Isilon Storage Division Differential Revision: https://reviews.freebsd.org/D4822 Modified: head/sys/kern/kern_condvar.c Modified: head/sys/kern/kern_condvar.c ============================================================================== --- head/sys/kern/kern_condvar.c Sat Jan 9 01:43:53 2016 (r293457) +++ head/sys/kern/kern_condvar.c Sat Jan 9 01:56:46 2016 (r293458) @@ -31,6 +31,7 @@ __FBSDID("$FreeBSD$"); #include #include +#include #include #include #include @@ -47,6 +48,17 @@ __FBSDID("$FreeBSD$"); #endif /* + * A bound below which cv_waiters is valid. Once cv_waiters reaches this bound, + * cv_signal must manually check the wait queue for threads. + */ +#define CV_WAITERS_BOUND INT_MAX + +#define CV_WAITERS_INC(cvp) do { \ + if ((cvp)->cv_waiters < CV_WAITERS_BOUND) \ + (cvp)->cv_waiters++; \ +} while (0) + +/* * Common sanity checks for cv_wait* functions. */ #define CV_ASSERT(cvp, lock, td) do { \ @@ -122,7 +134,7 @@ _cv_wait(struct cv *cvp, struct lock_obj sleepq_lock(cvp); - cvp->cv_waiters++; + CV_WAITERS_INC(cvp); if (lock == &Giant.lock_object) mtx_assert(&Giant, MA_OWNED); DROP_GIANT(); @@ -184,7 +196,7 @@ _cv_wait_unlock(struct cv *cvp, struct l sleepq_lock(cvp); - cvp->cv_waiters++; + CV_WAITERS_INC(cvp); DROP_GIANT(); sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0); @@ -240,7 +252,7 @@ _cv_wait_sig(struct cv *cvp, struct lock sleepq_lock(cvp); - cvp->cv_waiters++; + CV_WAITERS_INC(cvp); if (lock == &Giant.lock_object) mtx_assert(&Giant, MA_OWNED); DROP_GIANT(); @@ -307,7 +319,7 @@ _cv_timedwait_sbt(struct cv *cvp, struct sleepq_lock(cvp); - cvp->cv_waiters++; + CV_WAITERS_INC(cvp); if (lock == &Giant.lock_object) mtx_assert(&Giant, MA_OWNED); DROP_GIANT(); @@ -376,7 +388,7 @@ _cv_timedwait_sig_sbt(struct cv *cvp, st sleepq_lock(cvp); - cvp->cv_waiters++; + CV_WAITERS_INC(cvp); if (lock == &Giant.lock_object) mtx_assert(&Giant, MA_OWNED); DROP_GIANT(); @@ -422,8 +434,15 @@ cv_signal(struct cv *cvp) wakeup_swapper = 0; sleepq_lock(cvp); if (cvp->cv_waiters > 0) { - cvp->cv_waiters--; - wakeup_swapper = sleepq_signal(cvp, SLEEPQ_CONDVAR, 0, 0); + if (cvp->cv_waiters == CV_WAITERS_BOUND && + sleepq_lookup(cvp) == NULL) { + cvp->cv_waiters = 0; + } else { + if (cvp->cv_waiters < CV_WAITERS_BOUND) + cvp->cv_waiters--; + wakeup_swapper = sleepq_signal(cvp, SLEEPQ_CONDVAR, 0, + 0); + } } sleepq_release(cvp); if (wakeup_swapper)