From owner-dev-commits-src-branches@freebsd.org Wed Mar 31 19:56:02 2021 Return-Path: Delivered-To: dev-commits-src-branches@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 5D8925ADE16; Wed, 31 Mar 2021 19:56:02 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4F9cWQ2BXNz4Y9S; Wed, 31 Mar 2021 19:56:02 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 3A08A1F743; Wed, 31 Mar 2021 19:56:02 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.16.1/8.16.1) with ESMTP id 12VJu2Aa019211; Wed, 31 Mar 2021 19:56:02 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 12VJu2TK019210; Wed, 31 Mar 2021 19:56:02 GMT (envelope-from git) Date: Wed, 31 Mar 2021 19:56:02 GMT Message-Id: <202103311956.12VJu2TK019210@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org From: "Jonathan T. Looney" Subject: git: 40d278253d20 - releng/13.0 - Fetch the sigfastblock value in syscalls that wait for signals MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: jtl X-Git-Repository: src X-Git-Refname: refs/heads/releng/13.0 X-Git-Reftype: branch X-Git-Commit: 40d278253d205f35ec368c93b7400baddda1b81e Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-branches@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commits to the stable branches of the FreeBSD src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 31 Mar 2021 19:56:02 -0000 The branch releng/13.0 has been updated by jtl: URL: https://cgit.FreeBSD.org/src/commit/?id=40d278253d205f35ec368c93b7400baddda1b81e commit 40d278253d205f35ec368c93b7400baddda1b81e Author: Jonathan T. Looney AuthorDate: 2021-03-12 18:14:17 +0000 Commit: Jonathan T. Looney CommitDate: 2021-03-31 19:55:24 +0000 Fetch the sigfastblock value in syscalls that wait for signals We have seen several cases of processes which have become "stuck" in kern_sigsuspend(). When this occurs, the kernel's td_sigblock_val is set to 0x10 (one block outstanding) and the userspace copy of the word is set to 0 (unblocked). Because the kernel's cached value shows that signals are blocked, kern_sigsuspend() blocks almost all signals, which means the process hangs indefinitely in sigsuspend(). It is not entirely clear what is causing this condition to occur. However, it seems to make sense to add some protection against this case by fetching the latest sigfastblock value from userspace for syscalls which will sleep waiting for signals. Here, the change is applied to kern_sigsuspend() and kern_sigtimedwait(). Approved by: re (gjb) (cherry picked from commit dbec10e08808e375365fb2a2462f306e0cdfda32) (cherry picked from commit a25c17022e2d6344dcbc6192af276d2798d76d44) --- sys/kern/kern_sig.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c index 7884b5be9f91..3d55405d3151 100644 --- a/sys/kern/kern_sig.c +++ b/sys/kern/kern_sig.c @@ -1268,6 +1268,9 @@ kern_sigtimedwait(struct thread *td, sigset_t waitset, ksiginfo_t *ksi, ets.tv_nsec = 0; traced = false; + /* Ensure the sigfastblock value is up to date. */ + sigfastblock_fetch(td); + if (timeout != NULL) { if (timeout->tv_nsec >= 0 && timeout->tv_nsec < 1000000000) { timevalid = 1; @@ -1527,6 +1530,9 @@ kern_sigsuspend(struct thread *td, sigset_t mask) struct proc *p = td->td_proc; int has_sig, sig; + /* Ensure the sigfastblock value is up to date. */ + sigfastblock_fetch(td); + /* * When returning from sigsuspend, we want * the old mask to be restored after the