Date: Wed, 20 Jan 2010 11:58:04 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r202692 - in head/sys: kern sys Message-ID: <201001201158.o0KBw4oW093523@svn.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: kib Date: Wed Jan 20 11:58:04 2010 New Revision: 202692 URL: http://svn.freebsd.org/changeset/base/202692 Log: When traced process is about to receive the signal, the process is stopped and debugger may modify or drop the signal. After the changes to keep process-targeted signals on the process sigqueue, another thread may note the old signal on the queue and act before the thread removes changed or dropped signal from the process queue. Since process is traced, it usually gets stopped. Or, if the same signal is delivered while process was stopped, the thread may erronously remove it, intending to remove the original signal. Remove the signal from the queue before notifying the debugger. Restore the siginfo to the head of sigqueue when signal is allowed to be delivered to the debugee, using newly introduced KSI_HEAD ksiginfo_t flag. This preserves required order of delivery. Always restore the unchanged signal on the curthread sigqueue, not to the process queue, since the thread is about to get it anyway, because sigmask cannot be changed. Handle failure of reinserting the siginfo into the queue by falling back to sq_kill method, calling sigqueue_add with NULL ksi. If debugger changed the signal to be delivered, use sigqueue_add() with NULL ksi instead of only setting sq_signals bit. Reported by: Gardner Bell <gbell72 rogers com> Analyzed and first version of fix by: Tijl Coosemans <tijl coosemans org> PR: 142757 Reviewed by: davidxu MFC after: 2 weeks Modified: head/sys/kern/kern_sig.c head/sys/sys/signalvar.h Modified: head/sys/kern/kern_sig.c ============================================================================== --- head/sys/kern/kern_sig.c Wed Jan 20 11:55:14 2010 (r202691) +++ head/sys/kern/kern_sig.c Wed Jan 20 11:58:04 2010 (r202692) @@ -357,7 +357,10 @@ sigqueue_add(sigqueue_t *sq, int signo, /* directly insert the ksi, don't copy it */ if (si->ksi_flags & KSI_INS) { - TAILQ_INSERT_TAIL(&sq->sq_list, si, ksi_link); + if (si->ksi_flags & KSI_HEAD) + TAILQ_INSERT_HEAD(&sq->sq_list, si, ksi_link); + else + TAILQ_INSERT_TAIL(&sq->sq_list, si, ksi_link); si->ksi_sigq = sq; goto out_set_bit; } @@ -378,7 +381,10 @@ sigqueue_add(sigqueue_t *sq, int signo, p->p_pendingcnt++; ksiginfo_copy(si, ksi); ksi->ksi_signo = signo; - TAILQ_INSERT_TAIL(&sq->sq_list, ksi, ksi_link); + if (si->ksi_flags & KSI_HEAD) + TAILQ_INSERT_HEAD(&sq->sq_list, ksi, ksi_link); + else + TAILQ_INSERT_TAIL(&sq->sq_list, ksi, ksi_link); ksi->ksi_sigq = sq; } @@ -2492,6 +2498,7 @@ issignal(struct thread *td, int stop_all struct sigacts *ps; struct sigqueue *queue; sigset_t sigpending; + ksiginfo_t ksi; int sig, prop, newsig; p = td->td_proc; @@ -2529,24 +2536,22 @@ issignal(struct thread *td, int stop_all if (p->p_flag & P_TRACED && (p->p_flag & P_PPWAIT) == 0) { /* * If traced, always stop. + * Remove old signal from queue before the stop. + * XXX shrug off debugger, it causes siginfo to + * be thrown away. */ + queue = &td->td_sigqueue; + ksi.ksi_signo = 0; + if (sigqueue_get(queue, sig, &ksi) == 0) { + queue = &p->p_sigqueue; + sigqueue_get(queue, sig, &ksi); + } + mtx_unlock(&ps->ps_mtx); newsig = ptracestop(td, sig); mtx_lock(&ps->ps_mtx); if (sig != newsig) { - ksiginfo_t ksi; - - queue = &td->td_sigqueue; - /* - * clear old signal. - * XXX shrug off debugger, it causes siginfo to - * be thrown away. - */ - if (sigqueue_get(queue, sig, &ksi) == 0) { - queue = &p->p_sigqueue; - sigqueue_get(queue, sig, &ksi); - } /* * If parent wants us to take the signal, @@ -2561,10 +2566,20 @@ issignal(struct thread *td, int stop_all * Put the new signal into td_sigqueue. If the * signal is being masked, look for other signals. */ - SIGADDSET(queue->sq_signals, sig); + sigqueue_add(queue, sig, NULL); if (SIGISMEMBER(td->td_sigmask, sig)) continue; signotify(td); + } else { + if (ksi.ksi_signo != 0) { + ksi.ksi_flags |= KSI_HEAD; + if (sigqueue_add(&td->td_sigqueue, sig, + &ksi) != 0) + ksi.ksi_signo = 0; + } + if (ksi.ksi_signo == 0) + sigqueue_add(&td->td_sigqueue, sig, + NULL); } /* Modified: head/sys/sys/signalvar.h ============================================================================== --- head/sys/sys/signalvar.h Wed Jan 20 11:55:14 2010 (r202691) +++ head/sys/sys/signalvar.h Wed Jan 20 11:58:04 2010 (r202692) @@ -234,6 +234,7 @@ typedef struct ksiginfo { #define KSI_EXT 0x02 /* Externally managed ksi. */ #define KSI_INS 0x04 /* Directly insert ksi, not the copy */ #define KSI_SIGQ 0x08 /* Generated by sigqueue, might ret EGAIN. */ +#define KSI_HEAD 0x10 /* Insert into head, not tail. */ #define KSI_COPYMASK (KSI_TRAP|KSI_SIGQ) #define KSI_ONQ(ksi) ((ksi)->ksi_sigq != NULL)
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201001201158.o0KBw4oW093523>