e3d3e8289b
This unreliably breaks libc handling of vfork where forking succeded, but execve did not. vfork code in libc performs waitpid with WNOHANG in case of failed exec. With the fix exit codepath was waking up the parent before the child fully transitioned to a zombie. Woken up parent would waitpid, which could find a not-yet-zombie child and fail to reap it due to the WNOHANG flag. While removing the flag fixes the problem, it is not an option due to older releases which would still suffer from the kernel change. Revert the fix until a solution can be worked out. Note that while use-after-free which gets back due to the revert is a real bug, it's side-effects are limited due to the fact that struct proc memory is never released by UMA.
271 lines
7.7 KiB
C
271 lines
7.7 KiB
C
/*-
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* SPDX-License-Identifier: BSD-4-Clause
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*
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* Copyright (C) 1994, David Greenman
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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* Copyright (C) 2010 Konstantin Belousov <kib@freebsd.org>
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*
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* This code is derived from software contributed to Berkeley by
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* the University of Utah, and William Jolitz.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: @(#)trap.c 7.4 (Berkeley) 5/13/91
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*/
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#include "opt_capsicum.h"
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#include "opt_ktrace.h"
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__FBSDID("$FreeBSD$");
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#include <sys/capsicum.h>
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#include <sys/ktr.h>
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#include <sys/vmmeter.h>
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#ifdef KTRACE
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#include <sys/uio.h>
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#include <sys/ktrace.h>
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#endif
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#include <security/audit/audit.h>
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static inline int
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syscallenter(struct thread *td)
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{
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struct proc *p;
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struct syscall_args *sa;
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int error, traced;
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VM_CNT_INC(v_syscall);
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p = td->td_proc;
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sa = &td->td_sa;
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td->td_pticks = 0;
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if (td->td_cowgen != p->p_cowgen)
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thread_cow_update(td);
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traced = (p->p_flag & P_TRACED) != 0;
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if (traced || td->td_dbgflags & TDB_USERWR) {
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PROC_LOCK(p);
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td->td_dbgflags &= ~TDB_USERWR;
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if (traced)
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td->td_dbgflags |= TDB_SCE;
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PROC_UNLOCK(p);
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}
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error = (p->p_sysent->sv_fetch_syscall_args)(td);
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_SYSCALL))
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ktrsyscall(sa->code, sa->narg, sa->args);
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#endif
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KTR_START4(KTR_SYSC, "syscall", syscallname(p, sa->code),
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(uintptr_t)td, "pid:%d", td->td_proc->p_pid, "arg0:%p", sa->args[0],
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"arg1:%p", sa->args[1], "arg2:%p", sa->args[2]);
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if (error == 0) {
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STOPEVENT(p, S_SCE, sa->narg);
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if (p->p_flag & P_TRACED) {
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PROC_LOCK(p);
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if (p->p_ptevents & PTRACE_SCE)
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ptracestop((td), SIGTRAP, NULL);
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PROC_UNLOCK(p);
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}
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if (td->td_dbgflags & TDB_USERWR) {
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/*
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* Reread syscall number and arguments if
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* debugger modified registers or memory.
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*/
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error = (p->p_sysent->sv_fetch_syscall_args)(td);
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_SYSCALL))
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ktrsyscall(sa->code, sa->narg, sa->args);
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#endif
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if (error != 0)
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goto retval;
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}
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#ifdef CAPABILITY_MODE
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/*
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* In capability mode, we only allow access to system calls
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* flagged with SYF_CAPENABLED.
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*/
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if (IN_CAPABILITY_MODE(td) &&
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!(sa->callp->sy_flags & SYF_CAPENABLED)) {
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error = ECAPMODE;
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goto retval;
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}
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#endif
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error = syscall_thread_enter(td, sa->callp);
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if (error != 0)
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goto retval;
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#ifdef KDTRACE_HOOKS
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/* Give the syscall:::entry DTrace probe a chance to fire. */
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if (__predict_false(systrace_enabled &&
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sa->callp->sy_entry != 0))
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(*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0);
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#endif
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AUDIT_SYSCALL_ENTER(sa->code, td);
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error = (sa->callp->sy_call)(td, sa->args);
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AUDIT_SYSCALL_EXIT(error, td);
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/* Save the latest error return value. */
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if ((td->td_pflags & TDP_NERRNO) == 0)
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td->td_errno = error;
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#ifdef KDTRACE_HOOKS
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/* Give the syscall:::return DTrace probe a chance to fire. */
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if (__predict_false(systrace_enabled &&
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sa->callp->sy_return != 0))
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(*systrace_probe_func)(sa, SYSTRACE_RETURN,
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error ? -1 : td->td_retval[0]);
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#endif
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syscall_thread_exit(td, sa->callp);
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}
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retval:
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KTR_STOP4(KTR_SYSC, "syscall", syscallname(p, sa->code),
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(uintptr_t)td, "pid:%d", td->td_proc->p_pid, "error:%d", error,
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"retval0:%#lx", td->td_retval[0], "retval1:%#lx",
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td->td_retval[1]);
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if (traced) {
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PROC_LOCK(p);
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td->td_dbgflags &= ~TDB_SCE;
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PROC_UNLOCK(p);
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}
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(p->p_sysent->sv_set_syscall_retval)(td, error);
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return (error);
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}
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static inline void
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syscallret(struct thread *td, int error)
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{
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struct proc *p, *p2;
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struct syscall_args *sa;
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ksiginfo_t ksi;
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int traced, error1;
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KASSERT((td->td_pflags & TDP_FORKING) == 0,
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("fork() did not clear TDP_FORKING upon completion"));
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p = td->td_proc;
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sa = &td->td_sa;
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if ((trap_enotcap || (p->p_flag2 & P2_TRAPCAP) != 0) &&
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IN_CAPABILITY_MODE(td)) {
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error1 = (td->td_pflags & TDP_NERRNO) == 0 ? error :
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td->td_errno;
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if (error1 == ENOTCAPABLE || error1 == ECAPMODE) {
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ksiginfo_init_trap(&ksi);
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ksi.ksi_signo = SIGTRAP;
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ksi.ksi_errno = error1;
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ksi.ksi_code = TRAP_CAP;
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trapsignal(td, &ksi);
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}
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}
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/*
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* Handle reschedule and other end-of-syscall issues
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*/
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userret(td, td->td_frame);
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_SYSRET)) {
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ktrsysret(sa->code, (td->td_pflags & TDP_NERRNO) == 0 ?
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error : td->td_errno, td->td_retval[0]);
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}
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#endif
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td->td_pflags &= ~TDP_NERRNO;
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if (p->p_flag & P_TRACED) {
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traced = 1;
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PROC_LOCK(p);
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td->td_dbgflags |= TDB_SCX;
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PROC_UNLOCK(p);
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} else
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traced = 0;
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/*
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* This works because errno is findable through the
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* register set. If we ever support an emulation where this
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* is not the case, this code will need to be revisited.
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*/
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STOPEVENT(p, S_SCX, sa->code);
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if (traced || (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0) {
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PROC_LOCK(p);
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/*
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* If tracing the execed process, trap to the debugger
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* so that breakpoints can be set before the program
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* executes. If debugger requested tracing of syscall
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* returns, do it now too.
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*/
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if (traced &&
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((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
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(p->p_ptevents & PTRACE_SCX) != 0))
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ptracestop(td, SIGTRAP, NULL);
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td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
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PROC_UNLOCK(p);
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}
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if (__predict_false(td->td_pflags & TDP_RFPPWAIT)) {
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/*
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* Preserve synchronization semantics of vfork. If
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* waiting for child to exec or exit, fork set
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* P_PPWAIT on child, and there we sleep on our proc
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* (in case of exit).
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*
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* Do it after the ptracestop() above is finished, to
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* not block our debugger until child execs or exits
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* to finish vfork wait.
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*/
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td->td_pflags &= ~TDP_RFPPWAIT;
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p2 = td->td_rfppwait_p;
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again:
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PROC_LOCK(p2);
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while (p2->p_flag & P_PPWAIT) {
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PROC_LOCK(p);
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if (thread_suspend_check_needed()) {
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PROC_UNLOCK(p2);
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thread_suspend_check(0);
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PROC_UNLOCK(p);
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goto again;
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} else {
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PROC_UNLOCK(p);
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}
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cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz);
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}
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PROC_UNLOCK(p2);
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if (td->td_dbgflags & TDB_VFORK) {
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PROC_LOCK(p);
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if (p->p_ptevents & PTRACE_VFORK)
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ptracestop(td, SIGTRAP, NULL);
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td->td_dbgflags &= ~TDB_VFORK;
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PROC_UNLOCK(p);
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}
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}
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}
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