svn commit: r352181 - in stable/12: sys/kern tests/sys/kern

[Mariusz Zaborski]

Author: oshogbo
Date: Tue Sep 10 20:18:06 2019
New Revision: 352181
URL: https://svnweb.freebsd.org/changeset/base/352181

Log:
  MFCr350612
    procdesc: fix reparenting when the debugger is attached
  
    The process is reparented to the debugger while it is attached.
      B          B
     /   ---->   |
    A          A D
  
    Every time when the process is reparented, it is added to the orphan list
    of the previous parent:
  
    A->orphan = B
    D->orphan = NULL
  
    When the A process will close the process descriptor to the B process,
    the B process will be reparented to the init process.
      B            B - init
      |   ---->
    A D          A   D
  
    A->orphan = B
    D->orphan = B
  
    In this scenario, the B process is in the orphan list of A and D.
  
    When the last process descriptor is closed instead of reparenting
    it to the reaper let it stay with the debugger process and set
    our previews parent to the reaper.
  
    Add test case for this situation.
    Notice that without this patch the kernel will crash with this test case:
    panic: orphan 0xfffff8000e990530 of 0xfffff8000e990000 has unexpected oppid 1
  
    Reviewed by:  markj, kib
    Differential Revision:        https://reviews.freebsd.org/D20361

Modified:
  stable/12/sys/kern/sys_procdesc.c
  stable/12/tests/sys/kern/ptrace_test.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/kern/sys_procdesc.c
==============================================================================
--- stable/12/sys/kern/sys_procdesc.c	Tue Sep 10 20:15:52 2019	(r352180)
+++ stable/12/sys/kern/sys_procdesc.c	Tue Sep 10 20:18:06 2019	(r352181)
@@ -416,7 +416,13 @@ procdesc_close(struct file *fp, struct thread *td)
 			 * terminate with prejudice.
 			 */
 			p->p_sigparent = SIGCHLD;
-			proc_reparent(p, p->p_reaper, true);
+			if ((p->p_flag & P_TRACED) == 0) {
+				proc_reparent(p, p->p_reaper, true);
+			} else {
+				clear_orphan(p);
+				p->p_oppid = p->p_reaper->p_pid;
+				proc_add_orphan(p, p->p_reaper);
+			}
 			if ((pd->pd_flags & PDF_DAEMON) == 0)
 				kern_psignal(p, SIGKILL);
 			PROC_UNLOCK(p);

Modified: stable/12/tests/sys/kern/ptrace_test.c
==============================================================================
--- stable/12/tests/sys/kern/ptrace_test.c	Tue Sep 10 20:15:52 2019	(r352180)
+++ stable/12/tests/sys/kern/ptrace_test.c	Tue Sep 10 20:18:06 2019	(r352181)
@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/time.h>
 #include <sys/procctl.h>
 #define	_WANT_MIPS_REGNUM
+#include <sys/procdesc.h>
 #include <sys/ptrace.h>
 #include <sys/queue.h>
 #include <sys/runq.h>
@@ -3906,6 +3907,60 @@ ATF_TC_BODY(ptrace__PT_LWPINFO_stale_siginfo, tc)
 	ATF_REQUIRE(errno == ECHILD);
 }
 
+/*
+ * Verify that when the process is traced that it isn't reparent
+ * to the init process when we close all process descriptors.
+ */
+ATF_TC(ptrace__proc_reparent);
+ATF_TC_HEAD(ptrace__proc_reparent, tc)
+{
+
+	atf_tc_set_md_var(tc, "timeout", "2");
+}
+ATF_TC_BODY(ptrace__proc_reparent, tc)
+{
+	pid_t traced, debuger, wpid;
+	int pd, status;
+
+	traced = pdfork(&pd, 0);
+	ATF_REQUIRE(traced >= 0);
+	if (traced == 0) {
+		raise(SIGSTOP);
+		exit(0);
+	}
+	ATF_REQUIRE(pd >= 0);
+
+	debuger = fork();
+	ATF_REQUIRE(debuger >= 0);
+	if (debuger == 0) {
+		/* The traced process is reparented to debuger. */
+		ATF_REQUIRE(ptrace(PT_ATTACH, traced, 0, 0) == 0);
+		wpid = waitpid(traced, &status, 0);
+		ATF_REQUIRE(wpid == traced);
+		ATF_REQUIRE(WIFSTOPPED(status));
+		ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
+		ATF_REQUIRE(close(pd) == 0);
+		ATF_REQUIRE(ptrace(PT_DETACH, traced, (caddr_t)1, 0) == 0);
+
+		/* We closed pd so we should not have any child. */
+		wpid = wait(&status);
+		ATF_REQUIRE(wpid == -1);
+		ATF_REQUIRE(errno == ECHILD);
+
+		exit(0);
+	}
+
+	ATF_REQUIRE(close(pd) == 0);
+	wpid = waitpid(debuger, &status, 0);
+	ATF_REQUIRE(wpid == debuger);
+	ATF_REQUIRE(WEXITSTATUS(status) == 0);
+
+	/* Check if we still have any child. */
+	wpid = wait(&status);
+	ATF_REQUIRE(wpid == -1);
+	ATF_REQUIRE(errno == ECHILD);
+}
+
 ATF_TP_ADD_TCS(tp)
 {
 
@@ -3967,6 +4022,7 @@ ATF_TP_ADD_TCS(tp)
 	ATF_TP_ADD_TC(tp, ptrace__PT_CONTINUE_different_thread);
 #endif
 	ATF_TP_ADD_TC(tp, ptrace__PT_LWPINFO_stale_siginfo);
+	ATF_TP_ADD_TC(tp, ptrace__proc_reparent);
 
 	return (atf_no_error());
 }