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Clear P_TRACED before reparenting a detached process back to its

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original parent. Otherwise the debugee will be set as an orphan of
the debugger.

Add tests for tracing forks via PT_FOLLOW_FORK.

Reviewed by:	kib
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D2809
This commit is contained in:
John Baldwin 2015-08-01 16:27:52 +00:00
parent 458fdd97ab
commit 98685dc8af
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=286158
2 changed files with 536 additions and 56 deletions
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11
sys/kern/sys_process.c
View File

@ -947,7 +947,15 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
}
break;
case PT_DETACH:
/* reset process parent */
/*
* Reset the process parent.
*
* NB: This clears P_TRACED before reparenting
* a detached process back to its original
* parent. Otherwise the debugee will be set
* as an orphan of the debugger.
*/
p->p_flag &= ~(P_TRACED | P_WAITED | P_FOLLOWFORK);
if (p->p_oppid != p->p_pptr->p_pid) {
PROC_LOCK(p->p_pptr);
sigqueue_take(p->p_ksi);
@ -963,7 +971,6 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
} else
CTR1(KTR_PTRACE, "PT_DETACH: pid %d", p->p_pid);
p->p_oppid = 0;
p->p_flag &= ~(P_TRACED | P_WAITED | P_FOLLOWFORK);
p->p_stops = 0;
/* should we send SIGCHLD? */

581
tests/sys/kern/ptrace_test.c
View File

@ -50,7 +50,7 @@ __FBSDID("$FreeBSD$");
#exp " not met"); \
} while (0)
static void __dead2
static __dead2 void
child_fail_require(const char *file, int line, const char *str)
{
char buf[128];
@ -60,6 +60,58 @@ child_fail_require(const char *file, int line, const char *str)
_exit(32);
}
static void
trace_me(void)
{
/* Attach the parent process as a tracer of this process. */
CHILD_REQUIRE(ptrace(PT_TRACE_ME, 0, NULL, 0) != -1);
/* Trigger a stop. */
raise(SIGSTOP);
}
static void
attach_child(pid_t pid)
{
pid_t wpid;
int status;
ATF_REQUIRE(ptrace(PT_ATTACH, pid, NULL, 0) == 0);
wpid = waitpid(pid, &status, 0);
ATF_REQUIRE(wpid == pid);
ATF_REQUIRE(WIFSTOPPED(status));
ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
}
static void
wait_for_zombie(pid_t pid)
{
/*
* Wait for a process to exit. This is kind of gross, but
* there is not a better way.
*/
for (;;) {
struct kinfo_proc kp;
size_t len;
int mib[4];
mib[0] = CTL_KERN;
mib[1] = KERN_PROC;
mib[2] = KERN_PROC_PID;
mib[3] = pid;
len = sizeof(kp);
if (sysctl(mib, nitems(mib), &kp, &len, NULL, 0) == -1) {
/* The KERN_PROC_PID sysctl fails for zombies. */
ATF_REQUIRE(errno == ESRCH);
break;
}
usleep(5000);
}
}
/*
* Verify that a parent debugger process "sees" the exit of a debugged
* process exactly once when attached via PT_TRACE_ME.
@ -73,10 +125,7 @@ ATF_TC_BODY(ptrace__parent_wait_after_trace_me, tc)
ATF_REQUIRE((child = fork()) != -1);
if (child == 0) {
/* Child process. */
CHILD_REQUIRE(ptrace(PT_TRACE_ME, 0, NULL, 0) != -1);
/* Trigger a stop. */
raise(SIGSTOP);
trace_me();
exit(1);
}
@ -131,13 +180,7 @@ ATF_TC_BODY(ptrace__parent_wait_after_attach, tc)
/* Parent process. */
/* Attach to the child process. */
ATF_REQUIRE(ptrace(PT_ATTACH, child, NULL, 0) == 0);
/* The first wait() should report the SIGSTOP from PT_ATTACH. */
wpid = waitpid(child, &status, 0);
ATF_REQUIRE(wpid == child);
ATF_REQUIRE(WIFSTOPPED(status));
ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
attach_child(child);
/* Continue the child ignoring the SIGSTOP. */
ATF_REQUIRE(ptrace(PT_CONTINUE, child, (caddr_t)1, 0) != -1);
@ -223,27 +266,7 @@ ATF_TC_BODY(ptrace__parent_sees_exit_after_child_debugger, tc)
ATF_REQUIRE(read(cpipe[0], &c, sizeof(c)) == 0);
close(cpipe[0]);
/*
* Wait for the child to exit. This is kind of gross, but
* there is not a better way.
*/
for (;;) {
struct kinfo_proc kp;
size_t len;
int mib[4];
mib[0] = CTL_KERN;
mib[1] = KERN_PROC;
mib[2] = KERN_PROC_PID;
mib[3] = child;
len = sizeof(kp);
if (sysctl(mib, nitems(mib), &kp, &len, NULL, 0) == -1) {
/* The KERN_PROC_PID sysctl fails for zombies. */
ATF_REQUIRE(errno == ESRCH);
break;
}
usleep(5000);
}
wait_for_zombie(child);
/*
* This wait should return a pid of 0 to indicate no status to
@ -357,27 +380,7 @@ ATF_TC_BODY(ptrace__parent_sees_exit_after_unrelated_debugger, tc)
ATF_REQUIRE(read(cpipe[0], &c, sizeof(c)) == 0);
close(cpipe[0]);
/*
* Wait for the child to exit. This is kind of gross, but
* there is not a better way.
*/
for (;;) {
struct kinfo_proc kp;
size_t len;
int mib[4];
mib[0] = CTL_KERN;
mib[1] = KERN_PROC;
mib[2] = KERN_PROC_PID;
mib[3] = child;
len = sizeof(kp);
if (sysctl(mib, nitems(mib), &kp, &len, NULL, 0) == -1) {
/* The KERN_PROC_PID sysctl fails for zombies. */
ATF_REQUIRE(errno == ESRCH);
break;
}
usleep(5000);
}
wait_for_zombie(child);
/*
* This wait should return a pid of 0 to indicate no status to
@ -401,6 +404,468 @@ ATF_TC_BODY(ptrace__parent_sees_exit_after_unrelated_debugger, tc)
ATF_REQUIRE(WEXITSTATUS(status) == 1);
}
/*
* The parent process should always act the same regardless of how the
* debugger is attached to it.
*/
static __dead2 void
follow_fork_parent(void)
{
pid_t fpid, wpid;
int status;
CHILD_REQUIRE((fpid = fork()) != -1);
if (fpid == 0)
/* Child */
exit(2);
wpid = waitpid(fpid, &status, 0);
CHILD_REQUIRE(wpid == fpid);
CHILD_REQUIRE(WIFEXITED(status));
CHILD_REQUIRE(WEXITSTATUS(status) == 2);
exit(1);
}
/*
* Helper routine for follow fork tests. This waits for two stops
* that report both "sides" of a fork. It returns the pid of the new
* child process.
*/
static pid_t
handle_fork_events(pid_t parent)
{
struct ptrace_lwpinfo pl;
bool fork_reported[2];
pid_t child, wpid;
int i, status;
fork_reported[0] = false;
fork_reported[1] = false;
child = -1;
/*
* Each process should report a fork event. The parent should
* report a PL_FLAG_FORKED event, and the child should report
* a PL_FLAG_CHILD event.
*/
for (i = 0; i < 2; i++) {
wpid = wait(&status);
ATF_REQUIRE(wpid > 0);
ATF_REQUIRE(WIFSTOPPED(status));
ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl,
sizeof(pl)) != -1);
ATF_REQUIRE((pl.pl_flags & (PL_FLAG_FORKED | PL_FLAG_CHILD)) !=
0);
ATF_REQUIRE((pl.pl_flags & (PL_FLAG_FORKED | PL_FLAG_CHILD)) !=
(PL_FLAG_FORKED | PL_FLAG_CHILD));
if (pl.pl_flags & PL_FLAG_CHILD) {
ATF_REQUIRE(wpid != parent);
ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
ATF_REQUIRE(!fork_reported[1]);
if (child == -1)
child = wpid;
else
ATF_REQUIRE(child == wpid);
fork_reported[1] = true;
} else {
ATF_REQUIRE(wpid == parent);
ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
ATF_REQUIRE(!fork_reported[0]);
if (child == -1)
child = pl.pl_child_pid;
else
ATF_REQUIRE(child == pl.pl_child_pid);
fork_reported[0] = true;
}
}
return (child);
}
/*
* Verify that a new child process is stopped after a followed fork and
* that the traced parent sees the exit of the child after the debugger
* when both processes remain attached to the debugger.
*/
ATF_TC_WITHOUT_HEAD(ptrace__follow_fork_both_attached);
ATF_TC_BODY(ptrace__follow_fork_both_attached, tc)
{
pid_t children[0], fpid, wpid;
int status;
ATF_REQUIRE((fpid = fork()) != -1);
if (fpid == 0) {
trace_me();
follow_fork_parent();
}
/* Parent process. */
children[0] = fpid;
/* The first wait() should report the stop from SIGSTOP. */
wpid = waitpid(children[0], &status, 0);
ATF_REQUIRE(wpid == children[0]);
ATF_REQUIRE(WIFSTOPPED(status));
ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
ATF_REQUIRE(ptrace(PT_FOLLOW_FORK, children[0], NULL, 1) != -1);
/* Continue the child ignoring the SIGSTOP. */
ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
children[1] = handle_fork_events(children[0]);
ATF_REQUIRE(children[1] > 0);
ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
ATF_REQUIRE(ptrace(PT_CONTINUE, children[1], (caddr_t)1, 0) != -1);
/*
* The child can't exit until the grandchild reports status, so the
* grandchild should report its exit first to the debugger.
*/
wpid = wait(&status);
ATF_REQUIRE(wpid == children[1]);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 2);
wpid = wait(&status);
ATF_REQUIRE(wpid == children[0]);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 1);
wpid = wait(&status);
ATF_REQUIRE(wpid == -1);
ATF_REQUIRE(errno == ECHILD);
}
/*
* Verify that a new child process is stopped after a followed fork
* and that the traced parent sees the exit of the child when the new
* child process is detached after it reports its fork.
*/
ATF_TC_WITHOUT_HEAD(ptrace__follow_fork_child_detached);
ATF_TC_BODY(ptrace__follow_fork_child_detached, tc)
{
pid_t children[0], fpid, wpid;
int status;
ATF_REQUIRE((fpid = fork()) != -1);
if (fpid == 0) {
trace_me();
follow_fork_parent();
}
/* Parent process. */
children[0] = fpid;
/* The first wait() should report the stop from SIGSTOP. */
wpid = waitpid(children[0], &status, 0);
ATF_REQUIRE(wpid == children[0]);
ATF_REQUIRE(WIFSTOPPED(status));
ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
ATF_REQUIRE(ptrace(PT_FOLLOW_FORK, children[0], NULL, 1) != -1);
/* Continue the child ignoring the SIGSTOP. */
ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
children[1] = handle_fork_events(children[0]);
ATF_REQUIRE(children[1] > 0);
ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
ATF_REQUIRE(ptrace(PT_DETACH, children[1], (caddr_t)1, 0) != -1);
/*
* Should not see any status from the grandchild now, only the
* child.
*/
wpid = wait(&status);
ATF_REQUIRE(wpid == children[0]);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 1);
wpid = wait(&status);
ATF_REQUIRE(wpid == -1);
ATF_REQUIRE(errno == ECHILD);
}
/*
* Verify that a new child process is stopped after a followed fork
* and that the traced parent sees the exit of the child when the
* traced parent is detached after the fork.
*/
ATF_TC_WITHOUT_HEAD(ptrace__follow_fork_parent_detached);
ATF_TC_BODY(ptrace__follow_fork_parent_detached, tc)
{
pid_t children[0], fpid, wpid;
int status;
ATF_REQUIRE((fpid = fork()) != -1);
if (fpid == 0) {
trace_me();
follow_fork_parent();
}
/* Parent process. */
children[0] = fpid;
/* The first wait() should report the stop from SIGSTOP. */
wpid = waitpid(children[0], &status, 0);
ATF_REQUIRE(wpid == children[0]);
ATF_REQUIRE(WIFSTOPPED(status));
ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
ATF_REQUIRE(ptrace(PT_FOLLOW_FORK, children[0], NULL, 1) != -1);
/* Continue the child ignoring the SIGSTOP. */
ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
children[1] = handle_fork_events(children[0]);
ATF_REQUIRE(children[1] > 0);
ATF_REQUIRE(ptrace(PT_DETACH, children[0], (caddr_t)1, 0) != -1);
ATF_REQUIRE(ptrace(PT_CONTINUE, children[1], (caddr_t)1, 0) != -1);
/*
* The child can't exit until the grandchild reports status, so the
* grandchild should report its exit first to the debugger.
*
* Even though the child process is detached, it is still a
* child of the debugger, so it will still report it's exit
* after the grandchild.
*/
wpid = wait(&status);
ATF_REQUIRE(wpid == children[1]);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 2);
wpid = wait(&status);
ATF_REQUIRE(wpid == children[0]);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 1);
wpid = wait(&status);
ATF_REQUIRE(wpid == -1);
ATF_REQUIRE(errno == ECHILD);
}
static void
attach_fork_parent(int cpipe[2])
{
pid_t fpid;
close(cpipe[0]);
/* Double-fork to disassociate from the debugger. */
CHILD_REQUIRE((fpid = fork()) != -1);
if (fpid != 0)
exit(3);
/* Send the pid of the disassociated child to the debugger. */
fpid = getpid();
CHILD_REQUIRE(write(cpipe[1], &fpid, sizeof(fpid)) == sizeof(fpid));
/* Wait for the debugger to attach. */
CHILD_REQUIRE(read(cpipe[1], &fpid, sizeof(fpid)) == 0);
}
/*
* Verify that a new child process is stopped after a followed fork and
* that the traced parent sees the exit of the child after the debugger
* when both processes remain attached to the debugger. In this test
* the parent that forks is not a direct child of the debugger.
*/
ATF_TC_WITHOUT_HEAD(ptrace__follow_fork_both_attached_unrelated_debugger);
ATF_TC_BODY(ptrace__follow_fork_both_attached_unrelated_debugger, tc)
{
pid_t children[0], fpid, wpid;
int cpipe[2], status;
ATF_REQUIRE(pipe(cpipe) == 0);
ATF_REQUIRE((fpid = fork()) != -1);
if (fpid == 0) {
attach_fork_parent(cpipe);
follow_fork_parent();
}
/* Parent process. */
close(cpipe[1]);
/* Wait for the direct child to exit. */
wpid = waitpid(fpid, &status, 0);
ATF_REQUIRE(wpid == fpid);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 3);
/* Read the pid of the fork parent. */
ATF_REQUIRE(read(cpipe[0], &children[0], sizeof(children[0])) ==
sizeof(children[0]));
/* Attach to the fork parent. */
attach_child(children[0]);
ATF_REQUIRE(ptrace(PT_FOLLOW_FORK, children[0], NULL, 1) != -1);
/* Continue the fork parent ignoring the SIGSTOP. */
ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
/* Signal the fork parent to continue. */
close(cpipe[0]);
children[1] = handle_fork_events(children[0]);
ATF_REQUIRE(children[1] > 0);
ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
ATF_REQUIRE(ptrace(PT_CONTINUE, children[1], (caddr_t)1, 0) != -1);
/*
* The fork parent can't exit until the child reports status,
* so the child should report its exit first to the debugger.
*/
wpid = wait(&status);
ATF_REQUIRE(wpid == children[1]);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 2);
wpid = wait(&status);
ATF_REQUIRE(wpid == children[0]);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 1);
wpid = wait(&status);
ATF_REQUIRE(wpid == -1);
ATF_REQUIRE(errno == ECHILD);
}
/*
* Verify that a new child process is stopped after a followed fork
* and that the traced parent sees the exit of the child when the new
* child process is detached after it reports its fork. In this test
* the parent that forks is not a direct child of the debugger.
*/
ATF_TC_WITHOUT_HEAD(ptrace__follow_fork_child_detached_unrelated_debugger);
ATF_TC_BODY(ptrace__follow_fork_child_detached_unrelated_debugger, tc)
{
pid_t children[0], fpid, wpid;
int cpipe[2], status;
ATF_REQUIRE(pipe(cpipe) == 0);
ATF_REQUIRE((fpid = fork()) != -1);
if (fpid == 0) {
attach_fork_parent(cpipe);
follow_fork_parent();
}
/* Parent process. */
close(cpipe[1]);
/* Wait for the direct child to exit. */
wpid = waitpid(fpid, &status, 0);
ATF_REQUIRE(wpid == fpid);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 3);
/* Read the pid of the fork parent. */
ATF_REQUIRE(read(cpipe[0], &children[0], sizeof(children[0])) ==
sizeof(children[0]));
/* Attach to the fork parent. */
attach_child(children[0]);
ATF_REQUIRE(ptrace(PT_FOLLOW_FORK, children[0], NULL, 1) != -1);
/* Continue the fork parent ignoring the SIGSTOP. */
ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
/* Signal the fork parent to continue. */
close(cpipe[0]);
children[1] = handle_fork_events(children[0]);
ATF_REQUIRE(children[1] > 0);
ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
ATF_REQUIRE(ptrace(PT_DETACH, children[1], (caddr_t)1, 0) != -1);
/*
* Should not see any status from the child now, only the fork
* parent.
*/
wpid = wait(&status);
ATF_REQUIRE(wpid == children[0]);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 1);
wpid = wait(&status);
ATF_REQUIRE(wpid == -1);
ATF_REQUIRE(errno == ECHILD);
}
/*
* Verify that a new child process is stopped after a followed fork
* and that the traced parent sees the exit of the child when the
* traced parent is detached after the fork. In this test the parent
* that forks is not a direct child of the debugger.
*/
ATF_TC_WITHOUT_HEAD(ptrace__follow_fork_parent_detached_unrelated_debugger);
ATF_TC_BODY(ptrace__follow_fork_parent_detached_unrelated_debugger, tc)
{
pid_t children[0], fpid, wpid;
int cpipe[2], status;
ATF_REQUIRE(pipe(cpipe) == 0);
ATF_REQUIRE((fpid = fork()) != -1);
if (fpid == 0) {
attach_fork_parent(cpipe);
follow_fork_parent();
}
/* Parent process. */
close(cpipe[1]);
/* Wait for the direct child to exit. */
wpid = waitpid(fpid, &status, 0);
ATF_REQUIRE(wpid == fpid);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 3);
/* Read the pid of the fork parent. */
ATF_REQUIRE(read(cpipe[0], &children[0], sizeof(children[0])) ==
sizeof(children[0]));
/* Attach to the fork parent. */
attach_child(children[0]);
ATF_REQUIRE(ptrace(PT_FOLLOW_FORK, children[0], NULL, 1) != -1);
/* Continue the fork parent ignoring the SIGSTOP. */
ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
/* Signal the fork parent to continue. */
close(cpipe[0]);
children[1] = handle_fork_events(children[0]);
ATF_REQUIRE(children[1] > 0);
ATF_REQUIRE(ptrace(PT_DETACH, children[0], (caddr_t)1, 0) != -1);
ATF_REQUIRE(ptrace(PT_CONTINUE, children[1], (caddr_t)1, 0) != -1);
/*
* Should not see any status from the fork parent now, only
* the child.
*/
wpid = wait(&status);
ATF_REQUIRE(wpid == children[1]);
ATF_REQUIRE(WIFEXITED(status));
ATF_REQUIRE(WEXITSTATUS(status) == 2);
wpid = wait(&status);
ATF_REQUIRE(wpid == -1);
ATF_REQUIRE(errno == ECHILD);
}
ATF_TP_ADD_TCS(tp)
{
@ -408,6 +873,14 @@ ATF_TP_ADD_TCS(tp)
ATF_TP_ADD_TC(tp, ptrace__parent_wait_after_attach);
ATF_TP_ADD_TC(tp, ptrace__parent_sees_exit_after_child_debugger);
ATF_TP_ADD_TC(tp, ptrace__parent_sees_exit_after_unrelated_debugger);
ATF_TP_ADD_TC(tp, ptrace__follow_fork_both_attached);
ATF_TP_ADD_TC(tp, ptrace__follow_fork_child_detached);
ATF_TP_ADD_TC(tp, ptrace__follow_fork_parent_detached);
ATF_TP_ADD_TC(tp, ptrace__follow_fork_both_attached_unrelated_debugger);
ATF_TP_ADD_TC(tp,
ptrace__follow_fork_child_detached_unrelated_debugger);
ATF_TP_ADD_TC(tp,
ptrace__follow_fork_parent_detached_unrelated_debugger);
return (atf_no_error());
}