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ptrace: skip all sigstop (v2)

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A task can be stopped and has a queued SIGSTOP, in this case we need
to resume the task twice to skip "both" signals.

v2: detect SIGSTOP in shared and per-process queues
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Andrew Vagin 2015-11-25 19:50:10 +03:00 committed by Pavel Emelyanov
parent fde1116fee
commit fa79ffd6ed
1 changed files with 49 additions and 35 deletions
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84
ptrace.c
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@ -102,6 +102,45 @@ int seize_catch_task(pid_t pid)
return ret;
}
static int skip_sigstop(int pid, int nr_signals)
{
int i, status, ret;
/*
* 1) SIGSTOP is queued, but isn't handled yet:
* SGISTOP can't be blocked, so we need to wait when the kernel
* handles this signal.
*
* Otherwise the process will be stopped immediatly after
* starting it.
*
* 2) A seized task was stopped:
* PTRACE_SEIZE doesn't affect signal or group stop state.
* Currently ptrace reported that task is in stopped state.
* We need to start task again, and it will be trapped
* immediately, because we sent PTRACE_INTERRUPT to it.
*/
for (i = 0; i < nr_signals; i++) {
ret = ptrace(PTRACE_CONT, pid, 0, 0);
if (ret) {
pr_perror("Unable to start process");
return -1;
}
ret = wait4(pid, &status, __WALL, NULL);
if (ret < 0) {
pr_perror("SEIZE %d: can't wait task", pid);
return -1;
}
if (!WIFSTOPPED(status)) {
pr_err("SEIZE %d: task not stopped after seize\n", pid);
return -1;
}
}
return 0;
}
/*
* This routine seizes task putting it into a special
* state where we can manipulate the task via ptrace
@ -112,7 +151,7 @@ int seize_catch_task(pid_t pid)
int seize_wait_task(pid_t pid, pid_t ppid, struct proc_status_creds **creds)
{
siginfo_t si;
int status;
int status, nr_sigstop;
int ret = 0, ret2, wait_errno = 0;
struct proc_status_creds cr;
@ -204,42 +243,17 @@ try_again:
if (cr.seccomp_mode != SECCOMP_MODE_DISABLED && suspend_seccomp(pid) < 0)
goto err;
if ((cr.sigpnd | cr.shdpnd) & (1 << (SIGSTOP - 1)) || si.si_signo == SIGSTOP) {
/*
* 1) SIGSTOP is queued, but isn't handled yet:
* SGISTOP can't be blocked, so we need to wait when the kernel
* handles this signal.
*
* Otherwise the process will be stopped immediatly after
* starting it.
*
* 2) A seized task was stopped:
* PTRACE_SEIZE doesn't affect signal or group stop state.
* Currently ptrace reported that task is in stopped state.
* We need to start task again, and it will be trapped
* immediately, because we sent PTRACE_INTERRUPT to it.
*/
ret = ptrace(PTRACE_CONT, pid, 0, 0);
if (ret) {
pr_perror("Unable to start process");
goto err_stop;
}
nr_sigstop = 0;
if (cr.sigpnd & (1 << (SIGSTOP - 1)))
nr_sigstop++;
if (cr.shdpnd & (1 << (SIGSTOP - 1)))
nr_sigstop++;
if (si.si_signo == SIGSTOP)
nr_sigstop++;
ret = wait4(pid, &status, __WALL, NULL);
if (ret < 0) {
pr_perror("SEIZE %d: can't wait task", pid);
if (nr_sigstop) {
if (skip_sigstop(pid, nr_sigstop))
goto err_stop;
}
if (ret != pid) {
pr_err("SEIZE %d: wrong task attached (%d)\n", pid, ret);
goto err_stop;
}
if (!WIFSTOPPED(status)) {
pr_err("SEIZE %d: task not stopped after seize\n", pid);
goto err_stop;
}
return TASK_STOPPED;
}