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authorOleg Nesterov <oleg@redhat.com>2009-09-23 15:56:44 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-24 07:20:59 -0700
commita7f0765edfd53aed09cb7b0e15863688b39447de (patch)
treec89adfe418f9988ad4044e0f22827458bdf6b155 /kernel/ptrace.c
parent1dd3a27326d307952f8ad2499478c84dc7311517 (diff)
downloadlinux-2.6.34-ux500-a7f0765edfd53aed09cb7b0e15863688b39447de.tar.gz
ptrace: __ptrace_detach: do __wake_up_parent() if we reap the tracee
The bug is old, it wasn't cause by recent changes. Test case: static void *tfunc(void *arg) { int pid = (long)arg; assert(ptrace(PTRACE_ATTACH, pid, NULL, NULL) == 0); kill(pid, SIGKILL); sleep(1); return NULL; } int main(void) { pthread_t th; long pid = fork(); if (!pid) pause(); signal(SIGCHLD, SIG_IGN); assert(pthread_create(&th, NULL, tfunc, (void*)pid) == 0); int r = waitpid(-1, NULL, __WNOTHREAD); printf("waitpid: %d %m\n", r); return 0; } Before the patch this program hangs, after this patch waitpid() correctly fails with errno == -ECHILD. The problem is, __ptrace_detach() reaps the EXIT_ZOMBIE tracee if its ->real_parent is our sub-thread and we ignore SIGCHLD. But in this case we should wake up other threads which can sleep in do_wait(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Vitaly Mayatskikh <vmayatsk@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/ptrace.c')
-rw-r--r--kernel/ptrace.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 307c285af59..23bd09cd042 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -266,9 +266,10 @@ static int ignoring_children(struct sighand_struct *sigh)
* or self-reaping. Do notification now if it would have happened earlier.
* If it should reap itself, return true.
*
- * If it's our own child, there is no notification to do.
- * But if our normal children self-reap, then this child
- * was prevented by ptrace and we must reap it now.
+ * If it's our own child, there is no notification to do. But if our normal
+ * children self-reap, then this child was prevented by ptrace and we must
+ * reap it now, in that case we must also wake up sub-threads sleeping in
+ * do_wait().
*/
static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
{
@@ -278,8 +279,10 @@ static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
if (!task_detached(p) && thread_group_empty(p)) {
if (!same_thread_group(p->real_parent, tracer))
do_notify_parent(p, p->exit_signal);
- else if (ignoring_children(tracer->sighand))
+ else if (ignoring_children(tracer->sighand)) {
+ __wake_up_parent(p, tracer);
p->exit_signal = -1;
+ }
}
if (task_detached(p)) {
/* Mark it as in the process of being reaped. */