path: root/kernel
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authorOleg Nesterov <>2009-04-02 16:58:21 -0700
committerLinus Torvalds <>2009-04-02 19:05:00 -0700
commit95a3540da9c81a5987be810e1d9a83640a366bd5 (patch)
treed5143f232f885f6aa8829288dc0ceb2cd9e6e34e /kernel
parentbb24c679a51b1a9b726b901330649e3861814ac0 (diff)
ptrace_detach: the wrong wakeup breaks the ERESTARTxxx logic
Another ancient bug. Consider this trivial test-case, int main(void) { int pid = fork(); if (pid) { ptrace(PTRACE_ATTACH, pid, NULL, NULL); wait(NULL); ptrace(PTRACE_DETACH, pid, NULL, NULL); } else { pause(); printf("WE HAVE A KERNEL BUG!!!\n"); } return 0; } the child must not "escape" for sys_pause(), but it can and this was seen in practice. This is because ptrace_detach does: if (!child->exit_state) wake_up_process(child); this wakeup can happen after this child has already restarted sys_pause(), because it gets another wakeup from ptrace_untrace(). With or without this patch, perhaps sys_pause() needs a fix. But this wakeup also breaks the SIGNAL_STOP_STOPPED logic in ptrace_untrace(). Remove this wakeup. The caller saw this task in TASK_TRACED state, and unless it was SIGKILL'ed in between __ptrace_unlink()->ptrace_untrace() should handle this case correctly. If it was SIGKILL'ed, we don't need to wakup the dying tracee too. Signed-off-by: Oleg Nesterov <> Cc: Jerome Marchand <> Acked-by: Roland McGrath <> Cc: Denys Vlasenko <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'kernel')
1 files changed, 0 insertions, 4 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index f5a9fa5aafa1..296e8105863a 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -301,11 +301,7 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
if (child->ptrace) {
child->exit_code = data;
dead = __ptrace_detach(current, child);
- if (!child->exit_state)
- wake_up_process(child);