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authorOleg Nesterov <oleg@redhat.com>2009-04-02 16:58:14 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2009-06-15 09:40:20 -0700
commit8842593368490116911712ea5aaf6ea9dd2db7bb (patch)
tree2487291ebcdd5b3c98a0d37522440e3268c5718b
parent64cd4669da13c829635f0b668a6bd546ee472e01 (diff)
ptrace: fix possible zombie leak on PTRACE_DETACH
commit 4576145c1ecdaaea9ef8976a48335206aa1ebf91 upstream. When ptrace_detach() takes tasklist, the tracee can be SIGKILL'ed. If it has already passed exit_notify() we can leak a zombie, because a) ptracing disables the auto-reaping logic, and b) ->real_parent was not notified about the child's death. ptrace_detach() should follow the ptrace_exit's logic, change the code accordingly. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Roland McGrath <roland@redhat.com> Tested-by: Denys Vlasenko <dvlasenk@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--include/linux/ptrace.h1
-rw-r--r--kernel/ptrace.c9
2 files changed, 8 insertions, 2 deletions
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 98b93ca4db06..1a2b0cb55535 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -94,6 +94,7 @@ extern void ptrace_notify(int exit_code);
extern void __ptrace_link(struct task_struct *child,
struct task_struct *new_parent);
extern void __ptrace_unlink(struct task_struct *child);
+extern int __ptrace_detach(struct task_struct *tracer, struct task_struct *p);
extern void ptrace_fork(struct task_struct *task, unsigned long clone_flags);
#define PTRACE_MODE_READ 1
#define PTRACE_MODE_ATTACH 2
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 2f5ec7a571a8..893c2c7615d5 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -237,6 +237,8 @@ out:
int ptrace_detach(struct task_struct *child, unsigned int data)
{
+ int dead = 0;
+
if (!valid_signal(data))
return -EIO;
@@ -244,18 +246,21 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
ptrace_disable(child);
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
- /* protect against de_thread()->release_task() */
write_lock_irq(&tasklist_lock);
+ /* protect against de_thread()->release_task() */
if (child->ptrace) {
child->exit_code = data;
- __ptrace_unlink(child);
+ dead = __ptrace_detach(current, child);
if (!child->exit_state)
wake_up_process(child);
}
write_unlock_irq(&tasklist_lock);
+ if (unlikely(dead))
+ release_task(child);
+
return 0;
}