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kill PT_ATTACHED 

Since the patch

	"Fix ptrace_attach()/ptrace_traceme()/de_thread() race"
	commit f5b40e363a

we set PT_ATTACHED and change child->parent "atomically" wrt task_list lock.

This means we can remove the checks like "PT_ATTACHED && ->parent != ptracer"
which were needed to catch the "ptrace attach is in progress" case.  We can
also remove the flag itself since nobody else uses it.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2008-02-08 04:18:58 -08:00 committed by Linus Torvalds
parent 01b8b07a5d
commit 6b39c7bfbd
4 changed files with 3 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/ptrace.h
View File

@ -67,7 +67,6 @@
#define PT_TRACE_EXEC 0x00000080 #define PT_TRACE_EXEC 0x00000080
#define PT_TRACE_VFORK_DONE 0x00000100 #define PT_TRACE_VFORK_DONE 0x00000100
#define PT_TRACE_EXIT 0x00000200 #define PT_TRACE_EXIT 0x00000200
#define PT_ATTACHED 0x00000400 /* parent != real_parent */
#define PT_TRACE_MASK 0x000003f4 #define PT_TRACE_MASK 0x000003f4

13
kernel/exit.c
View File

@ -1514,18 +1514,7 @@ static int wait_task_continued(struct task_struct *p, int noreap,
static inline int my_ptrace_child(struct task_struct *p) static inline int my_ptrace_child(struct task_struct *p)
{ {
if (!(p->ptrace & PT_PTRACED)) return p->ptrace & PT_PTRACED;
return 0;
if (!(p->ptrace & PT_ATTACHED))
return 1;
/*
* This child was PTRACE_ATTACH'd. We should be seeing it only if
* we are the attacher. If we are the real parent, this is a race
* inside ptrace_attach. It is waiting for the tasklist_lock,
* which we have to switch the parent links, but has already set
* the flags in p->ptrace.
*/
return (p->parent != p->real_parent);
} }
static long do_wait(pid_t pid, int options, struct siginfo __user *infop, static long do_wait(pid_t pid, int options, struct siginfo __user *infop,

6
kernel/ptrace.c
View File

@ -100,8 +100,7 @@ int ptrace_check_attach(struct task_struct *child, int kill)
*/ */
read_lock(&tasklist_lock); read_lock(&tasklist_lock);
if ((child->ptrace & PT_PTRACED) && child->parent == current && if ((child->ptrace & PT_PTRACED) && child->parent == current &&
(!(child->ptrace & PT_ATTACHED) || child->real_parent != current) child->signal != NULL) {
&& child->signal != NULL) {
ret = 0; ret = 0;
spin_lock_irq(&child->sighand->siglock); spin_lock_irq(&child->sighand->siglock);
if (task_is_stopped(child)) if (task_is_stopped(child))
@ -200,8 +199,7 @@ repeat:
goto bad; goto bad;
/* Go */ /* Go */
task->ptrace |= PT_PTRACED | ((task->real_parent != current) task->ptrace |= PT_PTRACED;
? PT_ATTACHED : 0);
if (capable(CAP_SYS_PTRACE)) if (capable(CAP_SYS_PTRACE))
task->ptrace |= PT_PTRACE_CAP; task->ptrace |= PT_PTRACE_CAP;

5
kernel/signal.c
View File

@ -1556,11 +1556,6 @@ static inline int may_ptrace_stop(void)
{ {
if (!likely(current->ptrace & PT_PTRACED)) if (!likely(current->ptrace & PT_PTRACED))
return 0; return 0;
if (unlikely(current->parent == current->real_parent &&
(current->ptrace & PT_ATTACHED)))
return 0;
/* /*
* Are we in the middle of do_coredump? * Are we in the middle of do_coredump?
* If so and our tracer is also part of the coredump stopping * If so and our tracer is also part of the coredump stopping