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Subject[PATCH 1/5] uprobes: Change the callsite of uprobe_copy_process()
Preparation for the next patches.

Move the callsite of uprobe_copy_process() in copy_process() down
to the succesfull return. We do not care if copy_process() fails,
uprobe_free_utask() won't be called in this case so the wrong
->utask != NULL doesn't matter.

OTOH, with this change we know that copy_process() can't fail when
uprobe_copy_process() is called, the new task should either return
to user-mode or call do_exit(). This way uprobe_copy_process() can:

1. setup p->utask != NULL if necessary

2. setup uprobes_state.xol_area

3. use task_work_add(p)

Also, move the definition of uprobe_copy_process() down so that it
can see get_utask().

Cc: stable@vger.kernel.org # 3.9+
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/events/uprobes.c | 16 ++++++++--------
kernel/fork.c | 2 +-
2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index ad8e1bd..db7a1dc 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1345,14 +1345,6 @@ void uprobe_free_utask(struct task_struct *t)
}

/*
- * Called in context of a new clone/fork from copy_process.
- */
-void uprobe_copy_process(struct task_struct *t)
-{
- t->utask = NULL;
-}
-
-/*
* Allocate a uprobe_task object for the task if if necessary.
* Called when the thread hits a breakpoint.
*
@@ -1368,6 +1360,14 @@ static struct uprobe_task *get_utask(void)
}

/*
+ * Called in context of a new clone/fork from copy_process.
+ */
+void uprobe_copy_process(struct task_struct *t)
+{
+ t->utask = NULL;
+}
+
+/*
* Current area->vaddr notion assume the trampoline address is always
* equal area->vaddr.
*
diff --git a/kernel/fork.c b/kernel/fork.c
index 086fe73..d3603b8 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1373,7 +1373,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
INIT_LIST_HEAD(&p->pi_state_list);
p->pi_state_cache = NULL;
#endif
- uprobe_copy_process(p);
/*
* sigaltstack should be cleared when sharing the same VM
*/
@@ -1490,6 +1489,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
perf_event_fork(p);

trace_task_newtask(p, clone_flags);
+ uprobe_copy_process(p);

return p;

--
1.5.5.1


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