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uprobes: Change uprobe_copy_process() to dup return_instances 

uprobe_copy_process() assumes that the new child doesn't need
->utask, it should be allocated by demand.

But this is not true if the forking task has the pending ret-
probes, the child should report them as well and thus it needs
the copy of parent's ->return_instances chain. Otherwise the
child crashes when it returns from the probed function.

Alternatively we could cleanup the child's stack, but this needs
per-arch changes and this is not what we want. At least systemtap
expects a .return in the child too.

Note: this change alone doesn't fix the problem, see the next
change.

Reported-by: Martin Cermak <mcermak@redhat.com>
Reported-by: David Smith <dsmith@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2013-10-13 21:18:41 +02:00
parent af0d95af79
commit 248d3a7b2f
1 changed files with 43 additions and 0 deletions
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43
kernel/events/uprobes.c
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@ -1366,12 +1366,55 @@ static struct uprobe_task *get_utask(void)
return current->utask;
}
static int dup_utask(struct task_struct *t, struct uprobe_task *o_utask)
{
struct uprobe_task *n_utask;
struct return_instance **p, *o, *n;
n_utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
if (!n_utask)
return -ENOMEM;
t->utask = n_utask;
p = &n_utask->return_instances;
for (o = o_utask->return_instances; o; o = o->next) {
n = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
if (!n)
return -ENOMEM;
*n = *o;
atomic_inc(&n->uprobe->ref);
n->next = NULL;
*p = n;
p = &n->next;
n_utask->depth++;
}
return 0;
}
static void uprobe_warn(struct task_struct *t, const char *msg)
{
pr_warn("uprobe: %s:%d failed to %s\n",
current->comm, current->pid, msg);
}
/*
* Called in context of a new clone/fork from copy_process.
*/
void uprobe_copy_process(struct task_struct *t)
{
struct uprobe_task *utask = current->utask;
struct mm_struct *mm = current->mm;
t->utask = NULL;
if (mm == t->mm || !utask || !utask->return_instances)
return;
if (dup_utask(t, utask))
return uprobe_warn(t, "dup ret instances");
}
/*