uprobes: Change uprobe_copy_process() to dup return_instances (248d3a7b) · Commits · 戴 / test

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>

kernel/events/uprobes.c

+43 −0

Original line number	Diff line number	Diff line
		@@ -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");
		}

		/*

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