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>
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@ -1366,12 +1366,55 @@ static struct uprobe_task *get_utask(void)
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return current->utask;
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}
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static int dup_utask(struct task_struct *t, struct uprobe_task *o_utask)
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{
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struct uprobe_task *n_utask;
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struct return_instance **p, *o, *n;
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n_utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
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if (!n_utask)
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return -ENOMEM;
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t->utask = n_utask;
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p = &n_utask->return_instances;
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for (o = o_utask->return_instances; o; o = o->next) {
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n = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
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if (!n)
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return -ENOMEM;
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*n = *o;
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atomic_inc(&n->uprobe->ref);
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n->next = NULL;
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*p = n;
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p = &n->next;
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n_utask->depth++;
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}
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return 0;
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}
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static void uprobe_warn(struct task_struct *t, const char *msg)
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{
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pr_warn("uprobe: %s:%d failed to %s\n",
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current->comm, current->pid, msg);
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}
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/*
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* Called in context of a new clone/fork from copy_process.
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*/
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void uprobe_copy_process(struct task_struct *t)
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{
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struct uprobe_task *utask = current->utask;
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struct mm_struct *mm = current->mm;
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t->utask = NULL;
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if (mm == t->mm || !utask || !utask->return_instances)
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return;
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if (dup_utask(t, utask))
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return uprobe_warn(t, "dup ret instances");
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}
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/*
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