| Subject | Re: [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes: register/unregister probes. | From | Peter Zijlstra <> | Date | Tue, 25 Jan 2011 13:15:44 +0100 |
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On Thu, 2010-12-16 at 15:28 +0530, Srikar Dronamraju wrote: > +/* Returns 0 if it can install one probe */ > +int register_uprobe(struct inode *inode, unsigned long offset, > + struct uprobe_consumer *consumer) > +{ > + struct prio_tree_iter iter; > + struct list_head tmp_list; > + struct address_space *mapping; > + struct mm_struct *mm, *tmpmm; > + struct vm_area_struct *vma; > + struct uprobe *uprobe; > + int ret = -1; > + > + if (!inode || !consumer || consumer->next) > + return -EINVAL; > + uprobe = uprobes_add(inode, offset); > + INIT_LIST_HEAD(&tmp_list); > + > + mapping = inode->i_mapping; > + > + mutex_lock(&uprobes_mutex); > + if (uprobe->consumers) { > + ret = 0; > + goto consumers_add; > + } > + > + spin_lock(&mapping->i_mmap_lock); > + vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, 0) { > + if (!atomic_inc_not_zero(&vma->vm_mm->mm_users)) > + continue; > + > + mm = vma->vm_mm; > + if (!valid_vma(vma)) { > + mmput(mm); > + continue; > + } > + > + list_add(&mm->uprobes_list, &tmp_list); > + mm->uprobes_vaddr = vma->vm_start + offset; > + } > + spin_unlock(&mapping->i_mmap_lock);
Both this and unregister are racy, what is to say: - the vma didn't get removed from the mm - no new matching vma got added
> + if (list_empty(&tmp_list)) { > + ret = 0; > + goto consumers_add; > + } > + list_for_each_entry_safe(mm, tmpmm, &tmp_list, uprobes_list) { > + if (!install_uprobe(mm, uprobe)) > + ret = 0; > + list_del(&mm->uprobes_list); > + mmput(mm); > + } > + > +consumers_add: > + add_consumer(uprobe, consumer); > + mutex_unlock(&uprobes_mutex); > + put_uprobe(uprobe); > + return ret; > +} > +
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