Messages in this thread |  | | From | Namhyung Kim <> | Subject | Re: [PATCH 12/13] tracing/uprobes: Add more fetch functions | Date | Mon, 04 Nov 2013 17:50:53 +0900 |
| |
On Thu, 31 Oct 2013 19:22:18 +0100, Oleg Nesterov wrote: > On 10/29, Namhyung Kim wrote: >> >> +static void __user *get_user_vaddr(unsigned long addr, struct trace_uprobe *tu) >> +{ >> + unsigned long pgoff = addr >> PAGE_SHIFT; >> + struct vm_area_struct *vma; >> + struct address_space *mapping; >> + unsigned long vaddr = 0; >> + >> + if (tu == NULL) { >> + /* A NULL tu means that we already got the vaddr */ >> + return (void __force __user *) addr; >> + } >> + >> + mapping = tu->inode->i_mapping; >> + >> + mutex_lock(&mapping->i_mmap_mutex); >> + vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { >> + if (vma->vm_mm != current->mm) >> + continue; >> + if (!(vma->vm_flags & VM_READ)) >> + continue; >> + >> + vaddr = offset_to_vaddr(vma, addr); >> + break; >> + } >> + mutex_unlock(&mapping->i_mmap_mutex); >> + >> + WARN_ON_ONCE(vaddr == 0); > > Hmm. But unless I missed something this "addr" passed as an argument can > be wrong? And if nothing else this or another thread can unmap the vma?
You mean WARN_ON_ONCE here is superfluous? I admit that it should protect concurrent vma [un]mappings. Please see my reply in other thread for a new approach.
Thanks, Namhyung
|  |