Messages in this thread |  | | From | Namhyung Kim <> | Subject | Re: [PATCH 12/13] tracing/uprobes: Add more fetch functions | Date | Tue, 05 Nov 2013 11:17:17 +0900 |
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On Mon, 4 Nov 2013 17:44:31 +0100, Oleg Nesterov wrote: > On 11/04, Namhyung Kim wrote: >> >> 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. > > Whatever we do this address can be unmapped. For example, just because of > @invalid_address passed to trace_uprobe.c. > > We do not really care, copy_from_user() should fail. But we should not > WARN() in this case.
Okay, I see. Will remove it in the next spin.
Thanks, Namhyung
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