lkml.org 
[lkml]   [2013]   [Nov]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 12/13] tracing/uprobes: Add more fetch functions
Date
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


\
 
 \ /
  Last update: 2013-11-05 03:41    [W:0.197 / U:0.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site