On Wed 19-08-20 19:46:50, Sumit Semwal wrote:
[...]
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 5066b0251ed8..136fd3c3ad7b 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -97,6 +97,21 @@ unsigned long task_statm(struct mm_struct *mm,
> return mm->total_vm;
> }
>
> +static void seq_print_vma_name(struct seq_file *m, struct vm_area_struct *vma)
> +{
> + struct mm_struct *mm = vma->vm_mm;
> + char anon_name[NAME_MAX + 1];
> + int n;
> +
> + n = access_remote_vm(mm, (unsigned long)vma_anon_name(vma),
> + anon_name, NAME_MAX, 0);
> + if (n > 0) {
> + seq_puts(m, "[anon:");
> + seq_write(m, anon_name, strnlen(anon_name, n));
> + seq_putc(m, ']');
> + }
> +}
> +
> #ifdef CONFIG_NUMA
> /*
> * Save get_task_policy() for show_numa_map().
> @@ -319,8 +334,15 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
> goto done;
> }
>
> - if (is_stack(vma))
> + if (is_stack(vma)) {
> name = "[stack]";
> + goto done;
> + }
> +
> + if (vma_anon_name(vma)) {
> + seq_pad(m, ' ');
> + seq_print_vma_name(m, vma);
> + }
> }
How can be this safe? access_remote_vm requires mmap_sem (non exlusive).
The same is the case for show_map_vma. So what would happen if a task
sets its own name? IIRC semaphore code doesn't allow read lock nesting
because any exclusive lock request in the mean time would block further
readers. Or is this allowed?
--
Michal Hocko
SUSE Labs
