On Tue, Aug 05, 2014 at 09:46:44PM +0200, Oleg Nesterov wrote: > get_gate_vma(priv->task->mm) looks ugly and wrong, task->mm can be > NULL or it can changed by exec right after mm_access(). > > And in theory this race is not harmless, the task can exec and then > later exit and free the new mm_struct. In this case get_task_mm(oldmm) > can't help, get_gate_vma(task->mm) can read the freed/unmapped memory. > > I think that priv->task should simply die and hold_task_mempolicy() > logic can be simplified. tail_vma logic asks for cleanups too. > > Signed-off-by: Oleg Nesterov <[email protected]> > --- > fs/proc/task_mmu.c | 8 +++----- > 1 files changed, 3 insertions(+), 5 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index cfa63ee..8a5271e 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -170,7 +170,7 @@ static void *m_start(struct seq_file *m, loff_t *pos) > return mm; > down_read(&mm->mmap_sem); > > - tail_vma = get_gate_vma(priv->task->mm); > + tail_vma = get_gate_vma(mm); > priv->tail_vma = tail_vma; > hold_task_mempolicy(priv); > /* Start with last addr hint */ > @@ -351,12 +351,11 @@ static int show_map(struct seq_file *m, void *v, int > is_pid) > { > struct vm_area_struct *vma = v; > struct proc_maps_private *priv = m->private; > - struct task_struct *task = priv->task; > > show_map_vma(m, vma, is_pid); > > if (m->count < m->size) /* vma is copied successfully */ > - m->version = (vma != get_gate_vma(task->mm)) > + m->version = (vma != priv->tail_vma) > ? vma->vm_start : 0;
Drop excessive parenthesis while you're there? And in the next hunk. Otherwise: Acked-by: Kirill A. Shutemov <[email protected]> > return 0; > } > @@ -584,7 +583,6 @@ static void show_smap_vma_flags(struct seq_file *m, > struct vm_area_struct *vma) > static int show_smap(struct seq_file *m, void *v, int is_pid) > { > struct proc_maps_private *priv = m->private; > - struct task_struct *task = priv->task; > struct vm_area_struct *vma = v; > struct mem_size_stats mss; > struct mm_walk smaps_walk = { > @@ -639,7 +637,7 @@ static int show_smap(struct seq_file *m, void *v, int > is_pid) > show_smap_vma_flags(m, vma); > > if (m->count < m->size) /* vma is copied successfully */ > - m->version = (vma != get_gate_vma(task->mm)) > + m->version = (vma != priv->tail_vma) > ? vma->vm_start : 0; > return 0; > } > -- > 1.5.5.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
