diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2014-10-09 15:25:49 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-10-09 22:25:49 -0400 |
| commit | 47fecca15c0944924423390fe21b956eea57da30 (patch) | |
| tree | 4844cb02728511c6d4b74b11b3781330312de2a3 /fs | |
| parent | 27692cd56e2aa6924b49f4361247d707a023484a (diff) | |
fs/proc/task_nommu.c: don't use priv->task->mm
I do not know if CONFIG_PREEMPT/SMP is possible without CONFIG_MMU
but the usage of task->mm in m_stop(). The task can exit/exec before
we take mmap_sem, in this case m_stop() can hit NULL or unlock the
wrong rw_semaphore.
Also, this code uses priv->task != NULL to decide whether we need
up_read/mmput. This is correct, but we will probably kill priv->task.
Change m_start/m_stop to rely on IS_ERR_OR_NULL() like task_mmu.c does.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/proc/task_nommu.c | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c index 9019f1de3f72..429cb7a5419e 100644 --- a/fs/proc/task_nommu.c +++ b/fs/proc/task_nommu.c @@ -217,17 +217,17 @@ static void *m_start(struct seq_file *m, loff_t *pos) return ERR_PTR(-ESRCH); mm = priv->mm; - if (!mm || !atomic_inc_not_zero(&mm->mm_users)) { - put_task_struct(priv->task); - priv->task = NULL; + if (!mm || !atomic_inc_not_zero(&mm->mm_users)) return NULL; - } - down_read(&mm->mmap_sem); + down_read(&mm->mmap_sem); /* start from the Nth VMA */ for (p = rb_first(&mm->mm_rb); p; p = rb_next(p)) if (n-- == 0) return p; + + up_read(&mm->mmap_sem); + mmput(mm); return NULL; } @@ -235,11 +235,13 @@ static void m_stop(struct seq_file *m, void *_vml) { struct proc_maps_private *priv = m->private; + if (!IS_ERR_OR_NULL(_vml)) { + up_read(&priv->mm->mmap_sem); + mmput(priv->mm); + } if (priv->task) { - struct mm_struct *mm = priv->task->mm; - up_read(&mm->mmap_sem); - mmput(mm); put_task_struct(priv->task); + priv->task = NULL; } } |