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 <[email protected]> --- 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 003f2be..e0237c1 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; } } -- 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/
