From 46c298cf69d0e9a27d33ff992a81bd7b441c7933 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 9 Oct 2014 15:25:19 -0700 Subject: fs/proc/task_mmu.c: don't use task->mm in m_start() and show_*map() 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 Acked-by: Kirill A. Shutemov Acked-by: Cyrill Gorcunov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) (limited to 'fs/proc') diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index c34156888d70..289dfdc0ec09 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; 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; } -- cgit v1.2.3