diff options
| author |   Oleg Nesterov <oleg@redhat.com> | 2014-10-09 15:25:19 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2014-10-09 22:25:48 -0400 |
| commit | 46c298cf69d0e9a27d33ff992a81bd7b441c7933 (patch) | |
| tree | 5bf50f1166996eb08fd7303ba93cc8bf8c5df7d9 /fs/proc/task_mmu.c | |
| parent | softlockup: make detector be aware of task switch of processes hogging cpu (diff) | |
| download | linux-dev-46c298cf69d0e9a27d33ff992a81bd7b441c7933.tar.xz linux-dev-46c298cf69d0e9a27d33ff992a81bd7b441c7933.zip | |
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 <oleg@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/proc/task_mmu.c')
| -rw-r--r-- | 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 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; } |