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-rw-r--r--fs/proc/base.c23
1 files changed, 11 insertions, 12 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 3ce5ae9e3d2d..917f338a6739 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -237,20 +237,19 @@ struct mm_struct *mm_for_maps(struct task_struct *task)
struct mm_struct *mm = get_task_mm(task);
if (!mm)
return NULL;
+ if (mm != current->mm) {
+ /*
+ * task->mm can be changed before security check,
+ * in that case we must notice the change after.
+ */
+ if (!ptrace_may_access(task, PTRACE_MODE_READ) ||
+ mm != task->mm) {
+ mmput(mm);
+ return NULL;
+ }
+ }
down_read(&mm->mmap_sem);
- task_lock(task);
- if (task->mm != mm)
- goto out;
- if (task->mm != current->mm &&
- __ptrace_may_access(task, PTRACE_MODE_READ) < 0)
- goto out;
- task_unlock(task);
return mm;
-out:
- task_unlock(task);
- up_read(&mm->mmap_sem);
- mmput(mm);
- return NULL;
}
static int proc_pid_cmdline(struct task_struct *task, char * buffer)