Fix race in process_vm_rw_core

This fixes the race in process_vm_core found by Oleg (see

  http://article.gmane.org/gmane.linux.kernel/1235667/

for details).

This has been updated since I last sent it as the creation of the new
mm_access() function did almost exactly the same thing as parts of the
previous version of this patch did.

In order to use mm_access() even when /proc isn't enabled, we move it to
kernel/fork.c where other related process mm access functions already
are.

Signed-off-by: Chris Yeoh <yeohc@au1.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 20 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index d9512bd03e6c..d4548dd49b02 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -198,26 +198,6 @@ static int proc_root_link(struct dentry *dentry, struct path *path)
         return result;
 }
 
-static struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
-{
-        struct mm_struct *mm;
-        int err;
-
-        err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
-        if (err)
-                return ERR_PTR(err);
-
-        mm = get_task_mm(task);
-        if (mm && mm != current->mm &&
-                        !ptrace_may_access(task, mode)) {
-                mmput(mm);
-                mm = ERR_PTR(-EACCES);
-        }
-        mutex_unlock(&task->signal->cred_guard_mutex);
-
-        return mm;
-}
-
 struct mm_struct *mm_for_maps(struct task_struct *task)
 {
         return mm_access(task, PTRACE_MODE_READ);