proc: task_state: read cred->group_info outside of task_lock()

task_state() reads cred->group_info under task_lock() because a long ago
it was task_struct->group_info and it was actually protected by
task->alloc_lock.  Today this task_unlock() after rcu_read_unlock() just
adds the confusion, move task_unlock() up.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Cc: Sterling Alexander <stalexan@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roland McGrath <roland@hack.frob.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 2 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index cd3653e4f35c..b5810c228c10 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -201,11 +201,10 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
                 "FDSize:\t%d\n"
                 "Groups:\t",
                 fdt ? fdt->max_fds : 0);
+        task_unlock(p);
         rcu_read_unlock();
 
         group_info = cred->group_info;
-        task_unlock(p);
-
         for (g = 0; g < group_info->ngroups; g++)
                 seq_printf(m, "%d ",
                            from_kgid_munged(user_ns, GROUP_AT(group_info, g)));