proc: io_accounting: Use new infrastructure to fix deadlocks in execve

This changes do_io_accounting to use the new exec_update_mutex
instead of cred_guard_mutex.

This fixes possible deadlocks when the trace is accessing
/proc/$pid/io for instance.

This should be safe, as the credentials are only used for reading.

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index a278fda0458bf64e6f85168e982db9fe1bdc4b78..74f948a6b621f418c71803a2350f22a0dfade809 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2883,7 +2883,7 @@ static int do_io_accounting(struct task_struct *task, struct seq_file *m, int wh
        unsigned long flags;
        int result;
 
-       result = mutex_lock_killable(&task->signal->cred_guard_mutex);
+       result = mutex_lock_killable(&task->signal->exec_update_mutex);
        if (result)
                return result;
 
@@ -2919,7 +2919,7 @@ static int do_io_accounting(struct task_struct *task, struct seq_file *m, int wh
        result = 0;
 
 out_unlock:
-       mutex_unlock(&task->signal->cred_guard_mutex);
+       mutex_unlock(&task->signal->exec_update_mutex);
        return result;
 }