From: Bernd Edlinger <bernd.edlinger@hotmail.de>
Date: Fri, 20 Mar 2020 20:27:41 +0000 (+0100)
Subject: proc: io_accounting: Use new infrastructure to fix deadlocks in execve
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=76518d3798855242817e8a8ed76b2d72f4415624;p=linux.git

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 a278fda0458bf..74f948a6b621f 100644
--- 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;
 }