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

BugLink: https://bugs.launchpad.net/bugs/1900624
[ Upstream commit 76518d3798855242817e8a8ed76b2d72f4415624 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 7139128031476d581ab3572802946bcfaca37e9f..8297b137ea72fba68c569e3d05a08c980487212f 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2784,7 +2784,7 @@ 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;
 
@@ -2820,7 +2820,7 @@ 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;
 }