[PATCH 3/4] proc: io_accounting: Use new infrastructure to fix deadlocks in execve

Bernd Edlinger
2020-03-10T17:45:57Z

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>
---
fs/proc/base.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 4fdfe4f..529d0c6 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2770,7 +2770,7 @@ 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;

@@ -2806,7 +2806,7 @@ 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;
}

--
1.9.1