[v6,12/16] proc: io_accounting: Use new infrastructure to fix deadlocks in execve

Commit Message

Bernd Edlinger March 20, 2020, 8:27 p.m. UTC

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

Patch

diff --git a/fs/proc/base.c b/fs/proc/base.c
index fed76abf..6b13fc4 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2861,7 +2861,7 @@  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;
 
@@ -2897,7 +2897,7 @@  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;
 }