[PATCH 1/4] kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve

Bernd Edlinger
2020-03-10T17:45:18Z

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

This should be safe, as the credentials are only used for reading,
and furthermore ->mm and ->sighand are updated on execve,
but only under the new exec_update_mutex.

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
---
kernel/kcmp.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/kcmp.c b/kernel/kcmp.c
index a0e3d7a..b3ff928 100644
--- a/kernel/kcmp.c
+++ b/kernel/kcmp.c
@@ -173,8 +173,8 @@ static int kcmp_epoll_target(struct task_struct *task1,
/*
* One should have enough rights to inspect task details.
*/
- ret = kcmp_lock(&task1->signal->cred_guard_mutex,
- &task2->signal->cred_guard_mutex);
+ ret = kcmp_lock(&task1->signal->exec_update_mutex,
+ &task2->signal->exec_update_mutex);
if (ret)
goto err;
if (!ptrace_may_access(task1, PTRACE_MODE_READ_REALCREDS) ||
@@ -229,8 +229,8 @@ static int kcmp_epoll_target(struct task_struct *task1,
}

err_unlock:
- kcmp_unlock(&task1->signal->cred_guard_mutex,
- &task2->signal->cred_guard_mutex);
+ kcmp_unlock(&task1->signal->exec_update_mutex,
+ &task2->signal->exec_update_mutex);
err:
put_task_struct(task1);
put_task_struct(task2);
--
1.9.1