[PATCH] yama: don't abuse rcu_read_lock/get_task_struct in yama_task_prctl()

Oleg Nesterov
2025-02-19T16:14:56Z

current->group_leader is stable, no need to take rcu_read_lock() and do
get/put_task_struct().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
security/yama/yama_lsm.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 1971710620c1..3d064dd4e03f 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -222,7 +222,7 @@ static int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
unsigned long arg4, unsigned long arg5)
{
int rc = -ENOSYS;
- struct task_struct *myself = current;
+ struct task_struct *myself;

switch (option) {
case PR_SET_PTRACER:
@@ -232,11 +232,7 @@ static int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
* leader checking is handled later when walking the ancestry
* at the time of PTRACE_ATTACH check.
*/
- rcu_read_lock();
- if (!thread_group_leader(myself))
- myself = rcu_dereference(myself->group_leader);
- get_task_struct(myself);
- rcu_read_unlock();
+ myself = current->group_leader;

if (arg2 == 0) {
yama_ptracer_del(NULL, myself);
@@ -255,7 +251,6 @@ static int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
}
}

- put_task_struct(myself);
break;
}

--
2.25.1.362.g51ebf55