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

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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>
Link: https://lore.kernel.org/r/20250219161417.GA20851@redhat.com
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Oleg Nesterov 2025-02-19 17:14:17 +01:00 committed by Kees Cook
parent a3aac126ca
commit 71c769231f
1 changed files with 2 additions and 7 deletions
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9
security/yama/yama_lsm.c
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@ -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;
}