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kernel: allowlist: escape persistent_allow_list to kthread #3454

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kernel: allowlist: escape persistent_allow_list to kthread #3454

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50 changes: 23 additions & 27 deletions kernel/policy/allowlist.c
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
#include <linux/compiler_types.h>
#include <linux/hashtable.h>
#include <linux/kref.h>
#include <linux/kthread.h>

#include "klog.h" // IWYU pragma: keep
#include "ksu.h"
Expand Down Expand Up @@ -423,8 +424,7 @@ bool ksu_get_allow_list(int *array, u16 length, u16 *out_length, u16 *out_total,
return true;
}

// TODO: move to kernel thread or work queue
static void do_persistent_allow_list(struct callback_head *_cb)
static inline void do_persistent_allow_list()
{
u32 magic = FILE_MAGIC;
u32 version = FILE_FORMAT_VERSION;
Expand All @@ -450,48 +450,44 @@ static void do_persistent_allow_list(struct callback_head *_cb)
goto close_file;
}

mutex_lock(&allowlist_mutex);
hash_for_each (allow_list, i, p, list) {
pr_info("save allow list, name: %s uid :%d, allow: %d\n", p->profile.key, p->profile.curr_uid,
p->profile.allow_su);

kernel_write(fp, &p->profile, sizeof(p->profile), &off);
}
mutex_unlock(&allowlist_mutex);

close_file:
filp_close(fp, 0);
out:
revert_creds(saved);
kfree(_cb);
}

void ksu_persistent_allow_list()
static int persistent_allow_list_pre(void *data)
{
struct task_struct *tsk;
if (IS_ENABLED(CONFIG_KSU_DEBUG)
pr_info("do_persistent_allow_list: pid: %d started\n", current->pid);

/*
* repurpose the mutex that was inside do_persistent_allow_list
* this way we get a single instance access.
* however, there is no need for mutex_trylock-fail-ret pattern for this one
* we just let other threads to wait-stall
*
*/
mutex_lock(&allowlist_mutex);
do_persistent_allow_list();
mutex_unlock(&allowlist_mutex);

rcu_read_lock();
tsk = get_pid_task(find_vpid(1), PIDTYPE_PID);
if (!tsk) {
rcu_read_unlock();
pr_err("save_allow_list find init task err\n");
return;
}
rcu_read_unlock();
if (IS_ENABLED(CONFIG_KSU_DEBUG)
pr_info("do_persistent_allow_list: pid: %d exit\n", current->pid);

struct callback_head *cb = kzalloc(sizeof(struct callback_head), GFP_KERNEL);
if (!cb) {
pr_err("save_allow_list alloc cb err\b");
goto put_task;
}
cb->func = do_persistent_allow_list;
if (task_work_add(tsk, cb, TWA_RESUME)) {
kfree(cb);
pr_warn("save_allow_list add task_work failed\n");
}
return 0;
}

put_task:
put_task_struct(tsk);
void ksu_persistent_allow_list()
{
kthread_run(persistent_allow_list_pre, NULL, "allowlist");
}

void ksu_load_allow_list()
Expand Down