From: Hou Tao <houtao1@xxxxxxxxxx>
Three callers of bpf_task_storage_lock() are ->map_lookup_elem,
->map_update_elem, ->map_delete_elem from bpf syscall. BPF syscall for
these three operations of task storage has already disabled migration.
Another two callers are bpf_task_storage_get() and
bpf_task_storage_delete() helpers which will be used by BPF program.
Two callers of bpf_task_storage_trylock() are bpf_task_storage_get() and
bpf_task_storage_delete() helpers. The running contexts of these helpers
have already disabled migration.
Therefore, it is safe to remove migrate_{disable|enable} from task
storage lock helpers for these call sites. However,
bpf_task_storage_free() also invokes bpf_task_storage_lock() and its
running context doesn't disable migration, therefore, add the missed
migrate_{disable|enable} in bpf_task_storage_free().
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
kernel/bpf/bpf_task_storage.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index bf7fa15fdcc6c..1109475953c01 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -24,22 +24,20 @@ static DEFINE_PER_CPU(int, bpf_task_storage_busy);
static void bpf_task_storage_lock(void)
{
- migrate_disable();
+ cant_migrate();
this_cpu_inc(bpf_task_storage_busy);
}
static void bpf_task_storage_unlock(void)
{
this_cpu_dec(bpf_task_storage_busy);
- migrate_enable();
}
static bool bpf_task_storage_trylock(void)
{
- migrate_disable();
+ cant_migrate();
if (unlikely(this_cpu_inc_return(bpf_task_storage_busy) != 1)) {
this_cpu_dec(bpf_task_storage_busy);
- migrate_enable();
return false;
}
return true;
@@ -72,18 +70,19 @@ void bpf_task_storage_free(struct task_struct *task)
{
struct bpf_local_storage *local_storage;
+ migrate_disable();
rcu_read_lock();
local_storage = rcu_dereference(task->bpf_storage);
- if (!local_storage) {
- rcu_read_unlock();
- return;
- }
+ if (!local_storage)
+ goto out;
bpf_task_storage_lock();
bpf_local_storage_destroy(local_storage);
bpf_task_storage_unlock();
+out:
rcu_read_unlock();
+ migrate_enable();
}
static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key)
--
2.29.2
