On 1/11/21 3:45 PM, Song Liu wrote:
On Jan 11, 2021, at 1:58 PM, Martin Lau <kafai@xxxxxx> wrote:
On Mon, Jan 11, 2021 at 10:35:43PM +0100, KP Singh wrote:
On Mon, Jan 11, 2021 at 7:57 PM Martin KaFai Lau <kafai@xxxxxx> wrote:
On Fri, Jan 08, 2021 at 03:19:47PM -0800, Song Liu wrote:
[ ... ]
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index dd5aedee99e73..9bd47ad2b26f1 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -140,17 +140,18 @@ static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
{
struct bpf_local_storage *local_storage;
bool free_local_storage = false;
+ unsigned long flags;
if (unlikely(!selem_linked_to_storage(selem)))
/* selem has already been unlinked from sk */
return;
local_storage = rcu_dereference(selem->local_storage);
- raw_spin_lock_bh(&local_storage->lock);
+ raw_spin_lock_irqsave(&local_storage->lock, flags);
It will be useful to have a few words in commit message on this change
for future reference purpose.
Please also remove the in_irq() check from bpf_sk_storage.c
to avoid confusion in the future. It probably should
be in a separate patch.
[ ... ]
diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index 4ef1959a78f27..f654b56907b69 100644
diff --git a/kernel/fork.c b/kernel/fork.c
index 7425b3224891d..3d65c8ebfd594 100644
[ ... ]
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -96,6 +96,7 @@
#include <linux/kasan.h>
#include <linux/scs.h>
#include <linux/io_uring.h>
+#include <linux/bpf.h>
#include <asm/pgalloc.h>
#include <linux/uaccess.h>
@@ -734,6 +735,7 @@ void __put_task_struct(struct task_struct *tsk)
cgroup_free(tsk);
task_numa_free(tsk, true);
security_task_free(tsk);
+ bpf_task_storage_free(tsk);
exit_creds(tsk);
If exit_creds() is traced by a bpf and this bpf is doing
bpf_task_storage_get(..., BPF_LOCAL_STORAGE_GET_F_CREATE),
new task storage will be created after bpf_task_storage_free().
I recalled there was an earlier discussion with KP and KP mentioned
BPF_LSM will not be called with a task that is going away.
It seems enabling bpf task storage in bpf tracing will break
this assumption and needs to be addressed?
For tracing programs, I think we will need an allow list where
task local storage can be used.
Instead of whitelist, can refcount_inc_not_zero(&tsk->usage) be used?
I think we can put refcount_inc_not_zero() in bpf_task_storage_get, like:
diff --git i/kernel/bpf/bpf_task_storage.c w/kernel/bpf/bpf_task_storage.c
index f654b56907b69..93d01b0a010e6 100644
--- i/kernel/bpf/bpf_task_storage.c
+++ w/kernel/bpf/bpf_task_storage.c
@@ -216,6 +216,9 @@ BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
* by an RCU read-side critical section.
*/
if (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {
+ if (!refcount_inc_not_zero(&task->usage))
+ return -EBUSY;
+
sdata = bpf_local_storage_update(
task, (struct bpf_local_storage_map *)map, value,
BPF_NOEXIST);
But where shall we add the refcount_dec()? IIUC, we cannot add it to
__put_task_struct().
Maybe put_task_struct()?
Thanks,
Song
