On 12/19/23 3:06 AM, Simon Horman wrote:
On Mon, Dec 18, 2023 at 12:18:20PM +0800, D. Wythe wrote:
From: "D. Wythe" <alibuda@xxxxxxxxxxxxxxxxx>
To support the prog update, we need to ensure that the prog seen
within the hook is always valid. Considering that hooks are always
protected by rcu_read_lock(), which provide us the ability to
access the prog under rcu.
Signed-off-by: D. Wythe <alibuda@xxxxxxxxxxxxxxxxx>
...
@@ -26,8 +17,20 @@ struct bpf_nf_link {
struct net *net;
u32 dead;
const struct nf_defrag_hook *defrag_hook;
+ struct rcu_head head;
};
+static unsigned int nf_hook_run_bpf(void *bpf_link, struct sk_buff *skb,
+ const struct nf_hook_state *s)
+{
+ const struct bpf_nf_link *nf_link = bpf_link;
+ struct bpf_nf_ctx ctx = {
+ .state = s,
+ .skb = skb,
+ };
+ return bpf_prog_run(rcu_dereference(nf_link->link.prog), &ctx);
Hi,
AFAICT nf_link->link.prog isn't annotated as __rcu,
so perhaps rcu_dereference() is not correct here?
In any case, sparse seems a bit unhappy:
.../nf_bpf_link.c:31:29: error: incompatible types in comparison expression (different address spaces):
.../nf_bpf_link.c:31:29: struct bpf_prog [noderef] __rcu *
.../nf_bpf_link.c:31:29: struct bpf_prog *
Hi Simon,
thanks for the reporting.
Yes, I had anticipated that sparse would report an error. I tried to
cast the type,
but it would compile an error likes that:
net/netfilter/nf_bpf_link.c: In function ‘nf_hook_run_bpf’:
./include/asm-generic/rwonce.h:44:70: error: lvalue required as unary
‘&’ operand
44 | #define __READ_ONCE(x) (*(const volatile
__unqual_scalar_typeof(x) *)&(x))
| ^
./include/asm-generic/rwonce.h:50:2: note: in expansion of macro
‘__READ_ONCE’
50 | __READ_ONCE(x); \
| ^~~~~~~~~~~
./include/linux/rcupdate.h:436:43: note: in expansion of macro ‘READ_ONCE’
436 | typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \
| ^~~~~~~~~
./include/linux/rcupdate.h:584:2: note: in expansion of macro
‘__rcu_dereference_check’
584 | __rcu_dereference_check((p), __UNIQUE_ID(rcu), \
| ^~~~~~~~~~~~~~~~~~~~~~~
./include/linux/rcupdate.h:656:28: note: in expansion of macro
‘rcu_dereference_check’
656 | #define rcu_dereference(p) rcu_dereference_check(p, 0)
| ^~~~~~~~~~~~~~~~~~~~~
net/netfilter/nf_bpf_link.c:31:22: note: in expansion of macro
‘rcu_dereference’
31 | return bpf_prog_run(rcu_dereference((const struct bpf_prog
__rcu *)nf_link->link.prog), &ctx);
| ^~~~~~~~~~~~~~~
So, I think we might need to go back to version 1.
@ Florian , what do you think ?
D. Wythe
+}
+
#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4) || IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
static const struct nf_defrag_hook *
get_proto_defrag_hook(struct bpf_nf_link *link,
...
