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[bpf-next,v2,4/5] bpf: Allow bpf_dynptr_from_skb() for tp_btf

Message ID 20240905075622.66819-5-lulie@linux.alibaba.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Allow skb dynptr for tp_btf | expand

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Commit Message

Philo Lu Sept. 5, 2024, 7:56 a.m. UTC 
Making tp_btf able to use bpf_dynptr_from_skb(), which is useful for skb
parsing, especially for non-linear paged skb data. This is achieved by
adding KF_TRUSTED_ARGS flag to bpf_dynptr_from_skb and registering it
for TRACING progs. With KF_TRUSTED_ARGS, args from fentry/fexit are
excluded, so that unsafe progs like fexit/__kfree_skb are not allowed.

We also need the skb dynptr to be read-only in tp_btf. Because
may_access_direct_pkt_data() returns false by default when checking
bpf_dynptr_from_skb, there is no need to add BPF_PROG_TYPE_TRACING to it
explicitly.

Suggested-by: Martin KaFai Lau <martin.lau@linux.dev>
Signed-off-by: Philo Lu <lulie@linux.alibaba.com>
---
 net/core/filter.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Martin KaFai Lau Sept. 6, 2024, 1:13 a.m. UTC | #1 
On 9/5/24 12:56 AM, Philo Lu wrote:
> Making tp_btf able to use bpf_dynptr_from_skb(), which is useful for skb
> parsing, especially for non-linear paged skb data. This is achieved by
> adding KF_TRUSTED_ARGS flag to bpf_dynptr_from_skb and registering it
> for TRACING progs. With KF_TRUSTED_ARGS, args from fentry/fexit are
> excluded, so that unsafe progs like fexit/__kfree_skb are not allowed.
> 
> We also need the skb dynptr to be read-only in tp_btf. Because
> may_access_direct_pkt_data() returns false by default when checking
> bpf_dynptr_from_skb, there is no need to add BPF_PROG_TYPE_TRACING to it
> explicitly.

Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
diff mbox series

Patch

diff --git a/net/core/filter.c b/net/core/filter.c
index 6d4fa9198b652..4c01f4756ddb5 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -12074,7 +12074,7 @@  int bpf_dynptr_from_skb_rdonly(struct __sk_buff *skb, u64 flags,
 }
 
 BTF_KFUNCS_START(bpf_kfunc_check_set_skb)
-BTF_ID_FLAGS(func, bpf_dynptr_from_skb)
+BTF_ID_FLAGS(func, bpf_dynptr_from_skb, KF_TRUSTED_ARGS)
 BTF_KFUNCS_END(bpf_kfunc_check_set_skb)
 
 BTF_KFUNCS_START(bpf_kfunc_check_set_xdp)
@@ -12123,6 +12123,7 @@  static int __init bpf_kfunc_init(void)
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_XMIT, &bpf_kfunc_set_skb);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_SEG6LOCAL, &bpf_kfunc_set_skb);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_NETFILTER, &bpf_kfunc_set_skb);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_kfunc_set_skb);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &bpf_kfunc_set_xdp);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
 					       &bpf_kfunc_set_sock_addr);