* [PATCH bpf] bpf: verifier: check for packet data access based on target prog
@ 2020-08-19 1:12 Udip Pant
2020-08-19 6:03 ` Yonghong Song
0 siblings, 1 reply; 2+ messages in thread
From: Udip Pant @ 2020-08-19 1:12 UTC (permalink / raw)
To: Udip Pant, Alexei Starovoitov, Martin KaFai Lau, Song Liu,
Yonghong Song, Andrii Nakryiko, David S . Miller
Cc: netdev, bpf, linux-kernel
While using dynamic program extension (of type BPF_PROG_TYPE_EXT), we
need to check the program type of the target program to grant the read /
write access to the packet data.
The BPF_PROG_TYPE_EXT type can be used to extend types such as XDP, SKB
and others. Since the BPF_PROG_TYPE_EXT program type on itself is just a
placeholder for those, we need this extended check for those target
programs to actually work while using this option.
Tested this with a freplace xdp program. Without this patch, the
verifier fails with error 'cannot write into packet'.
Signed-off-by: Udip Pant <udippant@fb.com>
---
kernel/bpf/verifier.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ef938f17b944..4d7604430994 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2629,7 +2629,11 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
const struct bpf_call_arg_meta *meta,
enum bpf_access_type t)
{
- switch (env->prog->type) {
+ struct bpf_prog *prog = env->prog;
+ enum bpf_prog_type prog_type = prog->aux->linked_prog ?
+ prog->aux->linked_prog->type : prog->type;
+
+ switch (prog_type) {
/* Program types only with direct read access go here! */
case BPF_PROG_TYPE_LWT_IN:
case BPF_PROG_TYPE_LWT_OUT:
--
2.24.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH bpf] bpf: verifier: check for packet data access based on target prog
2020-08-19 1:12 [PATCH bpf] bpf: verifier: check for packet data access based on target prog Udip Pant
@ 2020-08-19 6:03 ` Yonghong Song
0 siblings, 0 replies; 2+ messages in thread
From: Yonghong Song @ 2020-08-19 6:03 UTC (permalink / raw)
To: Udip Pant, Alexei Starovoitov, Martin KaFai Lau, Song Liu,
Andrii Nakryiko, David S . Miller
Cc: netdev, bpf, linux-kernel
On 8/18/20 6:12 PM, Udip Pant wrote:
> While using dynamic program extension (of type BPF_PROG_TYPE_EXT), we
> need to check the program type of the target program to grant the read /
> write access to the packet data.
>
> The BPF_PROG_TYPE_EXT type can be used to extend types such as XDP, SKB
> and others. Since the BPF_PROG_TYPE_EXT program type on itself is just a
> placeholder for those, we need this extended check for those target
> programs to actually work while using this option.
>
> Tested this with a freplace xdp program. Without this patch, the
> verifier fails with error 'cannot write into packet'.
Could you add a selftest for this? FYI, current selftests/bpf have
4 freplace programs:
fexit_bpf2bpf.c:SEC("freplace/get_skb_len")
fexit_bpf2bpf.c:SEC("freplace/get_skb_ifindex")
fexit_bpf2bpf.c:SEC("freplace/get_constant")
freplace_connect4.c:SEC("freplace/do_bind")
>
> Signed-off-by: Udip Pant <udippant@fb.com>
> ---
> kernel/bpf/verifier.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index ef938f17b944..4d7604430994 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -2629,7 +2629,11 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
> const struct bpf_call_arg_meta *meta,
> enum bpf_access_type t)
> {
> - switch (env->prog->type) {
> + struct bpf_prog *prog = env->prog;
> + enum bpf_prog_type prog_type = prog->aux->linked_prog ?
> + prog->aux->linked_prog->type : prog->type;
> +
> + switch (prog_type) {
> /* Program types only with direct read access go here! */
> case BPF_PROG_TYPE_LWT_IN:
> case BPF_PROG_TYPE_LWT_OUT:
>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2020-08-19 6:04 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-08-19 1:12 [PATCH bpf] bpf: verifier: check for packet data access based on target prog Udip Pant
2020-08-19 6:03 ` Yonghong Song
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.