diff mbox series

[bpf,1/2] bpf: enforce that struct_ops programs be GPL-only

Message ID 20210325154034.85346-1-toke@redhat.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series [bpf,1/2] bpf: enforce that struct_ops programs be GPL-only | expand

Checks

Context Check Description
netdev/cover_letter success Link
netdev/fixes_present success Link
netdev/patch_count success Link
netdev/tree_selection success Clearly marked for bpf
netdev/subject_prefix success Link
netdev/cc_maintainers success CCed 10 of 10 maintainers
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 17 this patch: 17
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success Link
netdev/checkpatch warning WARNING: line length of 89 exceeds 80 columns
netdev/build_allmodconfig_warn success Errors and warnings before: 17 this patch: 17
netdev/header_inline success Link

Commit Message

Toke Høiland-Jørgensen March 25, 2021, 3:40 p.m. UTC
With the introduction of the struct_ops program type, it became possible to
implement kernel functionality in BPF, making it viable to use BPF in place
of a regular kernel module for these particular operations.

Thus far, the only user of this mechanism is for implementing TCP
congestion control algorithms. These are clearly marked as GPL-only when
implemented as modules (as seen by the use of EXPORT_SYMBOL_GPL for
tcp_register_congestion_control()), so it seems like an oversight that this
was not carried over to BPF implementations. And sine this is the only user
of the struct_ops mechanism, just enforcing GPL-only for the struct_ops
program type seems like the simplest way to fix this.

Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 kernel/bpf/verifier.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Martin KaFai Lau March 25, 2021, 6:15 p.m. UTC | #1
On Thu, Mar 25, 2021 at 04:40:33PM +0100, Toke Høiland-Jørgensen wrote:
> With the introduction of the struct_ops program type, it became possible to
> implement kernel functionality in BPF, making it viable to use BPF in place
> of a regular kernel module for these particular operations.
> 
> Thus far, the only user of this mechanism is for implementing TCP
> congestion control algorithms. These are clearly marked as GPL-only when
> implemented as modules (as seen by the use of EXPORT_SYMBOL_GPL for
> tcp_register_congestion_control()), so it seems like an oversight that this
> was not carried over to BPF implementations. And sine this is the only user
> of the struct_ops mechanism, just enforcing GPL-only for the struct_ops
> program type seems like the simplest way to fix this.
> 
> Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf")
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> ---
>  kernel/bpf/verifier.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 44e4ec1640f1..48dd0c0f087c 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -12166,6 +12166,11 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
>  		return -ENOTSUPP;
>  	}
>  
> +	if (!prog->gpl_compatible) {
> +		verbose(env, "struct ops programs must have a GPL compatible license\n");
> +		return -EINVAL;
> +	}
> +
Thanks for the patch.

A nit.  Instead of sitting in between of the attach_btf_id check
and expected_attach_type check, how about moving it to the beginning
of this function.  Checking attach_btf_id and expected_attach_type
would make more sense to be done next to each other as in the current
code.

Acked-by: Martin KaFai Lau <kafai@fb.com>
Toke Høiland-Jørgensen March 25, 2021, 8:37 p.m. UTC | #2
Martin KaFai Lau <kafai@fb.com> writes:

> On Thu, Mar 25, 2021 at 04:40:33PM +0100, Toke Høiland-Jørgensen wrote:
>> With the introduction of the struct_ops program type, it became possible to
>> implement kernel functionality in BPF, making it viable to use BPF in place
>> of a regular kernel module for these particular operations.
>> 
>> Thus far, the only user of this mechanism is for implementing TCP
>> congestion control algorithms. These are clearly marked as GPL-only when
>> implemented as modules (as seen by the use of EXPORT_SYMBOL_GPL for
>> tcp_register_congestion_control()), so it seems like an oversight that this
>> was not carried over to BPF implementations. And sine this is the only user
>> of the struct_ops mechanism, just enforcing GPL-only for the struct_ops
>> program type seems like the simplest way to fix this.
>> 
>> Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf")
>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
>> ---
>>  kernel/bpf/verifier.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>> 
>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
>> index 44e4ec1640f1..48dd0c0f087c 100644
>> --- a/kernel/bpf/verifier.c
>> +++ b/kernel/bpf/verifier.c
>> @@ -12166,6 +12166,11 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
>>  		return -ENOTSUPP;
>>  	}
>>  
>> +	if (!prog->gpl_compatible) {
>> +		verbose(env, "struct ops programs must have a GPL compatible license\n");
>> +		return -EINVAL;
>> +	}
>> +
> Thanks for the patch.
>
> A nit.  Instead of sitting in between of the attach_btf_id check
> and expected_attach_type check, how about moving it to the beginning
> of this function.  Checking attach_btf_id and expected_attach_type
> would make more sense to be done next to each other as in the current
> code.

Yeah, good point. Not sure what I was thinking stuffing it in the middle
there; will fix and send a v2!

> Acked-by: Martin KaFai Lau <kafai@fb.com>

Thanks! :)

-Toke
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 44e4ec1640f1..48dd0c0f087c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -12166,6 +12166,11 @@  static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
 		return -ENOTSUPP;
 	}
 
+	if (!prog->gpl_compatible) {
+		verbose(env, "struct ops programs must have a GPL compatible license\n");
+		return -EINVAL;
+	}
+
 	t = st_ops->type;
 	member_idx = prog->expected_attach_type;
 	if (member_idx >= btf_type_vlen(t)) {