[v3,bpf-next] bpf: add a verbose message if map limit is reached

Commit Message

Anton Protopopov April 2, 2024, 7:33 a.m. UTC

When more than 64 maps are used by a program and its subprograms the
verifier returns -E2BIG. Add a verbose message which highlights the
source of the error and also print the actual limit.

v1 -> v2:
  * make the message more clear (Alexey)
v2 -> v3:
  * fixed grammar (Anton)

Signed-off-by: Anton Protopopov <[e-mail]>
Acked-by: Yonghong Song <[e-mail]>
Acked-by: John Fastabend <[e-mail]>
---
 kernel/bpf/verifier.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

Daniel Borkmann April 2, 2024, 2:19 p.m. UTC | #1

On 4/2/24 9:33 AM, Anton Protopopov wrote:
> When more than 64 maps are used by a program and its subprograms the
> verifier returns -E2BIG. Add a verbose message which highlights the
> source of the error and also print the actual limit.
> 
> v1 -> v2:
>    * make the message more clear (Alexey)
> v2 -> v3:
>    * fixed grammar (Anton)
> 
> Signed-off-by: Anton Protopopov <[e-mail]>
> Acked-by: Yonghong Song <[e-mail]>
> Acked-by: John Fastabend <[e-mail]>
> ---
>   kernel/bpf/verifier.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index edb650667f44..559526191ae7 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -18348,6 +18348,8 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
>   			}
>   
>   			if (env->used_map_cnt >= MAX_USED_MAPS) {
> +				verbose(env, "The total number of maps per program has reached the limit of %u\n",
> +					MAX_USED_MAPS);

Btw, small nit, but might make sense to streamline capitalization across
verbose() messages. Bit of a mix of small and capital letters right now
in the verifier code. Either way, independent of this one.

Cheers,
Daniel

[e-mail] April 2, 2024, 2:20 p.m. UTC | #2

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <[e-mail]>:

On Tue,  2 Apr 2024 07:33:47 +0000 you wrote:
> When more than 64 maps are used by a program and its subprograms the
> verifier returns -E2BIG. Add a verbose message which highlights the
> source of the error and also print the actual limit.
> 
> v1 -> v2:
>   * make the message more clear (Alexey)
> v2 -> v3:
>   * fixed grammar (Anton)
> 
> [...]

Here is the summary with links:
  - [v3,bpf-next] bpf: add a verbose message if map limit is reached
    https://git.kernel.org/bpf/bpf-next/c/9dc182c58b5f

You are awesome, thank you!

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index edb650667f44..559526191ae7 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -18348,6 +18348,8 @@  static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
 			}
 
 			if (env->used_map_cnt >= MAX_USED_MAPS) {
+				verbose(env, "The total number of maps per program has reached the limit of %u\n",
+					MAX_USED_MAPS);
 				fdput(f);
 				return -E2BIG;
 			}