Re: [PATCH] bpf: replace kvfree with kfree for kzalloc memory

[Eduard Zingerman]

On Mon, 2025-08-11 at 20:39 +0800, Qianfeng Rong wrote:
> The 'backedge' pointer is allocated with kzalloc(), which returns
> physically contiguous memory. Using kvfree() to deallocate such
> memory is functionally safe but semantically incorrect.
> 
> Replace kvfree() with kfree() to avoid unnecessary is_vmalloc_addr()
> check in kvfree().
> 
> Signed-off-by: Qianfeng Rong <rongqianfeng@xxxxxxxx>
> ---

Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>

>  kernel/bpf/verifier.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index c4f69a9e9af6..4e5de1ff7e30 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -19553,7 +19553,7 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
>  				err = err ?: add_scc_backedge(env, &sl->state, backedge);
>  				if (err) {
>  					free_verifier_state(&backedge->state, false);
> -					kvfree(backedge);
> +					kfree(backedge);

The backedge encapsulates verifier state, verifier states are
allocated using kzalloc() and freed using kfreed() in other places in
verifier.c => I think this patch is valid.

>  					return err;
>  				}
>  			}