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SubjectRe: [PATCH bpf-next v3 1/7] bpf: Refactor trampoline update code
On 04-Mär 19:37, Daniel Borkmann wrote:
> On 3/4/20 4:47 PM, KP Singh wrote:
> > From: KP Singh <kpsingh@google.com>
> >
> > As we need to introduce a third type of attachment for trampolines, the
> > flattened signature of arch_prepare_bpf_trampoline gets even more
> > complicated.
> >
> > Refactor the prog and count argument to arch_prepare_bpf_trampoline to
> > use bpf_tramp_progs to simplify the addition and accounting for new
> > attachment types.
> >
> > Signed-off-by: KP Singh <kpsingh@google.com>
> > Acked-by: Andrii Nakryiko <andriin@fb.com>
>
> [...]
> > diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
> > index c498f0fffb40..9f7e0328a644 100644
> > --- a/kernel/bpf/bpf_struct_ops.c
> > +++ b/kernel/bpf/bpf_struct_ops.c
> > @@ -320,6 +320,7 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
> > struct bpf_struct_ops_value *uvalue, *kvalue;
> > const struct btf_member *member;
> > const struct btf_type *t = st_ops->type;
> > + struct bpf_tramp_progs *tprogs = NULL;
> > void *udata, *kdata;
> > int prog_fd, err = 0;
> > void *image;
> > @@ -425,10 +426,18 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
> > goto reset_unlock;
> > }
> > + tprogs = kcalloc(BPF_TRAMP_MAX, sizeof(*tprogs), GFP_KERNEL);
> > + if (!tprogs) {
> > + err = -ENOMEM;
> > + goto reset_unlock;
> > + }
> > +
>
> Looking over the code again, I'm quite certain that here's a memleak
> since the kcalloc() is done in the for_each_member() loop in the ops
> update but then going out of scope and in the exit path we only kfree
> the last tprogs.

You're right, nice catch. Fixing it.

- KP

>
> > + tprogs[BPF_TRAMP_FENTRY].progs[0] = prog;
> > + tprogs[BPF_TRAMP_FENTRY].nr_progs = 1;
> > err = arch_prepare_bpf_trampoline(image,
> > st_map->image + PAGE_SIZE,
> > &st_ops->func_models[i], 0,
> > - &prog, 1, NULL, 0, NULL);
> > + tprogs, NULL);
> > if (err < 0)
> > goto reset_unlock;
> > @@ -469,6 +478,7 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
> > memset(uvalue, 0, map->value_size);
> > memset(kvalue, 0, map->value_size);
> > unlock:
> > + kfree(tprogs);
> > mutex_unlock(&st_map->lock);
> > return err;
> > }

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