On 04-Mär 19:37, Daniel Borkmann wrote:

On 3/4/20 4:47 PM, KP Singh wrote:

quoted

From: KP Singh <redacted>

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 <redacted>
Acked-by: Andrii Nakryiko <redacted>

[...]

quoted

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

quoted

+		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;
  }