Re: [PATCH bpf-next] bpf: Check IS_ERR for the bpf_map_get() return value

[Stanislav Fomichev <sdf@google.com>]

On 03/24, Martin KaFai Lau wrote:
> From: Martin KaFai Lau <martin.lau@kernel.org>

> This patch fixes a mistake in checking NULL instead of
> checking IS_ERR for the bpf_map_get() return value.

> It also fixes the return value in link_update_map() from -EINVAL
> to PTR_ERR(*_map).

> Reported-by: syzbot+71ccc0fe37abb458406b@syzkaller.appspotmail.com
> Fixes: 68b04864ca42 ("bpf: Create links for BPF struct_ops maps.")
> Fixes: aef56f2e918b ("bpf: Update the struct_ops of a bpf_link.")
> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

Acked-by: Stanislav Fomichev <sdf@google.com>

> ---
>   kernel/bpf/bpf_struct_ops.c | 4 ++--
>   kernel/bpf/syscall.c        | 4 ++--
>   2 files changed, 4 insertions(+), 4 deletions(-)

> diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
> index 6401deca3b56..d3f0a4825fa6 100644
> --- a/kernel/bpf/bpf_struct_ops.c
> +++ b/kernel/bpf/bpf_struct_ops.c
> @@ -871,8 +871,8 @@ int bpf_struct_ops_link_create(union bpf_attr *attr)
>   	int err;

>   	map = bpf_map_get(attr->link_create.map_fd);
> -	if (!map)
> -		return -EINVAL;
> +	if (IS_ERR(map))
> +		return PTR_ERR(map);

>   	st_map = (struct bpf_struct_ops_map *)map;

> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index b4d758fa5981..a09597c95029 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -4689,12 +4689,12 @@ static int link_update_map(struct bpf_link *link,  
> union bpf_attr *attr)

>   	new_map = bpf_map_get(attr->link_update.new_map_fd);
>   	if (IS_ERR(new_map))
> -		return -EINVAL;
> +		return PTR_ERR(new_map);

>   	if (attr->link_update.flags & BPF_F_REPLACE) {
>   		old_map = bpf_map_get(attr->link_update.old_map_fd);
>   		if (IS_ERR(old_map)) {
> -			ret = -EINVAL;
> +			ret = PTR_ERR(old_map);
>   			goto out_put;
>   		}
>   	} else if (attr->link_update.old_map_fd) {
> --
> 2.34.1