bpf: add missing NULL check for __dev_get_by_index

[PATCH] bpf: add missing NULL check for __dev_get_by_index

Posted by Qasim Ijaz 11 months, 1 week ago

The __dev_get_by_index function can return NULL if it fails to 
find a device with the provided ifindex.

We should handle this case by adding a NULL check
and cleaning up if it does happened.

Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
Fixes: a38845729ea3 ("bpf: offload: add map offload infrastructure")
---
 kernel/bpf/offload.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index a10153c3be2d..28a30fa4457a 100644
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -530,6 +530,12 @@ struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr)
 	bpf_map_init_from_attr(&offmap->map, attr);
 	rtnl_lock();
 	offmap->netdev = __dev_get_by_index(net, attr->map_ifindex);
+	if (!offmap->netdev) {
+		rtnl_unlock();
+		bpf_map_area_free(offmap);
+		return ERR_PTR(-ENODEV);
+	}	
+
 	netdev_lock_ops(offmap->netdev);
 	down_write(&bpf_devs_lock);
 	err = bpf_dev_offload_check(offmap->netdev);
-- 
2.39.5

Re: [PATCH] bpf: add missing NULL check for __dev_get_by_index

Posted by Alexei Starovoitov 11 months ago

On Sat, Mar 8, 2025 at 10:56 PM Qasim Ijaz <qasdev00@gmail.com> wrote:
>
> The __dev_get_by_index function can return NULL if it fails to
> find a device with the provided ifindex.
>
> We should handle this case by adding a NULL check
> and cleaning up if it does happened.
>
> Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
> Fixes: a38845729ea3 ("bpf: offload: add map offload infrastructure")
> ---
>  kernel/bpf/offload.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
> index a10153c3be2d..28a30fa4457a 100644
> --- a/kernel/bpf/offload.c
> +++ b/kernel/bpf/offload.c
> @@ -530,6 +530,12 @@ struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr)
>         bpf_map_init_from_attr(&offmap->map, attr);
>         rtnl_lock();
>         offmap->netdev = __dev_get_by_index(net, attr->map_ifindex);
> +       if (!offmap->netdev) {
> +               rtnl_unlock();
> +               bpf_map_area_free(offmap);
> +               return ERR_PTR(-ENODEV);
> +       }

1. you're using some old git tree.
there is no such code in bpf_map_offload_map_alloc().

2. The actual code has bpf_dev_offload_check(offmap->netdev)
that does the NULL check already.

pw-bot: cr

> +
>         netdev_lock_ops(offmap->netdev);
>         down_write(&bpf_devs_lock);
>         err = bpf_dev_offload_check(offmap->netdev);
> --
> 2.39.5
>

Re: [PATCH] bpf: add missing NULL check for __dev_get_by_index

Posted by Markus Elfring 11 months ago

…
> We should handle this case by adding a NULL check
> and cleaning up if it does happened.

Please improve such a change description another bit.

See also:
https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.14-rc5#n94

Regards,
Markus