Re: [PATCH] hsr: fix NULL pointer dereference in skb_clone with hw tag insertion

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Nov 26, 2025 at 02:31:58AM +0530, ssrane_b23@ee.vjti.ac.in wrote:
> From: Shaurya Rane <ssrane_b23@ee.vjti.ac.in>
> 
> When hardware HSR tag insertion is enabled (NETIF_F_HW_HSR_TAG_INS) and
> frame->skb_std is NULL, both hsr_create_tagged_frame() and
> prp_create_tagged_frame() will call skb_clone() with a NULL skb pointer,
> causing a kernel crash.
> 
> Fix this by adding NULL checks for frame->skb_std before calling
> skb_clone() in the functions.
> 
> Reported-by: syzbot+2fa344348a579b779e05@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=2fa344348a579b779e05
> Fixes: f266a683a480 ("net/hsr: Better frame dispatch")
> Signed-off-by: Shaurya Rane <ssrane_b23@ee.vjti.ac.in>
> ---
>  net/hsr/hsr_forward.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c
> index 339f0d220212..4c1a311b900f 100644
> --- a/net/hsr/hsr_forward.c
> +++ b/net/hsr/hsr_forward.c
> @@ -211,6 +211,9 @@ struct sk_buff *prp_get_untagged_frame(struct hsr_frame_info *frame,
>  				  __FILE__, __LINE__, port->dev->name);
>  			return NULL;
>  		}
> +
> +		if (!frame->skb_std)
> +			return NULL;
>  	}
>  
>  	return skb_clone(frame->skb_std, GFP_ATOMIC);
> @@ -341,6 +344,8 @@ struct sk_buff *hsr_create_tagged_frame(struct hsr_frame_info *frame,
>  		hsr_set_path_id(frame, hsr_ethhdr, port);
>  		return skb_clone(frame->skb_hsr, GFP_ATOMIC);
>  	} else if (port->dev->features & NETIF_F_HW_HSR_TAG_INS) {
> +		if (!frame->skb_std)
> +			return NULL;
>  		return skb_clone(frame->skb_std, GFP_ATOMIC);
>  	}
>  
> @@ -385,6 +390,8 @@ struct sk_buff *prp_create_tagged_frame(struct hsr_frame_info *frame,
>  		}
>  		return skb_clone(frame->skb_prp, GFP_ATOMIC);
>  	} else if (port->dev->features & NETIF_F_HW_HSR_TAG_INS) {
> +		if (!frame->skb_std)
> +			return NULL;
>  		return skb_clone(frame->skb_std, GFP_ATOMIC);
>  	}
>  
> -- 
> 2.34.1
> 
> 
Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
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thanks,

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