linux-kernel - Re: [PATCH] net: qrtr: fix OOB Read in qrtr_endpoint

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Date:   Mon, 14 Jun 2021 10:57:45 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     mani@...nel.org, davem@...emloft.net,
        linux-arm-msm@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        syzbot+1917d778024161609247@...kaller.appspotmail.com
Subject: Re: [PATCH] net: qrtr: fix OOB Read in qrtr_endpoint_post

On Mon 14 Jun 07:06 CDT 2021, Pavel Skripkin wrote:

> Syzbot reported slab-out-of-bounds Read in
> qrtr_endpoint_post. The problem was in wrong
> _size_ type:
> 
> 	if (len != ALIGN(size, 4) + hdrlen)
> 		goto err;
> 
> If size from qrtr_hdr is 4294967293 (0xfffffffd), the result of
> ALIGN(size, 4) will be 0. In case of len == hdrlen and size == 4294967293
> in header this check won't fail and
> 
> 	skb_put_data(skb, data + hdrlen, size);
> 
> will read out of bound from data, which is hdrlen allocated block.
> 
> Fixes: 194ccc88297a ("net: qrtr: Support decoding incoming v2 packets")
> Reported-and-tested-by: syzbot+1917d778024161609247@...kaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin@...il.com>

Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>

Regards,
Bjorn

> ---
>  net/qrtr/qrtr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c
> index c0477bec09bd..f2efaa4225f9 100644
> --- a/net/qrtr/qrtr.c
> +++ b/net/qrtr/qrtr.c
> @@ -436,7 +436,7 @@ int qrtr_endpoint_post(struct qrtr_endpoint *ep, const void *data, size_t len)
>  	struct qrtr_sock *ipc;
>  	struct sk_buff *skb;
>  	struct qrtr_cb *cb;
> -	unsigned int size;
> +	size_t size;
>  	unsigned int ver;
>  	size_t hdrlen;
>  
> -- 
> 2.32.0
>