netdev - Re: [PATCH v3] xfrm: Update ipcomp_scratches with NULL if not allocated

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Message-ID: <YxAyd6++6oWPu9L1@gondor.apana.org.au>
Date:   Thu, 1 Sep 2022 12:17:59 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Khalid Masum <khalid.masum.92@...il.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com,
        Steffen Klassert <steffen.klassert@...unet.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Shuah Khan <skhan@...uxfoundation.org>,
        syzbot+5ec9bb042ddfe9644773@...kaller.appspotmail.com
Subject: Re: [PATCH v3] xfrm: Update ipcomp_scratches with NULL if not
 allocated

On Thu, Sep 01, 2022 at 10:03:07AM +0600, Khalid Masum wrote:
> 
> diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c
> index cb40ff0ff28d..3774d07c5819 100644
> --- a/net/xfrm/xfrm_ipcomp.c
> +++ b/net/xfrm/xfrm_ipcomp.c
> @@ -203,6 +203,7 @@ static void ipcomp_free_scratches(void)
>  		vfree(*per_cpu_ptr(scratches, i));
>  
>  	free_percpu(scratches);
> +	ipcomp_scratches = NULL;
>  }

Good catch! This is probably the root cause of all the crashes.

>  static void * __percpu *ipcomp_alloc_scratches(void)
> @@ -215,7 +216,7 @@ static void * __percpu *ipcomp_alloc_scratches(void)
>  
>  	scratches = alloc_percpu(void *);
>  	if (!scratches)
> -		return NULL;
> +		return ipcomp_scratches = NULL;

This is unnecessary as with your first hunk, ipcomp_scratches
is guaranteed to be NULL.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt