linux-kernel - Re: [PATCH 2/4] crypto: caam - fix use-after-free KASAN issue for AEAD algorithms

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Date:   Mon, 6 Apr 2020 14:04:11 +0300
From:   Horia Geantă <horia.geanta@....com>
To:     Iuliana Prodan <iuliana.prodan@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Aymen Sghaier <aymen.sghaier@....com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Silvano Di Ninno <silvano.dininno@....com>,
        Franck Lenormand <franck.lenormand@....com>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH 2/4] crypto: caam - fix use-after-free KASAN issue for
 AEAD algorithms

On 4/5/2020 2:50 PM, Iuliana Prodan wrote:
> Here's the KASAN report:
> BUG: KASAN: use-after-free in aead_crypt_done+0x60/0xd8
> Read of size 1 at addr ffff00002303f014 by task swapper/0/0
> 
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc1-00163-gd88dd5c-dirty #18
This is no a public SHA1, you are probably running with patch 1/4
applied in the tree (and with a "dirty tree").

> Hardware name: LS1046A RDB Board (DT)
> Call trace:
>  dump_backtrace+0x0/0x260
>  show_stack+0x14/0x20
>  dump_stack+0xe8/0x144
>  print_address_description.isra.11+0x64/0x348
>  __kasan_report+0x11c/0x230
>  kasan_report+0xc/0x18
>  __asan_load1+0x5c/0x68
>  aead_crypt_done+0x60/0xd8
>  caam_jr_dequeue+0x390/0x608
> ...
You should provide full KASan log - shawdow bits etc.

> @@ -973,8 +973,6 @@ static void aead_crypt_done(struct device *jrdev, u32 *desc, u32 err,
>  
>  	aead_unmap(jrdev, edesc, req);
>  
> -	kfree(edesc);
> -
>  	/*
>  	 * If no backlog flag, the completion of the request is done
>  	 * by CAAM, not crypto engine.
> @@ -983,6 +981,8 @@ static void aead_crypt_done(struct device *jrdev, u32 *desc, u32 err,
>  		aead_request_complete(req, ecode);
>  	else
>  		crypto_finalize_aead_request(jrp->engine, req, ecode);
> +
> +	kfree(edesc);
I think it's better freeing all resources before calling
the completion callback, to avoid unnecessary memory strains.

Horia