linux-kernel - Re: NULL deref in drivers/md/dm-crypt.c:crypt

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Date:	Sun, 06 Feb 2011 23:50:11 +0100
From:	Milan Broz <mbroz@...hat.com>
To:	Jesper Juhl <jj@...osbits.net>
CC:	linux-kernel@...r.kernel.org, Alexander Kjeldaas <astor@...t.no>,
	David Woodhouse <David.Woodhouse@...el.com>,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: NULL deref in drivers/md/dm-crypt.c:crypt_convert()

On 02/06/2011 11:31 PM, Jesper Juhl wrote:
> The coverity checker found this. I don't know how to fix it, so I'll just 
> report it and hope that someone else can address the issue.

Hi,
can I see the plain output from the coverity check somewhere?

> 
> In drivers/md/dm-crypt.c:crypt_convert() we have this code:
> ...
>   		while(ctx->idx_in < ctx->bio_in->bi_vcnt &&
>   		      ctx->idx_out < ctx->bio_out->bi_vcnt) {
>   	
>   			crypt_alloc_req(cc, ctx);

Here in crypt_alloc_req() you have:

	struct crypt_cpu *this_cc = this_crypt_config(cc);
	if (!this_cc->req)
		this_cc->req = mempool_alloc(cc->req_pool, GFP_NOIO);

>   	
>   			atomic_inc(&ctx->pending);
>   	
>   			r = crypt_convert_block(cc, ctx, this_cc->req);

this_cc is: struct crypt_cpu *this_cc = this_crypt_config(cc);
and because it is always running on the same CPU, 
this_cc->req cannot be NULL here, because it was allocated
in crypt_alloc_req().

It is false positive here.

Milan
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