netdev - Re: [PATCH] 9p: validate PDU length

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Message-ID: <20180725041139.GB11041@nautica>
Date:   Wed, 25 Jul 2018 06:11:39 +0200
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     Tomas Bortoli <tomasbortoli@...il.com>
Cc:     davem@...emloft.net, v9fs-developer@...ts.sourceforge.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller@...glegroups.com
Subject: Re: [PATCH] 9p: validate PDU length

Tomas Bortoli wrote on Mon, Jul 23, 2018:
> diff --git a/net/9p/client.c b/net/9p/client.c
> index 18c5271910dc..92240ccf476b 100644
> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -524,6 +525,12 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
>  	int ecode;
>  
>  	err = p9_parse_header(req->rc, NULL, &type, NULL, 0);
> +	if (req->rc->size >= c->msize) {

I was looking at this again, I think it's more appropriate to use
req->rc->capacity at this point like you did in the first version of the
patch.

I had suggested msize in the common p9_parse_header function because
that'd let us accept zc requests where the size in the pdu could be
bigger than capacity, but this isn't the case in p9_check_errors.

If you're ok with this I'll edit your commit directly, this is less work
for me than having to check a new patch.

Thanks,
-- 
Dominique