linux-kernel - Re: [V9fs-developer] [PATCH] Integer underflow in pdu

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Message-ID: <20180709193151.GI30522@ZenIV.linux.org.uk>
Date:   Mon, 9 Jul 2018 20:31:52 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Tomas Bortoli <tomasbortoli@...il.com>
Cc:     ericvh@...il.com, rminnich@...dia.gov, lucho@...kov.net,
        davem@...emloft.net, v9fs-developer@...ts.sourceforge.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller@...glegroups.com
Subject: Re: [V9fs-developer] [PATCH] Integer underflow in pdu_read()

On Mon, Jul 09, 2018 at 09:26:51PM +0200, Tomas Bortoli wrote:
> The pdu_read() function suffers from an integer underflow.
> When pdu->offset is greater than pdu->size, the length calculation will have
> a wrong result, resulting in an out-of-bound read.
> This patch modifies also pdu_write() in the same way to prevent the same
> issue from happening there and for consistency.

What does cause the calls of pdu_read() in such conditions and shouldn't *that*
be dealt with?