linux-kernel - Re: [PATCH 4.19 01/51] ethtool: fix potential userspace buffer overflow

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190610084229.GA31797@unicorn.suse.cz>
Date:   Mon, 10 Jun 2019 10:42:29 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     stable@...r.kernel.org
Cc:     Pavel Machek <pavel@...x.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 4.19 01/51] ethtool: fix potential userspace buffer
 overflow

On Mon, Jun 10, 2019 at 10:21:12AM +0200, Pavel Machek wrote:
> Hi!
> 
> > From: Vivien Didelot <vivien.didelot@...il.com>
> > 
> > [ Upstream commit 0ee4e76937d69128a6a66861ba393ebdc2ffc8a2 ]
> > 
> > ethtool_get_regs() allocates a buffer of size ops->get_regs_len(),
> > and pass it to the kernel driver via ops->get_regs() for filling.
> > 
> > There is no restriction about what the kernel drivers can or cannot do
> > with the open ethtool_regs structure. They usually set regs->version
> > and ignore regs->len or set it to the same size as ops->get_regs_len().
> > 
> > But if userspace allocates a smaller buffer for the registers dump,
> > we would cause a userspace buffer overflow in the final copy_to_user()
> > call, which uses the regs.len value potentially reset by the driver.
> > 
> > To fix this, make this case obvious and store regs.len before calling
> > ops->get_regs(), to only copy as much data as requested by userspace,
> > up to the value returned by ops->get_regs_len().
> > 
> > While at it, remove the redundant check for non-null regbuf.
> 
> Mainline differs from 4.19-stable here, and while the non-null check
> is redundant in -mainline, it does not seem to be redundant in
> -stable.
> 
> In stable, if get_regs_len() returns < 0, we'll pass it to vzalloc.

Right. :-(

I guess we should also pick commit f9fc54d313fa ("ethtool: check the
return value of get_regs_len") to stable branches before 5.0.

Michal