linux-kernel - Re: [PATCHv2] netlink: Don't shift on 64 for ngroups

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Message-Id: <20180804.175342.887624852314321631.davem@davemloft.net>
Date:   Sat, 04 Aug 2018 17:53:42 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dima@...sta.com
Cc:     linux-kernel@...r.kernel.org, natechancellor@...il.com,
        herbert@...dor.apana.org.au, steffen.klassert@...unet.com,
        netdev@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCHv2] netlink: Don't shift on 64 for ngroups

From: Dmitry Safonov <dima@...sta.com>
Date: Sun,  5 Aug 2018 01:35:53 +0100

> It's legal to have 64 groups for netlink_sock.
> 
> As user-supplied nladdr->nl_groups is __u32, it's possible to subscribe
> only to first 32 groups.
> 
> The check for correctness of .bind() userspace supplied parameter
> is done by applying mask made from ngroups shift. Which broke Android
> as they have 64 groups and the shift for mask resulted in an overflow.
> 
> Fixes: 61f4b23769f0 ("netlink: Don't shift with UB on nlk->ngroups")
> Reported-and-Tested-by: Nathan Chancellor <natechancellor@...il.com>
> Signed-off-by: Dmitry Safonov <dima@...sta.com>

Applied and queued up for -stable.