linux-kernel - Re: [PATCH] netlink: Don't shift with UB on nlk->ngroups

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Message-Id: <20180730.124330.538236571439983894.davem@davemloft.net>
Date:   Mon, 30 Jul 2018 12:43:30 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dima@...sta.com
Cc:     linux-kernel@...r.kernel.org, rong.a.chen@...el.com,
        0x7f454c46@...il.com, herbert@...dor.apana.org.au,
        steffen.klassert@...unet.com, netdev@...r.kernel.org
Subject: Re: [PATCH] netlink: Don't shift with UB on nlk->ngroups

From: Dmitry Safonov <dima@...sta.com>
Date: Mon, 30 Jul 2018 18:32:36 +0100

> On i386 nlk->ngroups might be 32 or 0. Which leads to UB, resulting in
> hang during boot.
> Check for 0 ngroups and use (unsigned long long) as a type to shift.
> 
> Fixes: commit 7acf9d4237c46894e0fa0492dd96314a41742e84 ("netlink: Do not
> subscribe to non-existent groups").

Please, in the future, format your Fixes: tag correctly.  No need
to say the work "commit", please do not chop up the line no matter
how long it is, and please provide 12 digits of SHA1_ID value, rather
than the whole thing.

> Reported-by: kernel test robot <rong.a.chen@...el.com>
> Signed-off-by: Dmitry Safonov <dima@...sta.com>

Applied, thank you.