netdev - Re: [PATCH v2] netlink: do not proceed if dump's start() errs

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Message-Id: <20170930.161417.1015672612881547421.davem@davemloft.net>
Date:   Sat, 30 Sep 2017 16:14:17 +0100 (WEST)
From:   David Miller <davem@...emloft.net>
To:     johannes@...solutions.net
Cc:     Jason@...c4.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] netlink: do not proceed if dump's start() errs

From: Johannes Berg <johannes@...solutions.net>
Date: Sat, 30 Sep 2017 08:56:10 +0200

> On Thu, 2017-09-28 at 00:41 +0200, Jason A. Donenfeld wrote:
>> Drivers that use the start method for netlink dumping rely on dumpit
>> not
>> being called if start fails. For example, ila_xlat.c allocates memory
>> and assigns it to cb->args[0] in its start() function. It might fail
>> to
>> do that and return -ENOMEM instead. However, even when returning an
>> error, dumpit will be called, which, in the example above, quickly
>> dereferences the memory in cb->args[0], which will OOPS the kernel.
>> This
>> is but one example of how this goes wrong.
>> 
>> Since start() has always been a function with an int return type, it
>> therefore makes sense to use it properly, rather than ignoring it.
>> This
>> patch thus returns early and does not call dumpit() when start()
>> fails.
>> 
>> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> 
> Reviewed-by: Johannes Berg <johannes@...solutions.net>
 ...
> Either way, perhaps it's worth sending this to stable for that reason.

Agreed, applied and queued up for -stable, thanks.