linux-kernel - Re: [PATCH] net: sched: Fix memory exposure from short TCA_U32

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Message-Id: <20180826.142252.1150683531522716249.davem@davemloft.net>
Date:   Sun, 26 Aug 2018 14:22:52 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     keescook@...omium.org
Cc:     linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
        jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        netdev@...r.kernel.org
Subject: Re: [PATCH] net: sched: Fix memory exposure from short TCA_U32_SEL

From: Kees Cook <keescook@...omium.org>
Date: Sat, 25 Aug 2018 22:58:01 -0700

> Via u32_change(), TCA_U32_SEL has an unspecified type in the netlink
> policy, so max length isn't enforced, only minimum. This means nkeys
> (from userspace) was being trusted without checking the actual size of
> nla_len(), which could lead to a memory over-read, and ultimately an
> exposure via a call to u32_dump(). Reachability is CAP_NET_ADMIN within
> a namespace.
> 
> Reported-by: Al Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Kees Cook <keescook@...omium.org>

I'll apply this as-is and queued it up for -stable.

If we want to avoid sizeof(*p) type stuff, it can be done as a follow-up.

Thanks.