linux-kernel - Re: [PATCH] bpf: fix possible uninitialized access in inactive rotation

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Message-ID: <582C828A.60605@iogearbox.net>
Date:   Wed, 16 Nov 2016 17:00:10 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Arnd Bergmann <arnd@...db.de>, Alexei Starovoitov <ast@...nel.org>
CC:     Martin KaFai Lau <kafai@...com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bpf: fix possible uninitialized access in inactive rotation

On 11/16/2016 03:38 PM, Arnd Bergmann wrote:
> This newly added code causes a build warning:
>
> kernel/bpf/bpf_lru_list.c: In function '__bpf_lru_list_rotate_inactive':
> kernel/bpf/bpf_lru_list.c:201:28: error: 'next' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>
> The warning is plausible from looking at the code, though there might
> be non-obvious external constraints that ensure it always works.
>
> Moving the assignment of ->next_inactive_rotation inside of the
> loop makes it obvious to the reader and the compiler when we
> actually want to update ->next.
>
> Fixes: 3a08c2fd7634 ("bpf: LRU List")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks a lot, Arnd, patch was already sent here though:

http://patchwork.ozlabs.org/patch/695202/