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Message-ID: <43822f54-cc0b-4ac7-814c-502f6f995c28@blackwall.org>
Date: Tue, 27 Feb 2024 14:48:59 +0200
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Subject: Re: [PATCH net v2] rtnetlink: fix error logic of IFLA_BRIDGE_FLAGS
 writing back
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To: Lin Ma <linma@zju.edu.cn>, davem@davemloft.net, edumazet@google.com,
 kuba@kernel.org, pabeni@redhat.com, idosch@nvidia.com, jiri@resnulli.us,
 lucien.xin@gmail.com, edwin.peer@broadcom.com, amcohen@nvidia.com,
 pctammela@mojatatu.com, liuhangbin@gmail.com, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org
References: <20240227121128.608110-1-linma@zju.edu.cn>
From: Nikolay Aleksandrov <razor@blackwall.org>
In-Reply-To: <20240227121128.608110-1-linma@zju.edu.cn>
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On 2/27/24 14:11, Lin Ma wrote:
> In the commit d73ef2d69c0d ("rtnetlink: let rtnl_bridge_setlink checks
> IFLA_BRIDGE_MODE length"), an adjustment was made to the old loop logic
> in the function `rtnl_bridge_setlink` to enable the loop to also check
> the length of the IFLA_BRIDGE_MODE attribute. However, this adjustment
> removed the `break` statement and led to an error logic of the flags
> writing back at the end of this function.
> 
> if (have_flags)
>      memcpy(nla_data(attr), &flags, sizeof(flags));
>      // attr should point to IFLA_BRIDGE_FLAGS NLA !!!
> 
> Before the mentioned commit, the `attr` is granted to be IFLA_BRIDGE_FLAGS.
> However, this is not necessarily true fow now as the updated loop will let
> the attr point to the last NLA, even an invalid NLA which could cause
> overflow writes.
> 
> This patch introduces a new variable `br_flag` to save the NLA pointer
> that points to IFLA_BRIDGE_FLAGS and uses it to resolve the mentioned
> error logic.
> 
> Fixes: d73ef2d69c0d ("rtnetlink: let rtnl_bridge_setlink checks IFLA_BRIDGE_MODE length")
> Signed-off-by: Lin Ma <linma@zju.edu.cn>
> ---
> v1 -> v2: rename the br_flag to br_flags_attr which offers better
>            description suggested by Nikolay.
> 
>   net/core/rtnetlink.c | 11 +++++------
>   1 file changed, 5 insertions(+), 6 deletions(-)
> 

As Jiri pointed out, you should wait a day before posting another
version. The patch itself looks good to me:

Acked-by: Nikolay Aleksandrov <razor@blackwall.org>