linux-kernel - Re: [PATCH net v2] rtnetlink: fix error logic of IFLA_BRIDGE

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Date: Tue, 27 Feb 2024 14:48:59 +0200
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Lin Ma <linma@....edu.cn>, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, idosch@...dia.com, jiri@...nulli.us,
 lucien.xin@...il.com, edwin.peer@...adcom.com, amcohen@...dia.com,
 pctammela@...atatu.com, liuhangbin@...il.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2] rtnetlink: fix error logic of IFLA_BRIDGE_FLAGS
 writing back

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@....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@...ckwall.org>