Re: [PATCH net v2] rtnetlink: fix error logic of IFLA_BRIDGE_FLAGS writing back

[Nikolay Aleksandrov]

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@xxxxxxxxxx>
> ---
> 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@xxxxxxxxxxxxx>