Re: [PATCH 5.10 018/145] net: dcb: Validate netlink message in DCB handler

[Jakub Kicinski]

On Mon, 11 Jan 2021 14:00:42 +0100 Greg Kroah-Hartman wrote:
> From: Petr Machata <me@xxxxxxxxxxxx>
> 
> [ Upstream commit 826f328e2b7e8854dd42ea44e6519cd75018e7b1 ]
> 
> DCB uses the same handler function for both RTM_GETDCB and RTM_SETDCB
> messages. dcb_doit() bounces RTM_SETDCB mesasges if the user does not have
> the CAP_NET_ADMIN capability.
> 
> However, the operation to be performed is not decided from the DCB message
> type, but from the DCB command. Thus DCB_CMD_*_GET commands are used for
> reading DCB objects, the corresponding SET and DEL commands are used for
> manipulation.
> 
> The assumption is that set-like commands will be sent via an RTM_SETDCB
> message, and get-like ones via RTM_GETDCB. However, this assumption is not
> enforced.
> 
> It is therefore possible to manipulate DCB objects without CAP_NET_ADMIN
> capability by sending the corresponding command in an RTM_GETDCB message.
> That is a bug. Fix it by validating the type of the request message against
> the type used for the response.
> 
> Fixes: 2f90b8657ec9 ("ixgbe: this patch adds support for DCB to the kernel and ixgbe driver")
> Signed-off-by: Petr Machata <me@xxxxxxxxxxxx>
> Link: https://lore.kernel.org/r/a2a9b88418f3a58ef211b718f2970128ef9e3793.1608673640.git.me@xxxxxxxxxxxx
> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

Unfortunately we need to call backsies on this one.

A fix up was just posted:

https://patchwork.kernel.org/project/netdevbpf/patch/a3edcfda0825f2aa2591801c5232f2bbf2d8a554.1610384801.git.me@xxxxxxxxxxxx/

I'll resend both in the next submission.