Re: [PATCH net] xfrm_user: fix info leak in build_mapping()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Apr 06, 2026 at 10:38:51AM -0700, Jakub Kicinski wrote:
> On Mon, 6 Apr 2026 18:08:27 +0200 Greg Kroah-Hartman wrote:
> > On Mon, Apr 06, 2026 at 08:58:59AM -0700, Jakub Kicinski wrote:
> > > On Mon, 6 Apr 2026 08:54:49 -0700 Jakub Kicinski wrote:  
> > > > You're right, skb owner is responsible for clearing after put.
> > > > Tho, Netlink is not as perf critical as real networking, I wish
> > > > we at least had a helper which reserves the space and clears it :/
> > > > This is not the first or the second time we hit this sort of a bug.  
> > > 
> > > We could make nlmsg_append() do that. Mostly because I don't have 
> > > a better idea for a name and nlmsg_append is only used once ;)  
> > 
> > As shown in my other patch:
> > 	https://lore.kernel.org/r/2026040621-poison-gristle-aaa3@gregkh
> > we need this in at least 2 places, don't know if it's worth doing it for
> > all messages?
> 
> I was thinking -- add the helper so that we can use it in places we're
> touching anyway. No need to mess with correct existing code.
> 
> > I guess nlmsg_append() would work?  It tries to do some zeroing out for
> > alignment for some reason...
> > 
> > Want me to do that?  I don't have a way to test any of this, I just
> > found it using some static code analysis tools that looked at holes in
> > structures.
> 
> Do you have any more Netlink leaks in the queue? If you do let's do it,
> if you don't we can wait until the next victi^w patch to arrive.

I do not have any more, sorry.  So is it worth it for just these 2?
Your call :)