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SubjectRe: [PATCH net-next 1/2 v3] uevent: add alloc_uevent_skb() helper
On Fri, Apr 27, 2018 at 11:39:44AM -0500, Eric W. Biederman wrote:
> Christian Brauner <christian.brauner@ubuntu.com> writes:
>
> > This patch adds alloc_uevent_skb() in preparation for follow up patches.
> >
> > Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
> > ---
> > lib/kobject_uevent.c | 39 ++++++++++++++++++++++++++-------------
> > 1 file changed, 26 insertions(+), 13 deletions(-)
> >
> > diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> > index 15ea216a67ce..c3cb110f663b 100644
> > --- a/lib/kobject_uevent.c
> > +++ b/lib/kobject_uevent.c
> > @@ -296,6 +296,31 @@ static void cleanup_uevent_env(struct subprocess_info *info)
> > }
> > #endif
> >
> > +static struct sk_buff *alloc_uevent_skb(struct kobj_uevent_env *env,
> > + const char *action_string,
> > + const char *devpath)
> > +{
> > + struct sk_buff *skb = NULL;
> > + char *scratch;
> > + size_t len;
> > +
> > + /* allocate message with maximum possible size */
> > + len = strlen(action_string) + strlen(devpath) + 2;
> > + skb = alloc_skb(len + env->buflen, GFP_KERNEL);
> > + if (!skb)
> > + return NULL;
> > +
> > + /* add header */
> > + scratch = skb_put(skb, len);
> > + sprintf(scratch, "%s@%s", action_string, devpath);
> > +
> > + skb_put_data(skb, env->buf, env->buflen);
> > +
> > + NETLINK_CB(skb).dst_group = 1;
>
> nit:
> We might want to explicitly set NETLINK_CB(skb).portid to 0 and
> NETLINK_CB(skb).creds.uid to GLOBAL_ROOT_UID and
> NETLINK_CB(skb).creds.gid to GLOBAL_ROOT_GID here
> just to make it clear this is happening.
>
> It is not a problem because they __alloc_skb memsets to 0 the
> fields of struct sk_buff that it does not initialize. And these
> are the zero values.
>
> Still it would be nice to be able to look at the code and quickly
> see these are the values being set.

Don't really mind adding it. Ok, non-functional changes added to the new
version. But then let's set "portid" too:

parms = &NETLINK_CB(skb);
parms->creds.uid = GLOBAL_ROOT_UID;
parms->creds.gid = GLOBAL_ROOT_GID;
parms->dst_group = 1;
parms->portid = 0;

Christian

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