xen/netback: don't call kfree_skb() with interrupts disabled

xen/netback: don't call kfree_skb() with interrupts disabled

Origin: https://git.kernel.org/linus/74e7e1efdad45580cc3839f2a155174cf158f9b5
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2022-42329
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2022-42328

It is not allowed to call kfree_skb() from hardware interrupt
context or with interrupts being disabled. So remove kfree_skb()
from the spin_lock_irqsave() section and use the already existing
"drop" label in xenvif_start_xmit() for dropping the SKB. At the
same time replace the dev_kfree_skb() call there with a call of
dev_kfree_skb_any(), as xenvif_start_xmit() can be called with
disabled interrupts.

This is XSA-424 / CVE-2022-42328 / CVE-2022-42329.

Fixes: be81992f9086 ("xen/netback: don't queue unlimited number of packages")
Reported-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Gbp-Pq: Topic bugfix/all
Gbp-Pq: Name xen-netback-don-t-call-kfree_skb-with-interrupts-dis.patch