virtio_net: Fix napi_skb_cache_put warning

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: virtio_net: Fix napi_skb_cache_put warning After the commit bdacf3e34945 ("net: Use nested-BH locking for napi_alloc_cache.") was merged, the following warning began to appear: WARNING: CPU: 5 PID: 1 at net/core/skbuff.c:1451 napi_skb_cache_put+0x82/0x4b0 __warn+0x12f/0x340 napi_skb_cache_put+0x82/0x4b0 napi_skb_cache_put+0x82/0x4b0 report_bug+0x165/0x370 handle_bug+0x3d/0x80 exc_invalid_op+0x1a/0x50 asm_exc_invalid_op+0x1a/0x20 __free_old_xmit+0x1c8/0x510 napi_skb_cache_put+0x82/0x4b0 __free_old_xmit+0x1c8/0x510 __free_old_xmit+0x1c8/0x510 __pfx___free_old_xmit+0x10/0x10 The issue arises because virtio is assuming it's running in NAPI context even when it's not, such as in the netpoll case. To resolve this, modify virtnet_poll_tx() to only set NAPI when budget is available. Same for virtnet_poll_cleantx(), which always assumed that it was in a NAPI context.

References

• https://git.kernel.org/stable/c/d3af435e8ace119e58d8e21d3d2d6a4e7c4a4baa
• https://git.kernel.org/stable/c/842a97b5e44f0c8a9fc356fe976e0e13ddcf7783
• https://git.kernel.org/stable/c/cc7340f18e45886121c131227985d64ef666012f
• https://git.kernel.org/stable/c/6b5325f2457521bbece29499970c0117a648c620
• https://git.kernel.org/stable/c/f5e9a22d19bb98a7e86034db85eb295e94187caa
• https://git.kernel.org/stable/c/468a729b78895893d0e580ceea49bed8ada2a2bd
• https://git.kernel.org/stable/c/f8321fa75102246d7415a6af441872f6637c93ab