virtio-net: free xsk_buffs on error in virtnet_xsk_pool_enable()

In the Linux kernel, the following vulnerability has been resolved:

virtio-net: free xsk_buffs on error in virtnet_xsk_pool_enable()

The selftests added to our CI by Bui Quang Minh recently reveals

that there is a mem leak on the error path of virtnet_xsk_pool_enable():

unreferenced object 0xffff88800a68a000 (size 2048):

comm "xdp_helper", pid 318, jiffies 4294692778

hex dump (first 32 bytes):

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

backtrace (crc 0):

__kvmalloc_node_noprof+0x402/0x570

virtnet_xsk_pool_enable+0x293/0x6a0 (drivers/net/virtio_net.c:5882)

xp_assign_dev+0x369/0x670 (net/xdp/xsk_buff_pool.c:226)

xsk_bind+0x6a5/0x1ae0

__sys_bind+0x15e/0x230

__x64_sys_bind+0x72/0xb0

do_syscall_64+0xc1/0x1d0

entry_SYSCALL_64_after_hwframe+0x77/0x7f