[PATCH net v2] virtio-net: free xsk_buffs on error in virtnet_xsk_pool_enable()

[Jakub Kicinski <kuba@kernel.org>]

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

Acked-by: Jason Wang <jasowang@redhat.com>
Fixes: e9f3962441c0 ("virtio_net: xsk: rx: support fill with xsk buffer")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
v2:
 - remember to set the err
v1: https://lore.kernel.org/20250429164323.2637891-1-kuba@kernel.org

CC: mst@redhat.com
CC: jasowang@redhat.com
CC: xuanzhuo@linux.alibaba.com
CC: eperezma@redhat.com
CC: hawk@kernel.org
CC: john.fastabend@gmail.com
CC: virtualization@lists.linux.dev
CC: minhquangbui99@gmail.com
---
 drivers/net/virtio_net.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 848fab51dfa1..c107916b685e 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -5885,8 +5885,10 @@ static int virtnet_xsk_pool_enable(struct net_device *dev,
 
 	hdr_dma = virtqueue_dma_map_single_attrs(sq->vq, &xsk_hdr, vi->hdr_len,
 						 DMA_TO_DEVICE, 0);
-	if (virtqueue_dma_mapping_error(sq->vq, hdr_dma))
-		return -ENOMEM;
+	if (virtqueue_dma_mapping_error(sq->vq, hdr_dma)) {
+		err = -ENOMEM;
+		goto err_free_buffs;
+	}
 
 	err = xsk_pool_dma_map(pool, dma_dev, 0);
 	if (err)
@@ -5914,6 +5916,8 @@ static int virtnet_xsk_pool_enable(struct net_device *dev,
 err_xsk_map:
 	virtqueue_dma_unmap_single_attrs(rq->vq, hdr_dma, vi->hdr_len,
 					 DMA_TO_DEVICE, 0);
+err_free_buffs:
+	kvfree(rq->xsk_buffs);
 	return err;
 }
 
-- 
2.49.0