| From 882f908778da7570332f89b0e64a8905924440fe Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Sun, 30 Aug 2026 10:33:54 +0800 |
| Subject: vduse: validate virtqueue alignment |
| |
| From: Jia Jia <physicalmtea@gmail.com> |
| |
| [ Upstream commit fa2c25b4add57888acfa89e398389e267bff3dcf ] |
| |
| vduse_validate_config() only checks the upper bound of vq_align. Invalid |
| values can therefore reach vring_create_virtqueue_map(). The split-ring |
| helpers use align - 1 as a bit mask, so the alignment must be a non-zero |
| power of two. A zero value makes vring_size() drop the descriptor and |
| available-ring part and vring_init() leave the used ring pointer NULL. |
| |
| The VIRTIO spec requires the used ring to start at an address |
| aligned to at least 4 bytes. Reject values below VRING_USED_ALIGN_SIZE as |
| well as non-power-of-two values before they reach the virtio ring helpers. |
| |
| Opening a virtio-net device created with vq_align=0 triggered: |
| |
| BUG: KASAN: null-ptr-deref in virtqueue_kick_prepare_split+0xe3/0x100 |
| Read of size 2 at addr 0000000000000000 by task systemd-network/1062 |
| |
| Call Trace (relevant frames): |
| dump_stack_lvl |
| print_report |
| kasan_report |
| __asan_load2 |
| virtqueue_kick_prepare_split+0xe3/0x100 |
| virtqueue_kick_prepare+0x40/0x60 |
| try_fill_recv+0x857/0x1250 |
| virtnet_open+0x189/0x460 |
| __dev_open+0x225/0x390 |
| __dev_change_flags+0x368/0x3b0 |
| netif_change_flags+0x56/0xc0 |
| do_setlink.isra.0+0x68c/0x1e30 |
| |
| Validate the value before it reaches the virtio ring helpers. |
| |
| Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace") |
| Signed-off-by: Jia Jia <physicalmtea@gmail.com> |
| Signed-off-by: Michael S. Tsirkin <mst@redhat.com> |
| Message-ID: <20260830023354.115333-1-physicalmtea@gmail.com> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| drivers/vdpa/vdpa_user/vduse_dev.c | 4 +++- |
| 1 file changed, 3 insertions(+), 1 deletion(-) |
| |
| diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c |
| index 1cc826742ac9c..f9547ede71be7 100644 |
| --- a/drivers/vdpa/vdpa_user/vduse_dev.c |
| +++ b/drivers/vdpa/vdpa_user/vduse_dev.c |
| @@ -1837,7 +1837,9 @@ static bool vduse_validate_config(struct vduse_dev_config *config) |
| sizeof(config->reserved))) |
| return false; |
| |
| - if (config->vq_align > PAGE_SIZE) |
| + if (config->vq_align < VRING_USED_ALIGN_SIZE || |
| + !is_power_of_2(config->vq_align) || |
| + config->vq_align > PAGE_SIZE) |
| return false; |
| |
| if (config->config_size > PAGE_SIZE) |
| -- |
| 2.53.0 |
| |
