[PATCH 2/2] vduse: fix compat handling for VDUSE_IOTLB_GET_FD/VDUSE_VQ_GET_INFO

[Arnd Bergmann <arnd@kernel.org>]

From: Arnd Bergmann <arnd@arndb.de>

These two ioctls are incompatible on 32-bit x86 userspace, because
the data structures are shorter than they are on 64-bit.

Add compad handling to the regular ioctl handler to just handle
them the same way and ignore the extra padding. This could be
done in a separate .compat_ioctl handler, but the main one already
handles two versions of VDUSE_IOTLB_GET_FD, so adding a third one
fits in rather well.

Fixes: ad146355bfad ("vduse: Support querying information of IOVA regions")
Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/vdpa/vdpa_user/vduse_dev.c | 43 +++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index 405d59610f76..39cbff2f379d 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -1341,6 +1341,37 @@ static int vduse_dev_iotlb_entry(struct vduse_dev *dev,
 	return r;
 }
 
+#if defined(CONFIG_X86_64) && defined(CONFIG_COMPAT)
+/*
+ * i386 has different alignment constraints than x86_64,
+ * so there are only 3 bytes of padding instead of 7.
+ */
+struct compat_vduse_iotlb_entry {
+	compat_u64 offset;
+	compat_u64 start;
+	compat_u64 last;
+	__u8 perm;
+	__u8 padding[__alignof__(compat_u64) - 1];
+};
+#define COMPAT_VDUSE_IOTLB_GET_FD	_IOWR(VDUSE_BASE, 0x10, struct compat_vduse_iotlb_entry)
+
+struct compat_vduse_vq_info {
+	__u32 index;
+	__u32 num;
+	compat_u64 desc_addr;
+	compat_u64 driver_addr;
+	compat_u64 device_addr;
+	union {
+		struct vduse_vq_state_split split;
+		struct vduse_vq_state_packed packed;
+	};
+	__u8 ready;
+	__u8 padding[__alignof__(compat_u64) - 1];
+} __uapi_arch_align;
+#define COMPAT_VDUSE_VQ_GET_INFO	_IOWR(VDUSE_BASE, 0x15, struct compat_vduse_vq_info)
+
+#endif
+
 static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
 			    unsigned long arg)
 {
@@ -1352,6 +1383,9 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
 		return -EPERM;
 
 	switch (cmd) {
+#if defined(CONFIG_X86_64) && defined(CONFIG_COMPAT)
+	case COMPAT_VDUSE_IOTLB_GET_FD:
+#endif
 	case VDUSE_IOTLB_GET_FD:
 	case VDUSE_IOTLB_GET_FD2: {
 		struct vduse_iotlb_entry_v2 entry = {0};
@@ -1455,13 +1489,16 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
 		ret = 0;
 		break;
 	}
+#if defined(CONFIG_X86_64) && defined(CONFIG_COMPAT)
+	case COMPAT_VDUSE_VQ_GET_INFO:
+#endif
 	case VDUSE_VQ_GET_INFO: {
-		struct vduse_vq_info vq_info;
+		struct vduse_vq_info vq_info = {};
 		struct vduse_virtqueue *vq;
 		u32 index;
 
 		ret = -EFAULT;
-		if (copy_from_user(&vq_info, argp, sizeof(vq_info)))
+		if (copy_from_user(&vq_info, argp, _IOC_SIZE(cmd)))
 			break;
 
 		ret = -EINVAL;
@@ -1491,7 +1528,7 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
 		vq_info.ready = vq->ready;
 
 		ret = -EFAULT;
-		if (copy_to_user(argp, &vq_info, sizeof(vq_info)))
+		if (copy_to_user(argp, &vq_info, _IOC_SIZE(cmd)))
 			break;
 
 		ret = 0;
-- 
2.39.5