[PATCH V4 1/4] xen: Make struct privcmd_irqfd's layout architecture independent

[Viresh Kumar]

Using indirect pointers in an ioctl command argument means that the
layout is architecture specific, in particular we can't use the same one
from 32-bit compat tasks. The general recommendation is to have __u64
members and use u64_to_user_ptr() to access it from the kernel if we are
unable to avoid the pointers altogether.

Fixes: f8941e6c4c71 ("xen: privcmd: Add support for irqfd")
Reported-by: Arnd Bergmann <arnd@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/268a2031-63b8-4c7d-b1e5-8ab83ca80b4a@xxxxxxxxxxxxxxxx/
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
 drivers/xen/privcmd.c      | 2 +-
 include/uapi/xen/privcmd.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 120af57999fc..5095bd1abea5 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -935,7 +935,7 @@ static int privcmd_irqfd_assign(struct privcmd_irqfd *irqfd)
 		return -ENOMEM;
 	dm_op = kirqfd + 1;
 
-	if (copy_from_user(dm_op, irqfd->dm_op, irqfd->size)) {
+	if (copy_from_user(dm_op, u64_to_user_ptr(irqfd->dm_op), irqfd->size)) {
 		ret = -EFAULT;
 		goto error_kfree;
 	}
diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h
index 375718ba4ab6..b143fafce84d 100644
--- a/include/uapi/xen/privcmd.h
+++ b/include/uapi/xen/privcmd.h
@@ -102,7 +102,7 @@ struct privcmd_mmap_resource {
 #define PRIVCMD_IRQFD_FLAG_DEASSIGN (1 << 0)
 
 struct privcmd_irqfd {
-	void __user *dm_op;
+	__u64 dm_op;
 	__u32 size; /* Size of structure pointed by dm_op */
 	__u32 fd;
 	__u32 flags;
-- 
2.31.1.272.g89b43f80a514