[PATCH 2/2] powerpc/vas: Return -EINVAL if the offset is non-zero in mmap()

[Madhavan Srinivasan]

The user space calls mmap() to map VAS window paste address
and the kernel returns the complete mapped page for each
window. So return -EINVAL if non-zero is passed for offset
parameter to mmap().

See Documentation/arch/powerpc/vas-api.rst for mmap()
restrictions.

Co-developed-by: Jonathan Greental <yonatan02green...@gmail.com>
Signed-off-by: Jonathan Greental <yonatan02green...@gmail.com>
Reported-by: Jonathan Greental <yonatan02green...@gmail.com>
Fixes: dda44eb29c23 ("powerpc/vas: Add VAS user space API")
Signed-off-by: Haren Myneni <ha...@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <ma...@linux.ibm.com>
---
 arch/powerpc/platforms/book3s/vas-api.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/platforms/book3s/vas-api.c 
b/arch/powerpc/platforms/book3s/vas-api.c
index 0b6365d85d11..dc6f75d3ac6e 100644
--- a/arch/powerpc/platforms/book3s/vas-api.c
+++ b/arch/powerpc/platforms/book3s/vas-api.c
@@ -521,6 +521,15 @@ static int coproc_mmap(struct file *fp, struct 
vm_area_struct *vma)
                return -EINVAL;
        }
 
+       /*
+        * Map complete page to the paste address. So the user
+        * space should pass 0ULL to the offset parameter.
+        */
+       if (vma->vm_pgoff) {
+               pr_debug("Page offset unsupported to map paste address\n");
+               return -EINVAL;
+       }
+
        /* Ensure instance has an open send window */
        if (!txwin) {
                pr_err("No send window open?\n");
-- 
2.46.0