Staging: TIDSPBRIDGE: Fix mmap to map the correct region of physical memory

Commit 559c71fe5dc3 ("Staging: TIDSPBRIDGE: Use vm_iomap_memory for
mmap-ing instead of remap_pfn_range") had the effect of inadvertently
shifting the start of the physical memory area mapped by
pdata->phys_mempool_base.  Correct this by subtracting that shift before
calling vm_iomap_memory() and adding it back afterwards.

Reported-by: Dheeraj CVR <cvr.dheeraj@gmail.com>
Signed-off-by: Ivaylo Dimitrov <freemangordon@abv.bg>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/tidspbridge/rmgr/drv_interface.c b/drivers/staging/tidspbridge/rmgr/drv_interface.c
index 56e355b..fec5afc 100644 (file)
--- a/drivers/staging/tidspbridge/rmgr/drv_interface.c
+++ b/drivers/staging/tidspbridge/rmgr/drv_interface.c
@@ -258,6 +258,8 @@ err:
 /* This function maps kernel space memory to user space memory. */
 static int bridge_mmap(struct file *filp, struct vm_area_struct *vma)
 {
+       unsigned long base_pgoff;
+       int status;
        struct omap_dsp_platform_data *pdata =
                                        omap_dspbridge_dev->dev.platform_data;
 
@@ -269,9 +271,31 @@ static int bridge_mmap(struct file *filp, struct vm_area_struct *vma)
                vma->vm_start, vma->vm_end, vma->vm_page_prot,
                vma->vm_flags);
 
-       return vm_iomap_memory(vma,
-                              pdata->phys_mempool_base,
-                              pdata->phys_mempool_size);
+       /*
+        * vm_iomap_memory() expects vma->vm_pgoff to be expressed as an offset
+        * from the start of the physical memory pool, but we're called with
+        * a pfn (physical page number) stored there instead.
+        *
+        * To avoid duplicating lots of tricky overflow checking logic,
+        * temporarily convert vma->vm_pgoff to the offset vm_iomap_memory()
+        * expects, but restore the original value once the mapping has been
+        * created.
+        */
+       base_pgoff = pdata->phys_mempool_base >> PAGE_SHIFT;
+
+       if (vma->vm_pgoff < base_pgoff)
+               return -EINVAL;
+
+       vma->vm_pgoff -= base_pgoff;
+
+       status = vm_iomap_memory(vma,
+                                pdata->phys_mempool_base,
+                                pdata->phys_mempool_size);
+
+       /* Restore the original value of vma->vm_pgoff */
+       vma->vm_pgoff += base_pgoff;
+
+       return status;
 }
 
 static const struct file_operations bridge_fops = {