[bug report] mm/gup: remove vmas parameter from get_user_pages_remote()

[Dan Carpenter <dan.carpenter@linaro.org>]

Hello Lorenzo Stoakes,

The patch eca1a00155df: "mm/gup: remove vmas parameter from
get_user_pages_remote()" from May 14, 2023, leads to the following
Smatch static checker warning:

	mm/memory.c:5617 __access_remote_vm()
	error: uninitialized symbol 'vma'.

mm/memory.c
    5590 int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
    5591                        int len, unsigned int gup_flags)
    5592 {
    5593         void *old_buf = buf;
    5594         int write = gup_flags & FOLL_WRITE;
    5595 
    5596         if (mmap_read_lock_killable(mm))
    5597                 return 0;
    5598 
    5599         /* ignore errors, just check how much was successfully transferred */
    5600         while (len) {
    5601                 int bytes, offset;
    5602                 void *maddr;
    5603                 struct vm_area_struct *vma;
    5604                 struct page *page = get_user_page_vma_remote(mm, addr,
    5605                                                              gup_flags, &vma);
    5606 
    5607                 if (IS_ERR_OR_NULL(page)) {

If page is either an error pointer or NULL then

    5608                         int ret = 0;
    5609 
    5610 #ifndef CONFIG_HAVE_IOREMAP_PROT
    5611                         break;
    5612 #else
    5613                         /*
    5614                          * Check if this is a VM_IO | VM_PFNMAP VMA, which
    5615                          * we can access using slightly different code.
    5616                          */
--> 5617                         if (!vma)

that means vma is unitialized.

    5618                                 break;
    5619                         if (vma->vm_ops && vma->vm_ops->access)
    5620                                 ret = vma->vm_ops->access(vma, addr, buf,
    5621                                                           len, write);
    5622                         if (ret <= 0)
    5623                                 break;
    5624                         bytes = ret;
    5625 #endif
    5626                 } else {
    5627                         bytes = len;
    5628                         offset = addr & (PAGE_SIZE-1);
    5629                         if (bytes > PAGE_SIZE-offset)
    5630                                 bytes = PAGE_SIZE-offset;
    5631 
    5632                         maddr = kmap(page);
    5633                         if (write) {
    5634                                 copy_to_user_page(vma, page, addr,
    5635                                                   maddr + offset, buf, bytes);
    5636                                 set_page_dirty_lock(page);
    5637                         } else {
    5638                                 copy_from_user_page(vma, page, addr,
    5639                                                     buf, maddr + offset, bytes);
    5640                         }
    5641                         kunmap(page);
    5642                         put_page(page);
    5643                 }
    5644                 len -= bytes;
    5645                 buf += bytes;
    5646                 addr += bytes;
    5647         }
    5648         mmap_read_unlock(mm);
    5649 
    5650         return buf - old_buf;
    5651 }

regards,
dan carpenter