mm: Fix devm_memremap_pages() collision handling

commit 77dd66a3 upstream.

If devm_memremap_pages() detects a collision while adding entries
to the radix-tree, we call pgmap_radix_release(). Unfortunately,
the function removes *all* entries for the range -- including the
entries that caused the collision in the first place.

Modify pgmap_radix_release() to take an additional argument to
indicate where to stop, so that only newly added entries are removed
from the tree.

Cc: <stable@vger.kernel.org>
Fixes: 9476df7d ("mm: introduce find_dev_pagemap()")
Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kernel/memremap.c

@@ -194,7 +194,7 @@ void put_zone_device_page(struct page *page)
 }
 EXPORT_SYMBOL(put_zone_device_page);
 
-static void pgmap_radix_release(struct resource *res)
+static void pgmap_radix_release(struct resource *res, resource_size_t end_key)
 {
 	resource_size_t key, align_start, align_size, align_end;
 
@@ -203,8 +203,11 @@ static void pgmap_radix_release(struct resource *res)
 	align_end = align_start + align_size - 1;
 
 	mutex_lock(&pgmap_lock);
-	for (key = res->start; key <= res->end; key += SECTION_SIZE)
+	for (key = res->start; key <= res->end; key += SECTION_SIZE) {
+		if (key >= end_key)
+			break;
 		radix_tree_delete(&pgmap_radix, key >> PA_SECTION_SHIFT);
+	}
 	mutex_unlock(&pgmap_lock);
 }
 
@@ -255,7 +258,7 @@ static void devm_memremap_pages_release(struct device *dev, void *data)
 	unlock_device_hotplug();
 
 	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
-	pgmap_radix_release(res);
+	pgmap_radix_release(res, -1);
 	dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc,
 			"%s: failed to free all reserved pages\n", __func__);
 }
@@ -289,7 +292,7 @@ struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
 void *devm_memremap_pages(struct device *dev, struct resource *res,
 		struct percpu_ref *ref, struct vmem_altmap *altmap)
 {
-	resource_size_t key, align_start, align_size, align_end;
+	resource_size_t key = 0, align_start, align_size, align_end;
 	pgprot_t pgprot = PAGE_KERNEL;
 	struct dev_pagemap *pgmap;
 	struct page_map *page_map;
@@ -392,7 +395,7 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
 	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
  err_pfn_remap:
  err_radix:
-	pgmap_radix_release(res);
+	pgmap_radix_release(res, key);
 	devres_free(page_map);
 	return ERR_PTR(error);
 }