[PATCH OLK-5.10 v3 1/4] md/raid10: fix slab-out-of-bounds in md_bitmap_get_counter

[linan666]

From: Li Nan <linan122@xxxxxxxxxx>

If we write a large number to md/bitmap_set_bits, md_bitmap_checkpage()
will return -EINVAL because 'page >= bitmap->pages', but the return value
was not checked immediately in md_bitmap_get_counter() in order to set
*blocks value and slab-out-of-bounds occurs.

Move check of 'page >= bitmap->pages' to md_bitmap_get_counter() and
return directly if true.

Fixes: ef4256733506 ("md/bitmap: optimise scanning of empty bitmaps.")
Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 drivers/md/md-bitmap.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index 920bb68156d2..e122b19c124d 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -46,6 +46,7 @@ static inline char *bmname(struct bitmap *bitmap)
  *
  * if we find our page, we increment the page's refcount so that it stays
  * allocated while we're using it
+ * the caller must make sure 'page < bimap->pages'
  */
 static int md_bitmap_checkpage(struct bitmap_counts *bitmap,
 			       unsigned long page, int create, int no_hijack)
@@ -54,14 +55,6 @@ __acquires(bitmap->lock)
 {
 	unsigned char *mappage;
 
-	if (page >= bitmap->pages) {
-		/* This can happen if bitmap_start_sync goes beyond
-		 * End-of-device while looking for a whole page.
-		 * It is harmless.
-		 */
-		return -EINVAL;
-	}
-
 	if (bitmap->bp[page].hijacked) /* it's hijacked, don't try to alloc */
 		return 0;
 
@@ -1387,6 +1380,14 @@ __acquires(bitmap->lock)
 	sector_t csize;
 	int err;
 
+	if (page >= bitmap->pages) {
+		/*
+		 * This can happen if bitmap_start_sync goes beyond
+		 * End-of-device while looking for a whole page or
+		 * user set a huge number to sysfs bitmap_set_bits.
+		 */
+		return NULL;
+	}
 	err = md_bitmap_checkpage(bitmap, page, create, 0);
 
 	if (bitmap->bp[page].hijacked ||
-- 
2.31.1