[PATCH 5.10 015/509] md/raid10: check slab-out-of-bounds in md_bitmap_get_counter

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From: Li Nan <linan122@xxxxxxxxxx>

[ Upstream commit 301867b1c16805aebbc306aafa6ecdc68b73c7e5 ]

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>
Signed-off-by: Song Liu <song@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230515134808.3936750-2-linan666@xxxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@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 20afc0aec1778..f843ade442dec 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -54,14 +54,7 @@ __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;
-	}
-
+	WARN_ON_ONCE(page >= bitmap->pages);
 	if (bitmap->bp[page].hijacked) /* it's hijacked, don't try to alloc */
 		return 0;
 
@@ -1365,6 +1358,14 @@ __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 ||
-- 
2.39.2






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