drivers/md/md-bitmap: check the return value of md_bitmap_get_counter()

[ Upstream commit 3bd548e5b819b8c0f2c9085de775c5c7bff9052f ]

Check the return value of md_bitmap_get_counter() in case it returns
NULL pointer, which will result in a null pointer dereference.

v2: update the check to include other dereference

Signed-off-by: Li Zhong <floridsleeves@gmail.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index 8cc11b1..650bfcc 100644 (file)
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -2196,20 +2196,23 @@ int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks,
 
                if (set) {
                        bmc_new = md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1);
-                       if (*bmc_new == 0) {
-                               /* need to set on-disk bits too. */
-                               sector_t end = block + new_blocks;
-                               sector_t start = block >> chunkshift;
-                               start <<= chunkshift;
-                               while (start < end) {
-                                       md_bitmap_file_set_bit(bitmap, block);
-                                       start += 1 << chunkshift;
+                       if (bmc_new) {
+                               if (*bmc_new == 0) {
+                                       /* need to set on-disk bits too. */
+                                       sector_t end = block + new_blocks;
+                                       sector_t start = block >> chunkshift;
+
+                                       start <<= chunkshift;
+                                       while (start < end) {
+                                               md_bitmap_file_set_bit(bitmap, block);
+                                               start += 1 << chunkshift;
+                                       }
+                                       *bmc_new = 2;
+                                       md_bitmap_count_page(&bitmap->counts, block, 1);
+                                       md_bitmap_set_pending(&bitmap->counts, block);
                                }
-                               *bmc_new = 2;
-                               md_bitmap_count_page(&bitmap->counts, block, 1);
-                               md_bitmap_set_pending(&bitmap->counts, block);
+                               *bmc_new |= NEEDED_MASK;
                        }
-                       *bmc_new |= NEEDED_MASK;
                        if (new_blocks < old_blocks)
                                old_blocks = new_blocks;
                }