resize.f2fs: fix to avoid zeroing main area blocks in migrate_ssa()

The `new_seg_total` may be greater than the total number of blocks
in the SSA, which can cause main area blocks to be zeroed out during
SSA migration. This can corrupt the root inode, leading to filesystem
corruption.

Fixes: ad1357c ("f2fs-tools: revert summary entry count from 2048 to 512 in 16kb block support")
Signed-off-by: Yangyang Zang <zangyangyang1@xiaomi.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: zangyangyang666

fsck/resize.c

@@ -257,48 +257,48 @@ static void migrate_ssa(struct f2fs_sb_info *sbi,
 	struct f2fs_super_block *sb = F2FS_RAW_SUPER(sbi);
 	block_t old_sum_blkaddr = get_sb(ssa_blkaddr);
 	block_t new_sum_blkaddr = get_newsb(ssa_blkaddr);
-	unsigned int expand_segno = MAIN_SEGS(sbi) - offset;
-	unsigned int new_seg_total = get_newsb(segment_count);
-	int new_segno;
+	unsigned int expand_sum_blocks = MAIN_SEGS(sbi) - offset;
+	unsigned int new_sum_blocks = get_newsb(main_blkaddr) - new_sum_blkaddr;
+	int new_sum_blkoff;
 	int ret = 0;
 	void *zero_block = calloc(F2FS_SUM_BLKSIZE, 1);
 	ASSERT(zero_block);
 
 	if (offset && new_sum_blkaddr <= (old_sum_blkaddr +
 				offset / SUMS_PER_BLOCK)) {
-		new_segno = 0;
-		while (new_segno < new_seg_total) {
-			if (new_segno < expand_segno)
-				move_ssa(sbi, new_sb, offset++, new_segno);
+		new_sum_blkoff = 0;
+		while (new_sum_blkoff < new_sum_blocks) {
+			if (new_sum_blkoff < expand_sum_blocks)
+				move_ssa(sbi, new_sb, offset++, new_sum_blkoff);
 			else if (c.feature & F2FS_FEATURE_PACKED_SSA)
 				ret = dev_write_4k_block(zero_block,
-					GET_SUM_NEW_BLKADDR(new_sb, new_segno),
-					GET_SUM_NEW_BLKOFF(new_sb, new_segno),
+					GET_SUM_NEW_BLKADDR(new_sb, new_sum_blkoff),
+					GET_SUM_NEW_BLKOFF(new_sb, new_sum_blkoff),
 					WRITE_LIFE_NONE);
 			else
 				ret = dev_write_block(zero_block,
-					GET_SUM_NEW_BLKADDR(new_sb, new_segno),
+					GET_SUM_NEW_BLKADDR(new_sb, new_sum_blkoff),
 					WRITE_LIFE_NONE);
 			ASSERT(ret >= 0);
-			new_segno++;
+			new_sum_blkoff++;
 		}
 	} else {
-		new_segno = new_seg_total - 1;
+		new_sum_blkoff = new_sum_blocks - 1;
 		offset = MAIN_SEGS(sbi) - 1;
-		while (new_segno >= 0) {
-			if (new_segno < expand_segno)
-				move_ssa(sbi, new_sb, offset--, new_segno);
+		while (new_sum_blkoff >= 0) {
+			if (new_sum_blkoff < expand_sum_blocks)
+				move_ssa(sbi, new_sb, offset--, new_sum_blkoff);
 			else if (c.feature & F2FS_FEATURE_PACKED_SSA)
 				ret = dev_write_4k_block(zero_block,
-					GET_SUM_NEW_BLKADDR(new_sb, new_segno),
-					GET_SUM_NEW_BLKOFF(new_sb, new_segno),
+					GET_SUM_NEW_BLKADDR(new_sb, new_sum_blkoff),
+					GET_SUM_NEW_BLKOFF(new_sb, new_sum_blkoff),
 					WRITE_LIFE_NONE);
 			else
 				ret = dev_write_block(zero_block,
-					GET_SUM_NEW_BLKADDR(new_sb, new_segno),
+					GET_SUM_NEW_BLKADDR(new_sb, new_sum_blkoff),
 					WRITE_LIFE_NONE);
 			ASSERT(ret >= 0);
-			new_segno--;
+			new_sum_blkoff--;
 		}
 	}