exfat: check return value of sb_min_blocksize in exfat_read_boot_sector

sb_min_blocksize() may return 0. Check its return value to avoid
accessing the filesystem super block when sb->s_blocksize is 0.

Cc: stable@vger.kernel.org # v6.15
Fixes: 719c1e1 ("exfat: add super block operations")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Yongpeng Yang <yangyongpeng@xiaomi.com>
Link: https://patch.msgid.link/20251104125009.2111925-3-yangyongpeng.storage@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Yongpeng Yang

fs/exfat/super.c

@@ -433,7 +433,10 @@ static int exfat_read_boot_sector(struct super_block *sb)
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 
 	/* set block size to read super block */
-	sb_min_blocksize(sb, 512);
+	if (!sb_min_blocksize(sb, 512)) {
+		exfat_err(sb, "unable to set blocksize");
+		return -EINVAL;
+	}
 
 	/* read boot sector */
 	sbi->boot_bh = sb_bread(sb, 0);