fs/ntfs3: validate BOOT sectors_per_clusters

When the NTFS BOOT sectors_per_clusters field is > 0x80, it represents a
shift value.  Make sure that the shift value is not too large before using
it (NTFS max cluster size is 2MB).  Return -EVINVAL if it too large.

This prevents negative shift values and shift values that are larger than
the field size.

Prevents this UBSAN error:

 UBSAN: shift-out-of-bounds in ../fs/ntfs3/super.c:673:16
 shift exponent -192 is negative

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 82cae26 ("fs/ntfs3: Add initialization of super block")
Signed-off-by: Randy Dunlap <[email protected]>
Reported-by: [email protected]
Reviewed-by: Namjae Jeon <[email protected]>
Cc: Konstantin Komarov <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Kari Argillander <[email protected]>
Cc: Namjae Jeon <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

fs/ntfs3/super.c

@@ -668,9 +668,11 @@ static u32 format_size_gb(const u64 bytes, u32 *mb)
 
 static u32 true_sectors_per_clst(const struct NTFS_BOOT *boot)
 {
-	return boot->sectors_per_clusters <= 0x80
-		       ? boot->sectors_per_clusters
-		       : (1u << (0 - boot->sectors_per_clusters));
+	if (boot->sectors_per_clusters <= 0x80)
+		return boot->sectors_per_clusters;
+	if (boot->sectors_per_clusters >= 0xf4) /* limit shift to 2MB max */
+		return 1U << (0 - boot->sectors_per_clusters);
+	return -EINVAL;
 }
 
 /*
@@ -713,6 +715,8 @@ static int ntfs_init_from_boot(struct super_block *sb, u32 sector_size,
 
 	/* cluster size: 512, 1K, 2K, 4K, ... 2M */
 	sct_per_clst = true_sectors_per_clst(boot);
+	if ((int)sct_per_clst < 0)
+		goto out;
 	if (!is_power_of_2(sct_per_clst))
 		goto out;