udf: Check LVID earlier

We were checking validity of LVID entries only when getting
implementation use information from LVID in udf_sb_lvidiu(). However if
the LVID is suitably corrupted, it can cause problems also to code such
as udf_count_free() which doesn't use udf_sb_lvidiu(). So check validity
of LVID already when loading it from the disk and just disable LVID
altogether when it is not valid.

Reported-by: syzbot+7fbfe5fed73ebb675748@syzkaller.appspotmail.com
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/super.c

@@ -108,16 +108,10 @@ struct logicalVolIntegrityDescImpUse *udf_sb_lvidiu(struct super_block *sb)
 		return NULL;
 	lvid = (struct logicalVolIntegrityDesc *)UDF_SB(sb)->s_lvid_bh->b_data;
 	partnum = le32_to_cpu(lvid->numOfPartitions);
-	if ((sb->s_blocksize - sizeof(struct logicalVolIntegrityDescImpUse) -
-	     offsetof(struct logicalVolIntegrityDesc, impUse)) /
-	     (2 * sizeof(uint32_t)) < partnum) {
-		udf_err(sb, "Logical volume integrity descriptor corrupted "
-			"(numOfPartitions = %u)!\n", partnum);
-		return NULL;
-	}
 	/* The offset is to skip freeSpaceTable and sizeTable arrays */
 	offset = partnum * 2 * sizeof(uint32_t);
-	return (struct logicalVolIntegrityDescImpUse *)&(lvid->impUse[offset]);
+	return (struct logicalVolIntegrityDescImpUse *)
+					(((uint8_t *)(lvid + 1)) + offset);
 }
 
 /* UDF filesystem type */
@@ -1542,6 +1536,7 @@ static void udf_load_logicalvolint(struct super_block *sb, struct kernel_extent_
 	struct udf_sb_info *sbi = UDF_SB(sb);
 	struct logicalVolIntegrityDesc *lvid;
 	int indirections = 0;
+	u32 parts, impuselen;
 
 	while (++indirections <= UDF_MAX_LVID_NESTING) {
 		final_bh = NULL;
@@ -1568,15 +1563,27 @@ static void udf_load_logicalvolint(struct super_block *sb, struct kernel_extent_
 
 		lvid = (struct logicalVolIntegrityDesc *)final_bh->b_data;
 		if (lvid->nextIntegrityExt.extLength == 0)
-			return;
+			goto check;
 
 		loc = leea_to_cpu(lvid->nextIntegrityExt);
 	}
 
 	udf_warn(sb, "Too many LVID indirections (max %u), ignoring.\n",
 		UDF_MAX_LVID_NESTING);
+out_err:
 	brelse(sbi->s_lvid_bh);
 	sbi->s_lvid_bh = NULL;
+	return;
+check:
+	parts = le32_to_cpu(lvid->numOfPartitions);
+	impuselen = le32_to_cpu(lvid->lengthOfImpUse);
+	if (parts >= sb->s_blocksize || impuselen >= sb->s_blocksize ||
+	    sizeof(struct logicalVolIntegrityDesc) + impuselen +
+	    2 * parts * sizeof(u32) > sb->s_blocksize) {
+		udf_warn(sb, "Corrupted LVID (parts=%u, impuselen=%u), "
+			 "ignoring.\n", parts, impuselen);
+		goto out_err;
+	}
 }
 
 /*