udf: Fortify loading of sparing table

Add sanity checks when loading sparing table from disk to avoid accessing
unallocated memory or writing to it.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 53 insertions, 33 deletions

diff --git a/fs/udf/super.c b/fs/udf/super.c
index ce911f50b39d..8d86a8706c0e 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -56,6 +56,7 @@
 #include <linux/seq_file.h>
 #include <linux/bitmap.h>
 #include <linux/crc-itu-t.h>
+#include <linux/log2.h>
 #include <asm/byteorder.h>
 
 #include "udf_sb.h"
@@ -1215,11 +1216,59 @@ out_bh:
         return ret;
 }
 
+static int udf_load_sparable_map(struct super_block *sb,
+                                 struct udf_part_map *map,
+                                 struct sparablePartitionMap *spm)
+{
+        uint32_t loc;
+        uint16_t ident;
+        struct sparingTable *st;
+        struct udf_sparing_data *sdata = &map->s_type_specific.s_sparing;
+        int i;
+        struct buffer_head *bh;
+
+        map->s_partition_type = UDF_SPARABLE_MAP15;
+        sdata->s_packet_len = le16_to_cpu(spm->packetLength);
+        if (!is_power_of_2(sdata->s_packet_len)) {
+                udf_err(sb, "error loading logical volume descriptor: "
+                        "Invalid packet length %u\n",
+                        (unsigned)sdata->s_packet_len);
+                return -EIO;
+        }
+        if (spm->numSparingTables > 4) {
+                udf_err(sb, "error loading logical volume descriptor: "
+                        "Too many sparing tables (%d)\n",
+                        (int)spm->numSparingTables);
+                return -EIO;
+        }
+
+        for (i = 0; i < spm->numSparingTables; i++) {
+                loc = le32_to_cpu(spm->locSparingTable[i]);
+                bh = udf_read_tagged(sb, loc, loc, &ident);
+                if (!bh)
+                        continue;
+
+                st = (struct sparingTable *)bh->b_data;
+                if (ident != 0 ||
+                    strncmp(st->sparingIdent.ident, UDF_ID_SPARING,
+                            strlen(UDF_ID_SPARING)) ||
+                    sizeof(*st) + le16_to_cpu(st->reallocationTableLen) >
+                                                        sb->s_blocksize) {
+                        brelse(bh);
+                        continue;
+                }
+
+                sdata->s_spar_map[i] = bh;
+        }
+        map->s_partition_func = udf_get_pblock_spar15;
+        return 0;
+}
+
 static int udf_load_logicalvol(struct super_block *sb, sector_t block,
                                struct kernel_lb_addr *fileset)
 {
         struct logicalVolDesc *lvd;
-        int i, j, offset;
+        int i, offset;
         uint8_t type;
         struct udf_sb_info *sbi = UDF_SB(sb);
         struct genericPartitionMap *gpm;
@@ -1281,38 +1330,9 @@ static int udf_load_logicalvol(struct super_block *sb, sector_t block,
                         } else if (!strncmp(upm2->partIdent.ident,
                                                 UDF_ID_SPARABLE,
                                                 strlen(UDF_ID_SPARABLE))) {
-                                uint32_t loc;
-                                struct sparingTable *st;
-                                struct sparablePartitionMap *spm =
-                                        (struct sparablePartitionMap *)gpm;
-
-                                map->s_partition_type = UDF_SPARABLE_MAP15;
-                                map->s_type_specific.s_sparing.s_packet_len =
-                                                le16_to_cpu(spm->packetLength);
-                                for (j = 0; j < spm->numSparingTables; j++) {
-                                        struct buffer_head *bh2;
-
-                                        loc = le32_to_cpu(
-                                                spm->locSparingTable[j]);
-                                        bh2 = udf_read_tagged(sb, loc, loc,
-                                                             &ident);
-                                        map->s_type_specific.s_sparing.
-                                                        s_spar_map[j] = bh2;
-
-                                        if (bh2 == NULL)
-                                                continue;
-
-                                        st = (struct sparingTable *)bh2->b_data;
-                                        if (ident != 0 || strncmp(
-                                                st->sparingIdent.ident,
-                                                UDF_ID_SPARING,
-                                                strlen(UDF_ID_SPARING))) {
-                                                brelse(bh2);
-                                                map->s_type_specific.s_sparing.
-                                                        s_spar_map[j] = NULL;
-                                        }
-                                }
-                                map->s_partition_func = udf_get_pblock_spar15;
+                                if (udf_load_sparable_map(sb, map,
+                                    (struct sparablePartitionMap *)gpm) < 0)
+                                        goto out_bh;
                         } else if (!strncmp(upm2->partIdent.ident,
                                                 UDF_ID_METADATA,
                                                 strlen(UDF_ID_METADATA))) {