udf: Fortify loading of sparing table

commit 1df2ae31c724e57be9d7ac00d78db8a5dabdd050 upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 800e839..270e135 100644 (file)
--- 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"
@@ -1217,11 +1218,59 @@ 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;
@@ -1283,38 +1332,9 @@ 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))) {