udf: limit the maximum number of TD redirections
Filesystem fuzzing revealed that we could get stuck in the
udf_process_sequence() loop.
The maximum limit was chosen arbitrarily but fixes the problem I saw.
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/udf/super.c b/fs/udf/super.c
index 81155b9..fd45537 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -1586,6 +1586,13 @@
}
/*
+ * Maximum number of Terminating Descriptor redirections. The chosen number is
+ * arbitrary - just that we hopefully don't limit any real use of rewritten
+ * inode on write-once media but avoid looping for too long on corrupted media.
+ */
+#define UDF_MAX_TD_NESTING 64
+
+/*
* Process a main/reserve volume descriptor sequence.
* @block First block of first extent of the sequence.
* @lastblock Lastblock of first extent of the sequence.
@@ -1609,6 +1616,7 @@
uint16_t ident;
long next_s = 0, next_e = 0;
int ret;
+ unsigned int indirections = 0;
memset(vds, 0, sizeof(struct udf_vds_record) * VDS_POS_LENGTH);
@@ -1679,6 +1687,12 @@
}
break;
case TAG_IDENT_TD: /* ISO 13346 3/10.9 */
+ if (++indirections > UDF_MAX_TD_NESTING) {
+ udf_err(sb, "too many TDs (max %u supported)\n", UDF_MAX_TD_NESTING);
+ brelse(bh);
+ return -EIO;
+ }
+
vds[VDS_POS_TERMINATING_DESC].block = block;
if (next_e) {
block = next_s;