CVE-2014-6410: Resource Management Errors (CWE-399)
value: The __udf_read_inode function in fs/udf/inode.c in the Linux kernel through 3.16.3 does not restrict the amount of ICB indirection, which allows physically proximate attackers to cause a denial of service (infinite loop or stack consumption) via a UDF filesystem with a crafted inode.
CWE description: Weaknesses in this category are related to improper management of system resources.
Published: 2014-09-28T10:55Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: fs/udf/inode.c
Commit date: 2014-09-04 14:12:29 +0200
Commit message: udf: Avoid infinite loop when processing indirect ICBs

We did not implement any bound on number of indirect ICBs we follow when
loading inode. Thus corrupted medium could cause kernel to go into an
infinite loop, possibly causing a stack overflow.

Fix the possible stack overflow by removing recursion from
__udf_read_inode() and limit number of indirect ICBs we follow to avoid
infinite loops.

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

Diff: diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 68cc7b144c260b..a6a40536ebf139 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1268,20 +1268,29 @@ int udf_setsize(struct inode *inode, loff_t newsize)
 	else
 		mark_inode_dirty(inode);
 	return 0;
 }
 
+/*
+ * Maximum length of linked list formed by ICB hierarchy. 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_ICB_NESTING 1024
+
 static void __udf_read_inode(struct inode *inode)
 {
 	struct buffer_head *bh = NULL;
 	struct fileEntry *fe;
 	struct extendedFileEntry *efe;
 	uint16_t ident;
 	struct udf_inode_info *iinfo = UDF_I(inode);
 	struct udf_sb_info *sbi = UDF_SB(inode->i_sb);
 	unsigned int link_count;
+	unsigned int indirections = 0;
 
+reread:
 	/*
 	 * Set defaults, but the inode is still incomplete!
 	 * Note: get_new_inode() sets the following on a new inode:
 	 *      i_sb = sb
 	 *      i_no = ino
@@ -1315,32 +1324,30 @@ static void __udf_read_inode(struct inode *inode)
 		struct buffer_head *ibh;
 
 		ibh = udf_read_ptagged(inode->i_sb, &iinfo->i_location, 1,
 					&ident);
 		if (ident == TAG_IDENT_IE && ibh) {
-			struct buffer_head *nbh = NULL;
 			struct kernel_lb_addr loc;
 			struct indirectEntry *ie;
 
 			ie = (struct indirectEntry *)ibh->b_data;
 			loc = lelb_to_cpu(ie->indirectICB.extLocation);
 
-			if (ie->indirectICB.extLength &&
-				(nbh = udf_read_ptagged(inode->i_sb, &loc, 0,
-							&ident))) {
-				if (ident == TAG_IDENT_FE ||
-					ident == TAG_IDENT_EFE) {
-					memcpy(&iinfo->i_location,
-						&loc,
-						sizeof(struct kernel_lb_addr));
-					brelse(bh);
-					brelse(ibh);
-					brelse(nbh);
-					__udf_read_inode(inode);
+			if (ie->indirectICB.extLength) {
+				brelse(bh);
+				brelse(ibh);
+				memcpy(&iinfo->i_location, &loc,
+				       sizeof(struct kernel_lb_addr));
+				if (++indirections > UDF_MAX_ICB_NESTING) {
+					udf_err(inode->i_sb,
+						"too many ICBs in ICB hierarchy"
+						" (max %d supported)\n",
+						UDF_MAX_ICB_NESTING);
+					make_bad_inode(inode);
 					return;
 				}
-				brelse(nbh);
+				goto reread;
 			}
 		}
 		brelse(ibh);
 	} else if (fe->icbTag.strategyType != cpu_to_le16(4)) {
 		udf_err(inode->i_sb, "unsupported strategy type: %d\n",

Vulnerable code: 			struct buffer_head *nbh = NULL;
			if (ie->indirectICB.extLength &&
				(nbh = udf_read_ptagged(inode->i_sb, &loc, 0,
							&ident))) {
				if (ident == TAG_IDENT_FE ||
					ident == TAG_IDENT_EFE) {
					memcpy(&iinfo->i_location,
						&loc,
						sizeof(struct kernel_lb_addr));
					brelse(bh);
					brelse(ibh);
					brelse(nbh);
					__udf_read_inode(inode);
				brelse(nbh);
Fixed code: /*
 * Maximum length of linked list formed by ICB hierarchy. 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_ICB_NESTING 1024

	unsigned int indirections = 0;
reread:
			if (ie->indirectICB.extLength) {
				brelse(bh);
				brelse(ibh);
				memcpy(&iinfo->i_location, &loc,
				       sizeof(struct kernel_lb_addr));
				if (++indirections > UDF_MAX_ICB_NESTING) {
					udf_err(inode->i_sb,
						"too many ICBs in ICB hierarchy"
						" (max %d supported)\n",
						UDF_MAX_ICB_NESTING);
					make_bad_inode(inode);
				goto reread;