isofs: Fix unbounded recursion when processing relocated directories

We did not check relocated directory in any way when processing Rock
Ridge 'CL' tag. Thus a corrupted isofs image can possibly have a CL
entry pointing to another CL entry leading to possibly unbounded
recursion in kernel code and thus stack overflow or deadlocks (if there
is a loop created from CL entries).

Fix the problem by not allowing CL entry to point to a directory entry
with CL entry (such use makes no good sense anyway) and by checking
whether CL entry doesn't point to itself.

CC: stable@vger.kernel.org
Reported-by: Chris Evans <cevans@google.com>
Signed-off-by: Jan Kara <jack@suse.cz>

3 files changed, 55 insertions, 22 deletions

diff --git a/fs/isofs/inode.c b/fs/isofs/inode.c
index 4556ce1af5b0..5ddaf8625d3b 100644
--- a/fs/isofs/inode.c
+++ b/fs/isofs/inode.c
@@ -61,7 +61,7 @@ static void isofs_put_super(struct super_block *sb)
         return;
 }
 
-static int isofs_read_inode(struct inode *);
+static int isofs_read_inode(struct inode *, int relocated);
 static int isofs_statfs (struct dentry *, struct kstatfs *);
 
 static struct kmem_cache *isofs_inode_cachep;
@@ -1259,7 +1259,7 @@ out_toomany:
         goto out;
 }
 
-static int isofs_read_inode(struct inode *inode)
+static int isofs_read_inode(struct inode *inode, int relocated)
 {
         struct super_block *sb = inode->i_sb;
         struct isofs_sb_info *sbi = ISOFS_SB(sb);
@@ -1404,7 +1404,7 @@ static int isofs_read_inode(struct inode *inode)
          */
 
         if (!high_sierra) {
-                parse_rock_ridge_inode(de, inode);
+                parse_rock_ridge_inode(de, inode, relocated);
                 /* if we want uid/gid set, override the rock ridge setting */
                 if (sbi->s_uid_set)
                         inode->i_uid = sbi->s_uid;
@@ -1483,9 +1483,10 @@ static int isofs_iget5_set(struct inode *ino, void *data)
  * offset that point to the underlying meta-data for the inode.  The
  * code below is otherwise similar to the iget() code in
  * include/linux/fs.h */
-struct inode *isofs_iget(struct super_block *sb,
-                         unsigned long block,
-                         unsigned long offset)
+struct inode *__isofs_iget(struct super_block *sb,
+                           unsigned long block,
+                           unsigned long offset,
+                           int relocated)
 {
         unsigned long hashval;
         struct inode *inode;
@@ -1507,7 +1508,7 @@ struct inode *isofs_iget(struct super_block *sb,
                 return ERR_PTR(-ENOMEM);
 
         if (inode->i_state & I_NEW) {
-                ret = isofs_read_inode(inode);
+                ret = isofs_read_inode(inode, relocated);
                 if (ret < 0) {
                         iget_failed(inode);
                         inode = ERR_PTR(ret);
diff --git a/fs/isofs/isofs.h b/fs/isofs/isofs.h
index 99167238518d..0ac4c1f73fbd 100644
--- a/fs/isofs/isofs.h
+++ b/fs/isofs/isofs.h
@@ -107,7 +107,7 @@ extern int iso_date(char *, int);
 
 struct inode;           /* To make gcc happy */
 
-extern int parse_rock_ridge_inode(struct iso_directory_record *, struct inode *);
+extern int parse_rock_ridge_inode(struct iso_directory_record *, struct inode *, int relocated);
 extern int get_rock_ridge_filename(struct iso_directory_record *, char *, struct inode *);
 extern int isofs_name_translate(struct iso_directory_record *, char *, struct inode *);
 
@@ -118,9 +118,24 @@ extern struct dentry *isofs_lookup(struct inode *, struct dentry *, unsigned int
 extern struct buffer_head *isofs_bread(struct inode *, sector_t);
 extern int isofs_get_blocks(struct inode *, sector_t, struct buffer_head **, unsigned long);
 
-extern struct inode *isofs_iget(struct super_block *sb,
-                                unsigned long block,
-                                unsigned long offset);
+struct inode *__isofs_iget(struct super_block *sb,
+                           unsigned long block,
+                           unsigned long offset,
+                           int relocated);
+
+static inline struct inode *isofs_iget(struct super_block *sb,
+                                       unsigned long block,
+                                       unsigned long offset)
+{
+        return __isofs_iget(sb, block, offset, 0);
+}
+
+static inline struct inode *isofs_iget_reloc(struct super_block *sb,
+                                             unsigned long block,
+                                             unsigned long offset)
+{
+        return __isofs_iget(sb, block, offset, 1);
+}
 
 /* Because the inode number is no longer relevant to finding the
  * underlying meta-data for an inode, we are free to choose a more
diff --git a/fs/isofs/rock.c b/fs/isofs/rock.c
index c0bf42472e40..f488bbae541a 100644
--- a/fs/isofs/rock.c
+++ b/fs/isofs/rock.c
@@ -288,12 +288,16 @@ eio:
         goto out;
 }
 
+#define RR_REGARD_XA 1
+#define RR_RELOC_DE 2
+
 static int
 parse_rock_ridge_inode_internal(struct iso_directory_record *de,
-                                struct inode *inode, int regard_xa)
+                                struct inode *inode, int flags)
 {
         int symlink_len = 0;
         int cnt, sig;
+        unsigned int reloc_block;
         struct inode *reloc;
         struct rock_ridge *rr;
         int rootflag;
@@ -305,7 +309,7 @@ parse_rock_ridge_inode_internal(struct iso_directory_record *de,
 
         init_rock_state(&rs, inode);
         setup_rock_ridge(de, inode, &rs);
-        if (regard_xa) {
+        if (flags & RR_REGARD_XA) {
                 rs.chr += 14;
                 rs.len -= 14;
                 if (rs.len < 0)
@@ -485,12 +489,22 @@ repeat:
                                         "relocated directory\n");
                         goto out;
                 case SIG('C', 'L'):
-                        ISOFS_I(inode)->i_first_extent =
-                            isonum_733(rr->u.CL.location);
-                        reloc =
-                            isofs_iget(inode->i_sb,
-                                       ISOFS_I(inode)->i_first_extent,
-                                       0);
+                        if (flags & RR_RELOC_DE) {
+                                printk(KERN_ERR
+                                       "ISOFS: Recursive directory relocation "
+                                       "is not supported\n");
+                                goto eio;
+                        }
+                        reloc_block = isonum_733(rr->u.CL.location);
+                        if (reloc_block == ISOFS_I(inode)->i_iget5_block &&
+                            ISOFS_I(inode)->i_iget5_offset == 0) {
+                                printk(KERN_ERR
+                                       "ISOFS: Directory relocation points to "
+                                       "itself\n");
+                                goto eio;
+                        }
+                        ISOFS_I(inode)->i_first_extent = reloc_block;
+                        reloc = isofs_iget_reloc(inode->i_sb, reloc_block, 0);
                         if (IS_ERR(reloc)) {
                                 ret = PTR_ERR(reloc);
                                 goto out;
@@ -637,9 +651,11 @@ static char *get_symlink_chunk(char *rpnt, struct rock_ridge *rr, char *plimit)
         return rpnt;
 }
 
-int parse_rock_ridge_inode(struct iso_directory_record *de, struct inode *inode)
+int parse_rock_ridge_inode(struct iso_directory_record *de, struct inode *inode,
+                           int relocated)
 {
-        int result = parse_rock_ridge_inode_internal(de, inode, 0);
+        int flags = relocated ? RR_RELOC_DE : 0;
+        int result = parse_rock_ridge_inode_internal(de, inode, flags);
 
         /*
          * if rockridge flag was reset and we didn't look for attributes
@@ -647,7 +663,8 @@ int parse_rock_ridge_inode(struct iso_directory_record *de, struct inode *inode)
          */
         if ((ISOFS_SB(inode->i_sb)->s_rock_offset == -1)
             && (ISOFS_SB(inode->i_sb)->s_rock == 2)) {
-                result = parse_rock_ridge_inode_internal(de, inode, 14);
+                result = parse_rock_ridge_inode_internal(de, inode,
+                                                         flags | RR_REGARD_XA);
         }
         return result;
 }