ext2: avoid rec_len overflow with 64KB block size

With 64KB blocksize, a directory entry can have size 64KB which does not
fit into 16 bits we have for entry length.  So we store 0xffff instead and
convert the value when read from / written to disk.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 33 insertions, 12 deletions

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index 05d9342bb64e..d868e26c15eb 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -28,6 +28,24 @@
 
 typedef struct ext2_dir_entry_2 ext2_dirent;
 
+static inline unsigned ext2_rec_len_from_disk(__le16 dlen)
+{
+        unsigned len = le16_to_cpu(dlen);
+
+        if (len == EXT2_MAX_REC_LEN)
+                return 1 << 16;
+        return len;
+}
+
+static inline __le16 ext2_rec_len_to_disk(unsigned len)
+{
+        if (len == (1 << 16))
+                return cpu_to_le16(EXT2_MAX_REC_LEN);
+        else if (len > (1 << 16))
+                BUG();
+        return cpu_to_le16(len);
+}
+
 /*
  * ext2 uses block-sized chunks. Arguably, sector-sized ones would be
  * more robust, but we have what we have
@@ -106,7 +124,7 @@ static void ext2_check_page(struct page *page)
         }
         for (offs = 0; offs <= limit - EXT2_DIR_REC_LEN(1); offs += rec_len) {
                 p = (ext2_dirent *)(kaddr + offs);
-                rec_len = le16_to_cpu(p->rec_len);
+                rec_len = ext2_rec_len_from_disk(p->rec_len);
 
                 if (rec_len < EXT2_DIR_REC_LEN(1))
                         goto Eshort;
@@ -204,7 +222,8 @@ static inline int ext2_match (int len, const char * const name,
  */
 static inline ext2_dirent *ext2_next_entry(ext2_dirent *p)
 {
-        return (ext2_dirent *)((char*)p + le16_to_cpu(p->rec_len));
+        return (ext2_dirent *)((char *)p +
+                        ext2_rec_len_from_disk(p->rec_len));
 }
 
 static inline unsigned 
@@ -316,7 +335,7 @@ ext2_readdir (struct file * filp, void * dirent, filldir_t filldir)
                                         return 0;
                                 }
                         }
-                        filp->f_pos += le16_to_cpu(de->rec_len);
+                        filp->f_pos += ext2_rec_len_from_disk(de->rec_len);
                 }
                 ext2_put_page(page);
         }
@@ -425,7 +444,7 @@ void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
 {
         loff_t pos = page_offset(page) +
                         (char *) de - (char *) page_address(page);
-        unsigned len = le16_to_cpu(de->rec_len);
+        unsigned len = ext2_rec_len_from_disk(de->rec_len);
         int err;
 
         lock_page(page);
@@ -482,7 +501,7 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
                                 /* We hit i_size */
                                 name_len = 0;
                                 rec_len = chunk_size;
-                                de->rec_len = cpu_to_le16(chunk_size);
+                                de->rec_len = ext2_rec_len_to_disk(chunk_size);
                                 de->inode = 0;
                                 goto got_it;
                         }
@@ -496,7 +515,7 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
                         if (ext2_match (namelen, name, de))
                                 goto out_unlock;
                         name_len = EXT2_DIR_REC_LEN(de->name_len);
-                        rec_len = le16_to_cpu(de->rec_len);
+                        rec_len = ext2_rec_len_from_disk(de->rec_len);
                         if (!de->inode && rec_len >= reclen)
                                 goto got_it;
                         if (rec_len >= name_len + reclen)
@@ -518,8 +537,8 @@ got_it:
                 goto out_unlock;
         if (de->inode) {
                 ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
-                de1->rec_len = cpu_to_le16(rec_len - name_len);
-                de->rec_len = cpu_to_le16(name_len);
+                de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
+                de->rec_len = ext2_rec_len_to_disk(name_len);
                 de = de1;
         }
         de->name_len = namelen;
@@ -550,7 +569,8 @@ int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
         struct inode *inode = mapping->host;
         char *kaddr = page_address(page);
         unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);
-        unsigned to = ((char*)dir - kaddr) + le16_to_cpu(dir->rec_len);
+        unsigned to = ((char *)dir - kaddr) +
+                                ext2_rec_len_from_disk(dir->rec_len);
         loff_t pos;
         ext2_dirent * pde = NULL;
         ext2_dirent * de = (ext2_dirent *) (kaddr + from);
@@ -574,7 +594,7 @@ int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
                                                         &page, NULL);
         BUG_ON(err);
         if (pde)
-                pde->rec_len = cpu_to_le16(to - from);
+                pde->rec_len = ext2_rec_len_to_disk(to - from);
         dir->inode = 0;
         err = ext2_commit_chunk(page, pos, to - from);
         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
@@ -610,14 +630,14 @@ int ext2_make_empty(struct inode *inode, struct inode *parent)
         memset(kaddr, 0, chunk_size);
         de = (struct ext2_dir_entry_2 *)kaddr;
         de->name_len = 1;
-        de->rec_len = cpu_to_le16(EXT2_DIR_REC_LEN(1));
+        de->rec_len = ext2_rec_len_to_disk(EXT2_DIR_REC_LEN(1));
         memcpy (de->name, ".\0\0", 4);
         de->inode = cpu_to_le32(inode->i_ino);
         ext2_set_de_type (de, inode);
 
         de = (struct ext2_dir_entry_2 *)(kaddr + EXT2_DIR_REC_LEN(1));
         de->name_len = 2;
-        de->rec_len = cpu_to_le16(chunk_size - EXT2_DIR_REC_LEN(1));
+        de->rec_len = ext2_rec_len_to_disk(chunk_size - EXT2_DIR_REC_LEN(1));
         de->inode = cpu_to_le32(parent->i_ino);
         memcpy (de->name, "..\0", 4);
         ext2_set_de_type (de, inode);
diff --git a/include/linux/ext2_fs.h b/include/linux/ext2_fs.h
index c77c3bbfe4bb..0f6c86c634fd 100644
--- a/include/linux/ext2_fs.h
+++ b/include/linux/ext2_fs.h
@@ -561,6 +561,7 @@ enum {
 #define EXT2_DIR_ROUND                  (EXT2_DIR_PAD - 1)
 #define EXT2_DIR_REC_LEN(name_len)      (((name_len) + 8 + EXT2_DIR_ROUND) & \
                                          ~EXT2_DIR_ROUND)
+#define EXT2_MAX_REC_LEN                ((1<<16)-1)
 
 static inline ext2_fsblk_t
 ext2_group_first_block_no(struct super_block *sb, unsigned long group_no)