[PATCH 2/2] ext2: Avoid rec_len overflow with 64KB block size

Mingming Cao
2007-10-02T00:50:31Z

ext2: Avoid rec_len overflow with 64KB block size

From: Jan Kara <jack@suse.cz>

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

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
---

fs/ext2/dir.c | 43 +++++++++++++++++++++++++++++++------------
include/linux/ext2_fs.h | 1 +
2 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index 2bf49d7..1329bdb 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -26,6 +26,24 @@

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
@@ -95,7 +113,7 @@ 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;
@@ -193,7 +211,8 @@ 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
@@ -305,7 +324,7 @@ 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);
}
@@ -413,7 +432,7 @@ void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
struct page *page, struct inode *inode)
{
unsigned from = (char *) de - (char *) page_address(page);
- unsigned to = from + le16_to_cpu(de->rec_len);
+ unsigned to = from + ext2_rec_len_from_disk(de->rec_len);
int err;

lock_page(page);
@@ -469,7 +488,7 @@ 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;
}
@@ -483,7 +502,7 @@ 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)
@@ -504,8 +523,8 @@ 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;
@@ -536,7 +555,7 @@ 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);
ext2_dirent * pde = NULL;
ext2_dirent * de = (ext2_dirent *) (kaddr + from);
int err;
@@ -557,7 +576,7 @@ int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
err = mapping->a_ops->prepare_write(NULL, page, from, to);
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, from, to);
inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
@@ -591,14 +610,14 @@ 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 910a705..41063d5 100644
--- a/include/linux/ext2_fs.h
+++ b/include/linux/ext2_fs.h
@@ -557,5 +557,6 @@ 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)

#endif /* _LINUX_EXT2_FS_H */