[PATCH 2/2] ext4: Avoid rec_len overflow with 64KB block size

From: Mingming Cao
Date: Mon Oct 01 2007 - 20:41:49 EST

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ext4: Avoid rec_len overflow with 64KB block size

From: Jan Kara <jack@xxxxxxx>

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. The patch also converts some places
to use ext4_next_entry() when we are changing them anyway.

Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Mingming Cao <cmm@xxxxxxxxxx>
---

fs/ext4/dir.c | 12 ++++---
fs/ext4/namei.c | 76 ++++++++++++++++++++++-------------------------
include/linux/ext4_fs.h | 20 ++++++++++++
3 files changed, 62 insertions(+), 46 deletions(-)

diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 3ab01c0..20b1e28 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -69,7 +69,7 @@ int ext4_check_dir_entry (const char * function, struct inode * dir,
unsigned long offset)
{
const char * error_msg = NULL;
- const int rlen = le16_to_cpu(de->rec_len);
+ const int rlen = ext4_rec_len_from_disk(de->rec_len);

if (rlen < EXT4_DIR_REC_LEN(1))
error_msg = "rec_len is smaller than minimal";
@@ -176,10 +176,10 @@ revalidate:
* least that it is non-zero. A
* failure will be detected in the
* dirent test below. */
- if (le16_to_cpu(de->rec_len) <
- EXT4_DIR_REC_LEN(1))
+ if (ext4_rec_len_from_disk(de->rec_len)
+ < EXT4_DIR_REC_LEN(1))
break;
- i += le16_to_cpu(de->rec_len);
+ i += ext4_rec_len_from_disk(de->rec_len);
}
offset = i;
filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
@@ -201,7 +201,7 @@ revalidate:
ret = stored;
goto out;
}
- offset += le16_to_cpu(de->rec_len);
+ offset += ext4_rec_len_from_disk(de->rec_len);
if (le32_to_cpu(de->inode)) {
/* We might block in the next section
* if the data destination is
@@ -223,7 +223,7 @@ revalidate:
goto revalidate;
stored ++;
}
- filp->f_pos += le16_to_cpu(de->rec_len);
+ filp->f_pos += ext4_rec_len_from_disk(de->rec_len);
}
offset = 0;
brelse (bh);
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 5fdb862..96e8a85 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -281,7 +281,7 @@ static struct stats dx_show_leaf(struct dx_hash_info *hinfo, struct ext4_dir_ent
space += EXT4_DIR_REC_LEN(de->name_len);
names++;
}
- de = (struct ext4_dir_entry_2 *) ((char *) de + le16_to_cpu(de->rec_len));
+ de = ext4_next_entry(de);
}
printk("(%i)\n", names);
return (struct stats) { names, space, 1 };
@@ -552,7 +552,8 @@ static int ext4_htree_next_block(struct inode *dir, __u32 hash,
*/
static inline struct ext4_dir_entry_2 *ext4_next_entry(struct ext4_dir_entry_2 *p)
{
- return (struct ext4_dir_entry_2 *)((char*)p + le16_to_cpu(p->rec_len));
+ return (struct ext4_dir_entry_2 *)((char*)p +
+ ext4_rec_len_from_disk(p->rec_len));
}

/*
@@ -721,7 +722,7 @@ static int dx_make_map (struct ext4_dir_entry_2 *de, int size,
cond_resched();
}
/* XXX: do we need to check rec_len == 0 case? -Chris */
- de = (struct ext4_dir_entry_2 *) ((char *) de + le16_to_cpu(de->rec_len));
+ de = ext4_next_entry(de);
}
return count;
}
@@ -823,7 +824,7 @@ static inline int search_dirblock(struct buffer_head * bh,
return 1;
}
/* prevent looping on a bad block */
- de_len = le16_to_cpu(de->rec_len);
+ de_len = ext4_rec_len_from_disk(de->rec_len);
if (de_len <= 0)
return -1;
offset += de_len;
@@ -1136,7 +1137,7 @@ dx_move_dirents(char *from, char *to, struct dx_map_entry *map, int count)
rec_len = EXT4_DIR_REC_LEN(de->name_len);
memcpy (to, de, rec_len);
((struct ext4_dir_entry_2 *) to)->rec_len =
- cpu_to_le16(rec_len);
+ ext4_rec_len_to_disk(rec_len);
de->inode = 0;
map++;
to += rec_len;
@@ -1155,13 +1156,12 @@ static struct ext4_dir_entry_2* dx_pack_dirents(char *base, int size)

prev = to = de;
while ((char*)de < base + size) {
- next = (struct ext4_dir_entry_2 *) ((char *) de +
- le16_to_cpu(de->rec_len));
+ next = ext4_next_entry(de);
if (de->inode && de->name_len) {
rec_len = EXT4_DIR_REC_LEN(de->name_len);
if (de > to)
memmove(to, de, rec_len);
- to->rec_len = cpu_to_le16(rec_len);
+ to->rec_len = ext4_rec_len_to_disk(rec_len);
prev = to;
to = (struct ext4_dir_entry_2 *) (((char *) to) + rec_len);
}
@@ -1235,8 +1235,8 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
/* Fancy dance to stay within two buffers */
de2 = dx_move_dirents(data1, data2, map + split, count - split);
de = dx_pack_dirents(data1,blocksize);
- de->rec_len = cpu_to_le16(data1 + blocksize - (char *) de);
- de2->rec_len = cpu_to_le16(data2 + blocksize - (char *) de2);
+ de->rec_len = ext4_rec_len_to_disk(data1 + blocksize - (char *) de);
+ de2->rec_len = ext4_rec_len_to_disk(data2 + blocksize - (char *) de2);
dxtrace(dx_show_leaf (hinfo, (struct ext4_dir_entry_2 *) data1, blocksize, 1));
dxtrace(dx_show_leaf (hinfo, (struct ext4_dir_entry_2 *) data2, blocksize, 1));

@@ -1307,7 +1307,7 @@ static int add_dirent_to_buf(handle_t *handle, struct dentry *dentry,
return -EEXIST;
}
nlen = EXT4_DIR_REC_LEN(de->name_len);
- rlen = le16_to_cpu(de->rec_len);
+ rlen = ext4_rec_len_from_disk(de->rec_len);
if ((de->inode? rlen - nlen: rlen) >= reclen)
break;
de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
@@ -1326,11 +1326,11 @@ static int add_dirent_to_buf(handle_t *handle, struct dentry *dentry,

/* By now the buffer is marked for journaling */
nlen = EXT4_DIR_REC_LEN(de->name_len);
- rlen = le16_to_cpu(de->rec_len);
+ rlen = ext4_rec_len_from_disk(de->rec_len);
if (de->inode) {
struct ext4_dir_entry_2 *de1 = (struct ext4_dir_entry_2 *)((char *)de + nlen);
- de1->rec_len = cpu_to_le16(rlen - nlen);
- de->rec_len = cpu_to_le16(nlen);
+ de1->rec_len = ext4_rec_len_to_disk(rlen - nlen);
+ de->rec_len = ext4_rec_len_to_disk(nlen);
de = de1;
}
de->file_type = EXT4_FT_UNKNOWN;
@@ -1408,17 +1408,18 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,

/* The 0th block becomes the root, move the dirents out */
fde = &root->dotdot;
- de = (struct ext4_dir_entry_2 *)((char *)fde + le16_to_cpu(fde->rec_len));
+ de = (struct ext4_dir_entry_2 *)((char *)fde +
+ ext4_rec_len_from_disk(fde->rec_len));
len = ((char *) root) + blocksize - (char *) de;
memcpy (data1, de, len);
de = (struct ext4_dir_entry_2 *) data1;
top = data1 + len;
- while ((char *)(de2=(void*)de+le16_to_cpu(de->rec_len)) < top)
+ while ((char *)(de2 = ext4_next_entry(de)) < top)
de = de2;
- de->rec_len = cpu_to_le16(data1 + blocksize - (char *) de);
+ de->rec_len = ext4_rec_len_to_disk(data1 + blocksize - (char *) de);
/* Initialize the root; the dot dirents already exist */
de = (struct ext4_dir_entry_2 *) (&root->dotdot);
- de->rec_len = cpu_to_le16(blocksize - EXT4_DIR_REC_LEN(2));
+ de->rec_len = ext4_rec_len_to_disk(blocksize - EXT4_DIR_REC_LEN(2));
memset (&root->info, 0, sizeof(root->info));
root->info.info_length = sizeof(root->info);
root->info.hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
@@ -1505,7 +1506,7 @@ static int ext4_add_entry (handle_t *handle, struct dentry *dentry,
return retval;
de = (struct ext4_dir_entry_2 *) bh->b_data;
de->inode = 0;
- de->rec_len = cpu_to_le16(blocksize);
+ de->rec_len = ext4_rec_len_to_disk(blocksize);
return add_dirent_to_buf(handle, dentry, inode, de, bh);
}

@@ -1569,7 +1570,7 @@ static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
goto cleanup;
node2 = (struct dx_node *)(bh2->b_data);
entries2 = node2->entries;
- node2->fake.rec_len = cpu_to_le16(sb->s_blocksize);
+ node2->fake.rec_len = ext4_rec_len_to_disk(sb->s_blocksize);
node2->fake.inode = 0;
BUFFER_TRACE(frame->bh, "get_write_access");
err = ext4_journal_get_write_access(handle, frame->bh);
@@ -1668,9 +1669,9 @@ static int ext4_delete_entry (handle_t *handle,
BUFFER_TRACE(bh, "get_write_access");
ext4_journal_get_write_access(handle, bh);
if (pde)
- pde->rec_len =
- cpu_to_le16(le16_to_cpu(pde->rec_len) +
- le16_to_cpu(de->rec_len));
+ pde->rec_len = ext4_rec_len_to_disk(
+ ext4_rec_len_from_disk(pde->rec_len) +
+ ext4_rec_len_from_disk(de->rec_len));
else
de->inode = 0;
dir->i_version++;
@@ -1678,10 +1679,9 @@ static int ext4_delete_entry (handle_t *handle,
ext4_journal_dirty_metadata(handle, bh);
return 0;
}
- i += le16_to_cpu(de->rec_len);
+ i += ext4_rec_len_from_disk(de->rec_len);
pde = de;
- de = (struct ext4_dir_entry_2 *)
- ((char *) de + le16_to_cpu(de->rec_len));
+ de = ext4_next_entry(de);
}
return -ENOENT;
}
@@ -1844,13 +1844,12 @@ retry:
de = (struct ext4_dir_entry_2 *) dir_block->b_data;
de->inode = cpu_to_le32(inode->i_ino);
de->name_len = 1;
- de->rec_len = cpu_to_le16(EXT4_DIR_REC_LEN(de->name_len));
+ de->rec_len = ext4_rec_len_to_disk(EXT4_DIR_REC_LEN(de->name_len));
strcpy (de->name, ".");
ext4_set_de_type(dir->i_sb, de, S_IFDIR);
- de = (struct ext4_dir_entry_2 *)
- ((char *) de + le16_to_cpu(de->rec_len));
+ de = ext4_next_entry(de);
de->inode = cpu_to_le32(dir->i_ino);
- de->rec_len = cpu_to_le16(inode->i_sb->s_blocksize-EXT4_DIR_REC_LEN(1));
+ de->rec_len = ext4_rec_len_to_disk(inode->i_sb->s_blocksize-EXT4_DIR_REC_LEN(1));
de->name_len = 2;
strcpy (de->name, "..");
ext4_set_de_type(dir->i_sb, de, S_IFDIR);
@@ -1902,8 +1901,7 @@ static int empty_dir (struct inode * inode)
return 1;
}
de = (struct ext4_dir_entry_2 *) bh->b_data;
- de1 = (struct ext4_dir_entry_2 *)
- ((char *) de + le16_to_cpu(de->rec_len));
+ de1 = ext4_next_entry(de);
if (le32_to_cpu(de->inode) != inode->i_ino ||
!le32_to_cpu(de1->inode) ||
strcmp (".", de->name) ||
@@ -1914,9 +1912,9 @@ static int empty_dir (struct inode * inode)
brelse (bh);
return 1;
}
- offset = le16_to_cpu(de->rec_len) + le16_to_cpu(de1->rec_len);
- de = (struct ext4_dir_entry_2 *)
- ((char *) de1 + le16_to_cpu(de1->rec_len));
+ offset = ext4_rec_len_from_disk(de->rec_len) +
+ ext4_rec_len_from_disk(de1->rec_len);
+ de = ext4_next_entry(de1);
while (offset < inode->i_size ) {
if (!bh ||
(void *) de >= (void *) (bh->b_data+sb->s_blocksize)) {
@@ -1945,9 +1943,8 @@ static int empty_dir (struct inode * inode)
brelse (bh);
return 0;
}
- offset += le16_to_cpu(de->rec_len);
- de = (struct ext4_dir_entry_2 *)
- ((char *) de + le16_to_cpu(de->rec_len));
+ offset += ext4_rec_len_from_disk(de->rec_len);
+ de = ext4_next_entry(de);
}
brelse (bh);
return 1;
@@ -2302,8 +2299,7 @@ retry:
}

#define PARENT_INO(buffer) \
- ((struct ext4_dir_entry_2 *) ((char *) buffer + \
- le16_to_cpu(((struct ext4_dir_entry_2 *) buffer)->rec_len)))->inode
+ (ext4_next_entry((struct ext4_dir_entry_2 *)(buffer))->inode)

/*
* Anybody can rename anything with this: the permission checks are left to the
diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
index d15a15e..e1caf0a 100644
--- a/include/linux/ext4_fs.h
+++ b/include/linux/ext4_fs.h
@@ -771,6 +771,26 @@ struct ext4_dir_entry_2 {
#define EXT4_DIR_ROUND (EXT4_DIR_PAD - 1)
#define EXT4_DIR_REC_LEN(name_len) (((name_len) + 8 + EXT4_DIR_ROUND) & \
~EXT4_DIR_ROUND)
+#define EXT4_MAX_REC_LEN ((1<<16)-1)
+
+static inline unsigned ext4_rec_len_from_disk(__le16 dlen)
+{
+ unsigned len = le16_to_cpu(dlen);
+
+ if (len == EXT4_MAX_REC_LEN)
+ return 1 << 16;
+ return len;
+}
+
+static inline __le16 ext4_rec_len_to_disk(unsigned len)
+{
+ if (len == (1 << 16))
+ return cpu_to_le16(EXT4_MAX_REC_LEN);
+ else if (len > (1 << 16))
+ BUG();
+ return cpu_to_le16(len);
+}
+
/*
* Hash Tree Directory indexing
* (c) Daniel Phillips, 2001

-
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