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ext2: avoid rec_len overflow with 64KB block size
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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>
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@jankara
jankara authored and Linus Torvalds committed Oct 22, 2007
1 parent 321bcf9 commit 89910cc
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Showing 2 changed files with 33 additions and 12 deletions.
44 changes: 32 additions & 12 deletions fs/ext2/dir.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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);
}
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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;
}
Expand All @@ -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)
Expand All @@ -518,8 +537,8 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
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;
Expand Down Expand Up @@ -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);
Expand All @@ -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;
Expand Down Expand Up @@ -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);
Expand Down
1 change: 1 addition & 0 deletions include/linux/ext2_fs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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)
Expand Down

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