hfsplus: fix worst-case unicode to char conversion of file names and attributes

This is a series of 3 patches which corrects issues in HFS+ concerning
the use of non-english file names and attributes.  Names and attributes
are stored internally as UTF-16 units up to a fixed maximum size, and
convert to and from user-representation by NLS.  The code incorrectly
assume that NLS string lengths are equal to unicode lengths, which is
only true for English ascii usage.

This patch (of 3):

The HFS Plus Volume Format specification (TN1150) states that file names
are stored internally as a maximum of 255 unicode characters, as defined
by The Unicode Standard, Version 2.0 [Unicode, Inc.  ISBN
0-201-48345-9].  File names are converted by the NLS system on Linux
before presented to the user.

255 CJK characters converts to UTF-8 with 1 unicode character to up to 3
bytes, and to GB18030 with 1 unicode character to up to 4 bytes.  Thus,
trying in a UTF-8 locale to list files with names of more than 85 CJK
characters results in:

    $ ls /mnt
    ls: reading directory /mnt: File name too long

The receiving buffer to hfsplus_uni2asc() needs to be 255 x
NLS_MAX_CHARSET_SIZE bytes, not 255 bytes as the code has always been.

Similar consideration applies to attributes, which are stored internally
as a maximum of 127 UTF-16BE units.  See XNU source for an up-to-date
reference on attributes.

Strictly speaking, the maximum value of NLS_MAX_CHARSET_SIZE = 6 is not
attainable in the case of conversion to UTF-8, as going beyond 3 bytes
requires the use of surrogate pairs, i.e.  consuming two input units.

Thanks Anton Altaparmakov for reviewing an earlier version of this
change.

This patch fixes all callers of hfsplus_uni2asc(), and also enables the
use of long non-English file names in HFS+.  The getting and setting,
and general usage of long non-English attributes requires further
forthcoming work, in the following patches of this series.

[akpm@linux-foundation.org: fix build]
Signed-off-by: Hin-Tak Leung <htl10@users.sourceforge.net>
Reviewed-by: Anton Altaparmakov <anton@tuxera.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Sougata Santra <sougata@tuxera.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 21 insertions, 5 deletions

diff --git a/fs/hfsplus/dir.c b/fs/hfsplus/dir.c
index bdec66522de3..fb07d260e692 100644
--- a/fs/hfsplus/dir.c
+++ b/fs/hfsplus/dir.c
@@ -12,6 +12,7 @@
 #include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/random.h>
+#include <linux/nls.h>
 
 #include "hfsplus_fs.h"
 #include "hfsplus_raw.h"
@@ -127,7 +128,7 @@ static int hfsplus_readdir(struct file *file, struct dir_context *ctx)
         struct inode *inode = file_inode(file);
         struct super_block *sb = inode->i_sb;
         int len, err;
-        char strbuf[HFSPLUS_MAX_STRLEN + 1];
+        char *strbuf;
         hfsplus_cat_entry entry;
         struct hfs_find_data fd;
         struct hfsplus_readdir_data *rd;
@@ -139,6 +140,11 @@ static int hfsplus_readdir(struct file *file, struct dir_context *ctx)
         err = hfs_find_init(HFSPLUS_SB(sb)->cat_tree, &fd);
         if (err)
                 return err;
+        strbuf = kmalloc(NLS_MAX_CHARSET_SIZE * HFSPLUS_MAX_STRLEN + 1, GFP_KERNEL);
+        if (!strbuf) {
+                err = -ENOMEM;
+                goto out;
+        }
         hfsplus_cat_build_key(sb, fd.search_key, inode->i_ino, NULL);
         err = hfs_brec_find(&fd, hfs_find_rec_by_key);
         if (err)
@@ -193,7 +199,7 @@ static int hfsplus_readdir(struct file *file, struct dir_context *ctx)
                 hfs_bnode_read(fd.bnode, &entry, fd.entryoffset,
                         fd.entrylength);
                 type = be16_to_cpu(entry.type);
-                len = HFSPLUS_MAX_STRLEN;
+                len = NLS_MAX_CHARSET_SIZE * HFSPLUS_MAX_STRLEN;
                 err = hfsplus_uni2asc(sb, &fd.key->cat.name, strbuf, &len);
                 if (err)
                         goto out;
@@ -246,6 +252,7 @@ next:
         }
         memcpy(&rd->key, fd.key, sizeof(struct hfsplus_cat_key));
 out:
+        kfree(strbuf);
         hfs_find_exit(&fd);
         return err;
 }
diff --git a/fs/hfsplus/xattr.c b/fs/hfsplus/xattr.c
index 4e27edc082a4..e2b3c9ea1c71 100644
--- a/fs/hfsplus/xattr.c
+++ b/fs/hfsplus/xattr.c
@@ -8,6 +8,7 @@
 
 #include "hfsplus_fs.h"
 #include <linux/posix_acl_xattr.h>
+#include <linux/nls.h>
 #include "xattr.h"
 #include "acl.h"
 
@@ -645,8 +646,7 @@ ssize_t hfsplus_listxattr(struct dentry *dentry, char *buffer, size_t size)
         struct hfs_find_data fd;
         u16 key_len = 0;
         struct hfsplus_attr_key attr_key;
-        char strbuf[HFSPLUS_ATTR_MAX_STRLEN +
-                        XATTR_MAC_OSX_PREFIX_LEN + 1] = {0};
+        char *strbuf;
         int xattr_name_len;
 
         if ((!S_ISREG(inode->i_mode) &&
@@ -666,6 +666,13 @@ ssize_t hfsplus_listxattr(struct dentry *dentry, char *buffer, size_t size)
                 return err;
         }
 
+        strbuf = kmalloc(NLS_MAX_CHARSET_SIZE * HFSPLUS_ATTR_MAX_STRLEN +
+                        XATTR_MAC_OSX_PREFIX_LEN + 1, GFP_KERNEL);
+        if (!strbuf) {
+                res = -ENOMEM;
+                goto out;
+        }
+
         err = hfsplus_find_attr(inode->i_sb, inode->i_ino, NULL, &fd);
         if (err) {
                 if (err == -ENOENT) {
@@ -692,7 +699,7 @@ ssize_t hfsplus_listxattr(struct dentry *dentry, char *buffer, size_t size)
                 if (be32_to_cpu(attr_key.cnid) != inode->i_ino)
                         goto end_listxattr;
 
-                xattr_name_len = HFSPLUS_ATTR_MAX_STRLEN;
+                xattr_name_len = NLS_MAX_CHARSET_SIZE * HFSPLUS_ATTR_MAX_STRLEN;
                 if (hfsplus_uni2asc(inode->i_sb,
                         (const struct hfsplus_unistr *)&fd.key->attr.key_name,
                                         strbuf, &xattr_name_len)) {
@@ -718,6 +725,8 @@ ssize_t hfsplus_listxattr(struct dentry *dentry, char *buffer, size_t size)
         }
 
 end_listxattr:
+        kfree(strbuf);
+out:
         hfs_find_exit(&fd);
         return res;
 }