OpenCloudOS-Kernel/fs/fat/namei_msdos.c

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/*
* linux/fs/msdos/namei.c
*
* Written 1992,1993 by Werner Almesberger
* Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
* Rewritten for constant inumbers 1999 by Al Viro
*/
#include <linux/module.h>
#include "fat.h"
/* Characters that are undesirable in an MS-DOS file name */
static unsigned char bad_chars[] = "*?<>|\"";
static unsigned char bad_if_strict[] = "+=,; ";
/***** Formats an MS-DOS file name. Rejects invalid names. */
static int msdos_format_name(const unsigned char *name, int len,
unsigned char *res, struct fat_mount_options *opts)
/*
* name is the proposed name, len is its length, res is
* the resulting name, opts->name_check is either (r)elaxed,
* (n)ormal or (s)trict, opts->dotsOK allows dots at the
* beginning of name (for hidden files)
*/
{
unsigned char *walk;
unsigned char c;
int space;
if (name[0] == '.') { /* dotfile because . and .. already done */
if (opts->dotsOK) {
/* Get rid of dot - test for it elsewhere */
name++;
len--;
} else
return -EINVAL;
}
/*
* disallow names that _really_ start with a dot
*/
space = 1;
c = 0;
for (walk = res; len && walk - res < 8; walk++) {
c = *name++;
len--;
if (opts->name_check != 'r' && strchr(bad_chars, c))
return -EINVAL;
if (opts->name_check == 's' && strchr(bad_if_strict, c))
return -EINVAL;
if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
return -EINVAL;
if (c < ' ' || c == ':' || c == '\\')
return -EINVAL;
/*
* 0xE5 is legal as a first character, but we must substitute
* 0x05 because 0xE5 marks deleted files. Yes, DOS really
* does this.
* It seems that Microsoft hacked DOS to support non-US
* characters after the 0xE5 character was already in use to
* mark deleted files.
*/
if ((res == walk) && (c == 0xE5))
c = 0x05;
if (c == '.')
break;
space = (c == ' ');
*walk = (!opts->nocase && c >= 'a' && c <= 'z') ? c - 32 : c;
}
if (space)
return -EINVAL;
if (opts->name_check == 's' && len && c != '.') {
c = *name++;
len--;
if (c != '.')
return -EINVAL;
}
while (c != '.' && len--)
c = *name++;
if (c == '.') {
while (walk - res < 8)
*walk++ = ' ';
while (len > 0 && walk - res < MSDOS_NAME) {
c = *name++;
len--;
if (opts->name_check != 'r' && strchr(bad_chars, c))
return -EINVAL;
if (opts->name_check == 's' &&
strchr(bad_if_strict, c))
return -EINVAL;
if (c < ' ' || c == ':' || c == '\\')
return -EINVAL;
if (c == '.') {
if (opts->name_check == 's')
return -EINVAL;
break;
}
if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
return -EINVAL;
space = c == ' ';
if (!opts->nocase && c >= 'a' && c <= 'z')
*walk++ = c - 32;
else
*walk++ = c;
}
if (space)
return -EINVAL;
if (opts->name_check == 's' && len)
return -EINVAL;
}
while (walk - res < MSDOS_NAME)
*walk++ = ' ';
return 0;
}
/***** Locates a directory entry. Uses unformatted name. */
static int msdos_find(struct inode *dir, const unsigned char *name, int len,
struct fat_slot_info *sinfo)
{
struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
unsigned char msdos_name[MSDOS_NAME];
int err;
err = msdos_format_name(name, len, msdos_name, &sbi->options);
if (err)
return -ENOENT;
err = fat_scan(dir, msdos_name, sinfo);
if (!err && sbi->options.dotsOK) {
if (name[0] == '.') {
if (!(sinfo->de->attr & ATTR_HIDDEN))
err = -ENOENT;
} else {
if (sinfo->de->attr & ATTR_HIDDEN)
err = -ENOENT;
}
if (err)
brelse(sinfo->bh);
}
return err;
}
/*
* Compute the hash for the msdos name corresponding to the dentry.
* Note: if the name is invalid, we leave the hash code unchanged so
* that the existing dentry can be used. The msdos fs routines will
* return ENOENT or EINVAL as appropriate.
*/
static int msdos_hash(const struct dentry *dentry, struct qstr *qstr)
{
struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
unsigned char msdos_name[MSDOS_NAME];
int error;
error = msdos_format_name(qstr->name, qstr->len, msdos_name, options);
if (!error)
qstr->hash = full_name_hash(dentry, msdos_name, MSDOS_NAME);
return 0;
}
/*
* Compare two msdos names. If either of the names are invalid,
* we fall back to doing the standard name comparison.
*/
static int msdos_cmp(const struct dentry *dentry,
unsigned int len, const char *str, const struct qstr *name)
{
struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
unsigned char a_msdos_name[MSDOS_NAME], b_msdos_name[MSDOS_NAME];
int error;
error = msdos_format_name(name->name, name->len, a_msdos_name, options);
if (error)
goto old_compare;
error = msdos_format_name(str, len, b_msdos_name, options);
if (error)
goto old_compare;
error = memcmp(a_msdos_name, b_msdos_name, MSDOS_NAME);
out:
return error;
old_compare:
error = 1;
if (name->len == len)
error = memcmp(name->name, str, len);
goto out;
}
static const struct dentry_operations msdos_dentry_operations = {
.d_hash = msdos_hash,
.d_compare = msdos_cmp,
};
/*
* AV. Wrappers for FAT sb operations. Is it wise?
*/
/***** Get inode using directory and name */
static struct dentry *msdos_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
struct super_block *sb = dir->i_sb;
struct fat_slot_info sinfo;
struct inode *inode;
int err;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
switch (err) {
case -ENOENT:
inode = NULL;
break;
case 0:
inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
brelse(sinfo.bh);
break;
default:
inode = ERR_PTR(err);
}
mutex_unlock(&MSDOS_SB(sb)->s_lock);
return d_splice_alias(inode, dentry);
}
/***** Creates a directory entry (name is already formatted). */
static int msdos_add_entry(struct inode *dir, const unsigned char *name,
int is_dir, int is_hid, int cluster,
struct timespec *ts, struct fat_slot_info *sinfo)
{
fatfs: add UTC timestamp option Provide a new mount option ("tz=UTC") for DOS (vfat/msdos) filesystems, allowing timestamps to be in coordinated universal time (UTC) rather than local time in applications where doing this is advantageous. In particular, portable devices that use fat/vfat (such as digital cameras) can benefit from using UTC in their internal clocks, thus avoiding daylight saving time errors and general time ambiguity issues. The user of the device does not have to worry about changing the time when moving from place or when daylight saving changes. The new mount option, when set, disables the counter-adjustment that Linux currently makes to FAT timestamp info in anticipation of the normal userspace time zone correction. When used in this new mode, all daylight saving time and time zone handling is done in userspace as is normal for many other filesystems (like ext3). The default mode, which remains unchanged, is still appropriate when mounting volumes written in Windows (because of its use of local time). I originally based this patch on one submitted last year by Paul Collins, but I updated it to work with current source and changed variable/option naming. Ogawa Hirofumi (who maintains these filesystems) and I discussed this patch at length on lkml, and he suggested using the option name in the attached version of the patch. Barry Bouwsma pointed out a good addition to the patch as well. Signed-off-by: Joe Peterson <joe@skyrush.com> Signed-off-by: Paul Collins <paul@ondioline.org> Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Cc: Barry Bouwsma <free_beer_for_all@yahoo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-25 16:46:47 +08:00
struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
struct msdos_dir_entry de;
__le16 time, date;
int err;
memcpy(de.name, name, MSDOS_NAME);
de.attr = is_dir ? ATTR_DIR : ATTR_ARCH;
if (is_hid)
de.attr |= ATTR_HIDDEN;
de.lcase = 0;
fat_time_unix2fat(sbi, ts, &time, &date, NULL);
de.cdate = de.adate = 0;
de.ctime = 0;
de.ctime_cs = 0;
de.time = time;
de.date = date;
fat_set_start(&de, cluster);
de.size = 0;
err = fat_add_entries(dir, &de, 1, sinfo);
if (err)
return err;
dir->i_ctime = dir->i_mtime = *ts;
if (IS_DIRSYNC(dir))
(void)fat_sync_inode(dir);
else
mark_inode_dirty(dir);
return 0;
}
/***** Create a file */
static int msdos_create(struct inode *dir, struct dentry *dentry, umode_t mode,
bool excl)
{
struct super_block *sb = dir->i_sb;
struct inode *inode = NULL;
struct fat_slot_info sinfo;
struct timespec ts;
unsigned char msdos_name[MSDOS_NAME];
int err, is_hid;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
msdos_name, &MSDOS_SB(sb)->options);
if (err)
goto out;
is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
/* Have to do it due to foo vs. .foo conflicts */
if (!fat_scan(dir, msdos_name, &sinfo)) {
brelse(sinfo.bh);
err = -EINVAL;
goto out;
}
ts = current_time(dir);
err = msdos_add_entry(dir, msdos_name, 0, is_hid, 0, &ts, &sinfo);
if (err)
goto out;
inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
brelse(sinfo.bh);
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
goto out;
}
inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
/* timestamp is already written, so mark_inode_dirty() is unneeded. */
d_instantiate(dentry, inode);
out:
mutex_unlock(&MSDOS_SB(sb)->s_lock);
if (!err)
err = fat_flush_inodes(sb, dir, inode);
return err;
}
/***** Remove a directory */
static int msdos_rmdir(struct inode *dir, struct dentry *dentry)
{
struct super_block *sb = dir->i_sb;
struct inode *inode = d_inode(dentry);
struct fat_slot_info sinfo;
int err;
mutex_lock(&MSDOS_SB(sb)->s_lock);
/*
* Check whether the directory is not in use, then check
* whether it is empty.
*/
err = fat_dir_empty(inode);
if (err)
goto out;
err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
if (err)
goto out;
err = fat_remove_entries(dir, &sinfo); /* and releases bh */
if (err)
goto out;
drop_nlink(dir);
clear_nlink(inode);
inode->i_ctime = current_time(inode);
fat_detach(inode);
out:
mutex_unlock(&MSDOS_SB(sb)->s_lock);
if (!err)
err = fat_flush_inodes(sb, dir, inode);
return err;
}
/***** Make a directory */
static int msdos_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
struct super_block *sb = dir->i_sb;
struct fat_slot_info sinfo;
struct inode *inode;
unsigned char msdos_name[MSDOS_NAME];
struct timespec ts;
int err, is_hid, cluster;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
msdos_name, &MSDOS_SB(sb)->options);
if (err)
goto out;
is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
/* foo vs .foo situation */
if (!fat_scan(dir, msdos_name, &sinfo)) {
brelse(sinfo.bh);
err = -EINVAL;
goto out;
}
ts = current_time(dir);
cluster = fat_alloc_new_dir(dir, &ts);
if (cluster < 0) {
err = cluster;
goto out;
}
err = msdos_add_entry(dir, msdos_name, 1, is_hid, cluster, &ts, &sinfo);
if (err)
goto out_free;
inc_nlink(dir);
inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
brelse(sinfo.bh);
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
/* the directory was completed, just return a error */
goto out;
}
set_nlink(inode, 2);
inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
/* timestamp is already written, so mark_inode_dirty() is unneeded. */
d_instantiate(dentry, inode);
mutex_unlock(&MSDOS_SB(sb)->s_lock);
fat_flush_inodes(sb, dir, inode);
return 0;
out_free:
fat_free_clusters(dir, cluster);
out:
mutex_unlock(&MSDOS_SB(sb)->s_lock);
return err;
}
/***** Unlink a file */
static int msdos_unlink(struct inode *dir, struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
struct super_block *sb = inode->i_sb;
struct fat_slot_info sinfo;
int err;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
if (err)
goto out;
err = fat_remove_entries(dir, &sinfo); /* and releases bh */
if (err)
goto out;
clear_nlink(inode);
inode->i_ctime = current_time(inode);
fat_detach(inode);
out:
mutex_unlock(&MSDOS_SB(sb)->s_lock);
if (!err)
err = fat_flush_inodes(sb, dir, inode);
return err;
}
static int do_msdos_rename(struct inode *old_dir, unsigned char *old_name,
struct dentry *old_dentry,
struct inode *new_dir, unsigned char *new_name,
struct dentry *new_dentry, int is_hid)
{
struct buffer_head *dotdot_bh;
struct msdos_dir_entry *dotdot_de;
struct inode *old_inode, *new_inode;
struct fat_slot_info old_sinfo, sinfo;
struct timespec ts;
loff_t new_i_pos;
int err, old_attrs, is_dir, update_dotdot, corrupt = 0;
old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
old_inode = d_inode(old_dentry);
new_inode = d_inode(new_dentry);
err = fat_scan(old_dir, old_name, &old_sinfo);
if (err) {
err = -EIO;
goto out;
}
is_dir = S_ISDIR(old_inode->i_mode);
update_dotdot = (is_dir && old_dir != new_dir);
if (update_dotdot) {
if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
err = -EIO;
goto out;
}
}
old_attrs = MSDOS_I(old_inode)->i_attrs;
err = fat_scan(new_dir, new_name, &sinfo);
if (!err) {
if (!new_inode) {
/* "foo" -> ".foo" case. just change the ATTR_HIDDEN */
if (sinfo.de != old_sinfo.de) {
err = -EINVAL;
goto out;
}
if (is_hid)
MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
else
MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
if (IS_DIRSYNC(old_dir)) {
err = fat_sync_inode(old_inode);
if (err) {
MSDOS_I(old_inode)->i_attrs = old_attrs;
goto out;
}
} else
mark_inode_dirty(old_inode);
old_dir->i_version++;
old_dir->i_ctime = old_dir->i_mtime = current_time(old_dir);
if (IS_DIRSYNC(old_dir))
(void)fat_sync_inode(old_dir);
else
mark_inode_dirty(old_dir);
goto out;
}
}
ts = current_time(old_inode);
if (new_inode) {
if (err)
goto out;
if (is_dir) {
err = fat_dir_empty(new_inode);
if (err)
goto out;
}
new_i_pos = MSDOS_I(new_inode)->i_pos;
fat_detach(new_inode);
} else {
err = msdos_add_entry(new_dir, new_name, is_dir, is_hid, 0,
&ts, &sinfo);
if (err)
goto out;
new_i_pos = sinfo.i_pos;
}
new_dir->i_version++;
fat_detach(old_inode);
fat_attach(old_inode, new_i_pos);
if (is_hid)
MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
else
MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
if (IS_DIRSYNC(new_dir)) {
err = fat_sync_inode(old_inode);
if (err)
goto error_inode;
} else
mark_inode_dirty(old_inode);
if (update_dotdot) {
fat_set_start(dotdot_de, MSDOS_I(new_dir)->i_logstart);
mark_buffer_dirty_inode(dotdot_bh, old_inode);
if (IS_DIRSYNC(new_dir)) {
err = sync_dirty_buffer(dotdot_bh);
if (err)
goto error_dotdot;
}
drop_nlink(old_dir);
if (!new_inode)
inc_nlink(new_dir);
}
err = fat_remove_entries(old_dir, &old_sinfo); /* and releases bh */
old_sinfo.bh = NULL;
if (err)
goto error_dotdot;
old_dir->i_version++;
old_dir->i_ctime = old_dir->i_mtime = ts;
if (IS_DIRSYNC(old_dir))
(void)fat_sync_inode(old_dir);
else
mark_inode_dirty(old_dir);
if (new_inode) {
drop_nlink(new_inode);
if (is_dir)
drop_nlink(new_inode);
new_inode->i_ctime = ts;
}
out:
brelse(sinfo.bh);
brelse(dotdot_bh);
brelse(old_sinfo.bh);
return err;
error_dotdot:
/* data cluster is shared, serious corruption */
corrupt = 1;
if (update_dotdot) {
fat_set_start(dotdot_de, MSDOS_I(old_dir)->i_logstart);
mark_buffer_dirty_inode(dotdot_bh, old_inode);
corrupt |= sync_dirty_buffer(dotdot_bh);
}
error_inode:
fat_detach(old_inode);
fat_attach(old_inode, old_sinfo.i_pos);
MSDOS_I(old_inode)->i_attrs = old_attrs;
if (new_inode) {
fat_attach(new_inode, new_i_pos);
if (corrupt)
corrupt |= fat_sync_inode(new_inode);
} else {
/*
* If new entry was not sharing the data cluster, it
* shouldn't be serious corruption.
*/
int err2 = fat_remove_entries(new_dir, &sinfo);
if (corrupt)
corrupt |= err2;
sinfo.bh = NULL;
}
if (corrupt < 0) {
fat_fs_error(new_dir->i_sb,
"%s: Filesystem corrupted (i_pos %lld)",
__func__, sinfo.i_pos);
}
goto out;
}
/***** Rename, a wrapper for rename_same_dir & rename_diff_dir */
static int msdos_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry,
unsigned int flags)
{
struct super_block *sb = old_dir->i_sb;
unsigned char old_msdos_name[MSDOS_NAME], new_msdos_name[MSDOS_NAME];
int err, is_hid;
if (flags & ~RENAME_NOREPLACE)
return -EINVAL;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = msdos_format_name(old_dentry->d_name.name,
old_dentry->d_name.len, old_msdos_name,
&MSDOS_SB(old_dir->i_sb)->options);
if (err)
goto out;
err = msdos_format_name(new_dentry->d_name.name,
new_dentry->d_name.len, new_msdos_name,
&MSDOS_SB(new_dir->i_sb)->options);
if (err)
goto out;
is_hid =
(new_dentry->d_name.name[0] == '.') && (new_msdos_name[0] != '.');
err = do_msdos_rename(old_dir, old_msdos_name, old_dentry,
new_dir, new_msdos_name, new_dentry, is_hid);
out:
mutex_unlock(&MSDOS_SB(sb)->s_lock);
if (!err)
err = fat_flush_inodes(sb, old_dir, new_dir);
return err;
}
static const struct inode_operations msdos_dir_inode_operations = {
.create = msdos_create,
.lookup = msdos_lookup,
.unlink = msdos_unlink,
.mkdir = msdos_mkdir,
.rmdir = msdos_rmdir,
.rename = msdos_rename,
.setattr = fat_setattr,
.getattr = fat_getattr,
};
static void setup(struct super_block *sb)
{
MSDOS_SB(sb)->dir_ops = &msdos_dir_inode_operations;
sb->s_d_op = &msdos_dentry_operations;
sb->s_flags |= MS_NOATIME;
}
static int msdos_fill_super(struct super_block *sb, void *data, int silent)
{
return fat_fill_super(sb, data, silent, 0, setup);
}
static struct dentry *msdos_mount(struct file_system_type *fs_type,
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 17:02:57 +08:00
int flags, const char *dev_name,
void *data)
{
return mount_bdev(fs_type, flags, dev_name, data, msdos_fill_super);
}
static struct file_system_type msdos_fs_type = {
.owner = THIS_MODULE,
.name = "msdos",
.mount = msdos_mount,
.kill_sb = kill_block_super,
.fs_flags = FS_REQUIRES_DEV,
};
fs: Limit sys_mount to only request filesystem modules. Modify the request_module to prefix the file system type with "fs-" and add aliases to all of the filesystems that can be built as modules to match. A common practice is to build all of the kernel code and leave code that is not commonly needed as modules, with the result that many users are exposed to any bug anywhere in the kernel. Looking for filesystems with a fs- prefix limits the pool of possible modules that can be loaded by mount to just filesystems trivially making things safer with no real cost. Using aliases means user space can control the policy of which filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf with blacklist and alias directives. Allowing simple, safe, well understood work-arounds to known problematic software. This also addresses a rare but unfortunate problem where the filesystem name is not the same as it's module name and module auto-loading would not work. While writing this patch I saw a handful of such cases. The most significant being autofs that lives in the module autofs4. This is relevant to user namespaces because we can reach the request module in get_fs_type() without having any special permissions, and people get uncomfortable when a user specified string (in this case the filesystem type) goes all of the way to request_module. After having looked at this issue I don't think there is any particular reason to perform any filtering or permission checks beyond making it clear in the module request that we want a filesystem module. The common pattern in the kernel is to call request_module() without regards to the users permissions. In general all a filesystem module does once loaded is call register_filesystem() and go to sleep. Which means there is not much attack surface exposed by loading a filesytem module unless the filesystem is mounted. In a user namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT, which most filesystems do not set today. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Acked-by: Kees Cook <keescook@chromium.org> Reported-by: Kees Cook <keescook@google.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-03-03 11:39:14 +08:00
MODULE_ALIAS_FS("msdos");
static int __init init_msdos_fs(void)
{
return register_filesystem(&msdos_fs_type);
}
static void __exit exit_msdos_fs(void)
{
unregister_filesystem(&msdos_fs_type);
}
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Werner Almesberger");
MODULE_DESCRIPTION("MS-DOS filesystem support");
module_init(init_msdos_fs)
module_exit(exit_msdos_fs)