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alistair23-linux/fs/affs/super.c
Eric W. Biederman 7f78e03513 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 19:36:31 -08:00

653 lines
15 KiB
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/*
* linux/fs/affs/inode.c
*
* (c) 1996 Hans-Joachim Widmaier - Rewritten
*
* (C) 1993 Ray Burr - Modified for Amiga FFS filesystem.
*
* (C) 1992 Eric Youngdale Modified for ISO 9660 filesystem.
*
* (C) 1991 Linus Torvalds - minix filesystem
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/statfs.h>
#include <linux/parser.h>
#include <linux/magic.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/writeback.h>
#include "affs.h"
extern struct timezone sys_tz;
static int affs_statfs(struct dentry *dentry, struct kstatfs *buf);
static int affs_remount (struct super_block *sb, int *flags, char *data);
static void
affs_commit_super(struct super_block *sb, int wait)
{
struct affs_sb_info *sbi = AFFS_SB(sb);
struct buffer_head *bh = sbi->s_root_bh;
struct affs_root_tail *tail = AFFS_ROOT_TAIL(sb, bh);
lock_buffer(bh);
secs_to_datestamp(get_seconds(), &tail->disk_change);
affs_fix_checksum(sb, bh);
unlock_buffer(bh);
mark_buffer_dirty(bh);
if (wait)
sync_dirty_buffer(bh);
}
static void
affs_put_super(struct super_block *sb)
{
struct affs_sb_info *sbi = AFFS_SB(sb);
pr_debug("AFFS: put_super()\n");
cancel_delayed_work_sync(&sbi->sb_work);
kfree(sbi->s_prefix);
affs_free_bitmap(sb);
affs_brelse(sbi->s_root_bh);
kfree(sbi);
sb->s_fs_info = NULL;
}
static int
affs_sync_fs(struct super_block *sb, int wait)
{
affs_commit_super(sb, wait);
return 0;
}
static void flush_superblock(struct work_struct *work)
{
struct affs_sb_info *sbi;
struct super_block *sb;
sbi = container_of(work, struct affs_sb_info, sb_work.work);
sb = sbi->sb;
spin_lock(&sbi->work_lock);
sbi->work_queued = 0;
spin_unlock(&sbi->work_lock);
affs_commit_super(sb, 1);
}
void affs_mark_sb_dirty(struct super_block *sb)
{
struct affs_sb_info *sbi = AFFS_SB(sb);
unsigned long delay;
if (sb->s_flags & MS_RDONLY)
return;
spin_lock(&sbi->work_lock);
if (!sbi->work_queued) {
delay = msecs_to_jiffies(dirty_writeback_interval * 10);
queue_delayed_work(system_long_wq, &sbi->sb_work, delay);
sbi->work_queued = 1;
}
spin_unlock(&sbi->work_lock);
}
static struct kmem_cache * affs_inode_cachep;
static struct inode *affs_alloc_inode(struct super_block *sb)
{
struct affs_inode_info *i;
i = kmem_cache_alloc(affs_inode_cachep, GFP_KERNEL);
if (!i)
return NULL;
i->vfs_inode.i_version = 1;
i->i_lc = NULL;
i->i_ext_bh = NULL;
i->i_pa_cnt = 0;
return &i->vfs_inode;
}
static void affs_i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
kmem_cache_free(affs_inode_cachep, AFFS_I(inode));
}
static void affs_destroy_inode(struct inode *inode)
{
call_rcu(&inode->i_rcu, affs_i_callback);
}
static void init_once(void *foo)
{
struct affs_inode_info *ei = (struct affs_inode_info *) foo;
sema_init(&ei->i_link_lock, 1);
sema_init(&ei->i_ext_lock, 1);
inode_init_once(&ei->vfs_inode);
}
static int init_inodecache(void)
{
affs_inode_cachep = kmem_cache_create("affs_inode_cache",
sizeof(struct affs_inode_info),
0, (SLAB_RECLAIM_ACCOUNT|
SLAB_MEM_SPREAD),
init_once);
if (affs_inode_cachep == NULL)
return -ENOMEM;
return 0;
}
static void destroy_inodecache(void)
{
/*
* Make sure all delayed rcu free inodes are flushed before we
* destroy cache.
*/
rcu_barrier();
kmem_cache_destroy(affs_inode_cachep);
}
static const struct super_operations affs_sops = {
.alloc_inode = affs_alloc_inode,
.destroy_inode = affs_destroy_inode,
.write_inode = affs_write_inode,
.evict_inode = affs_evict_inode,
.put_super = affs_put_super,
.sync_fs = affs_sync_fs,
.statfs = affs_statfs,
.remount_fs = affs_remount,
.show_options = generic_show_options,
};
enum {
Opt_bs, Opt_mode, Opt_mufs, Opt_prefix, Opt_protect,
Opt_reserved, Opt_root, Opt_setgid, Opt_setuid,
Opt_verbose, Opt_volume, Opt_ignore, Opt_err,
};
static const match_table_t tokens = {
{Opt_bs, "bs=%u"},
{Opt_mode, "mode=%o"},
{Opt_mufs, "mufs"},
{Opt_prefix, "prefix=%s"},
{Opt_protect, "protect"},
{Opt_reserved, "reserved=%u"},
{Opt_root, "root=%u"},
{Opt_setgid, "setgid=%u"},
{Opt_setuid, "setuid=%u"},
{Opt_verbose, "verbose"},
{Opt_volume, "volume=%s"},
{Opt_ignore, "grpquota"},
{Opt_ignore, "noquota"},
{Opt_ignore, "quota"},
{Opt_ignore, "usrquota"},
{Opt_err, NULL},
};
static int
parse_options(char *options, kuid_t *uid, kgid_t *gid, int *mode, int *reserved, s32 *root,
int *blocksize, char **prefix, char *volume, unsigned long *mount_opts)
{
char *p;
substring_t args[MAX_OPT_ARGS];
/* Fill in defaults */
*uid = current_uid();
*gid = current_gid();
*reserved = 2;
*root = -1;
*blocksize = -1;
volume[0] = ':';
volume[1] = 0;
*mount_opts = 0;
if (!options)
return 1;
while ((p = strsep(&options, ",")) != NULL) {
int token, n, option;
if (!*p)
continue;
token = match_token(p, tokens, args);
switch (token) {
case Opt_bs:
if (match_int(&args[0], &n))
return 0;
if (n != 512 && n != 1024 && n != 2048
&& n != 4096) {
printk ("AFFS: Invalid blocksize (512, 1024, 2048, 4096 allowed)\n");
return 0;
}
*blocksize = n;
break;
case Opt_mode:
if (match_octal(&args[0], &option))
return 0;
*mode = option & 0777;
*mount_opts |= SF_SETMODE;
break;
case Opt_mufs:
*mount_opts |= SF_MUFS;
break;
case Opt_prefix:
*prefix = match_strdup(&args[0]);
if (!*prefix)
return 0;
*mount_opts |= SF_PREFIX;
break;
case Opt_protect:
*mount_opts |= SF_IMMUTABLE;
break;
case Opt_reserved:
if (match_int(&args[0], reserved))
return 0;
break;
case Opt_root:
if (match_int(&args[0], root))
return 0;
break;
case Opt_setgid:
if (match_int(&args[0], &option))
return 0;
*gid = make_kgid(current_user_ns(), option);
if (!gid_valid(*gid))
return 0;
*mount_opts |= SF_SETGID;
break;
case Opt_setuid:
if (match_int(&args[0], &option))
return 0;
*uid = make_kuid(current_user_ns(), option);
if (!uid_valid(*uid))
return 0;
*mount_opts |= SF_SETUID;
break;
case Opt_verbose:
*mount_opts |= SF_VERBOSE;
break;
case Opt_volume: {
char *vol = match_strdup(&args[0]);
if (!vol)
return 0;
strlcpy(volume, vol, 32);
kfree(vol);
break;
}
case Opt_ignore:
/* Silently ignore the quota options */
break;
default:
printk("AFFS: Unrecognized mount option \"%s\" "
"or missing value\n", p);
return 0;
}
}
return 1;
}
/* This function definitely needs to be split up. Some fine day I'll
* hopefully have the guts to do so. Until then: sorry for the mess.
*/
static int affs_fill_super(struct super_block *sb, void *data, int silent)
{
struct affs_sb_info *sbi;
struct buffer_head *root_bh = NULL;
struct buffer_head *boot_bh;
struct inode *root_inode = NULL;
s32 root_block;
int size, blocksize;
u32 chksum;
int num_bm;
int i, j;
s32 key;
kuid_t uid;
kgid_t gid;
int reserved;
unsigned long mount_flags;
int tmp_flags; /* fix remount prototype... */
u8 sig[4];
int ret = -EINVAL;
save_mount_options(sb, data);
pr_debug("AFFS: read_super(%s)\n",data ? (const char *)data : "no options");
sb->s_magic = AFFS_SUPER_MAGIC;
sb->s_op = &affs_sops;
sb->s_flags |= MS_NODIRATIME;
sbi = kzalloc(sizeof(struct affs_sb_info), GFP_KERNEL);
if (!sbi)
return -ENOMEM;
sb->s_fs_info = sbi;
sbi->sb = sb;
mutex_init(&sbi->s_bmlock);
spin_lock_init(&sbi->symlink_lock);
spin_lock_init(&sbi->work_lock);
INIT_DELAYED_WORK(&sbi->sb_work, flush_superblock);
if (!parse_options(data,&uid,&gid,&i,&reserved,&root_block,
&blocksize,&sbi->s_prefix,
sbi->s_volume, &mount_flags)) {
printk(KERN_ERR "AFFS: Error parsing options\n");
kfree(sbi->s_prefix);
kfree(sbi);
return -EINVAL;
}
/* N.B. after this point s_prefix must be released */
sbi->s_flags = mount_flags;
sbi->s_mode = i;
sbi->s_uid = uid;
sbi->s_gid = gid;
sbi->s_reserved= reserved;
/* Get the size of the device in 512-byte blocks.
* If we later see that the partition uses bigger
* blocks, we will have to change it.
*/
size = sb->s_bdev->bd_inode->i_size >> 9;
pr_debug("AFFS: initial blocksize=%d, #blocks=%d\n", 512, size);
affs_set_blocksize(sb, PAGE_SIZE);
/* Try to find root block. Its location depends on the block size. */
i = 512;
j = 4096;
if (blocksize > 0) {
i = j = blocksize;
size = size / (blocksize / 512);
}
for (blocksize = i, key = 0; blocksize <= j; blocksize <<= 1, size >>= 1) {
sbi->s_root_block = root_block;
if (root_block < 0)
sbi->s_root_block = (reserved + size - 1) / 2;
pr_debug("AFFS: setting blocksize to %d\n", blocksize);
affs_set_blocksize(sb, blocksize);
sbi->s_partition_size = size;
/* The root block location that was calculated above is not
* correct if the partition size is an odd number of 512-
* byte blocks, which will be rounded down to a number of
* 1024-byte blocks, and if there were an even number of
* reserved blocks. Ideally, all partition checkers should
* report the real number of blocks of the real blocksize,
* but since this just cannot be done, we have to try to
* find the root block anyways. In the above case, it is one
* block behind the calculated one. So we check this one, too.
*/
for (num_bm = 0; num_bm < 2; num_bm++) {
pr_debug("AFFS: Dev %s, trying root=%u, bs=%d, "
"size=%d, reserved=%d\n",
sb->s_id,
sbi->s_root_block + num_bm,
blocksize, size, reserved);
root_bh = affs_bread(sb, sbi->s_root_block + num_bm);
if (!root_bh)
continue;
if (!affs_checksum_block(sb, root_bh) &&
be32_to_cpu(AFFS_ROOT_HEAD(root_bh)->ptype) == T_SHORT &&
be32_to_cpu(AFFS_ROOT_TAIL(sb, root_bh)->stype) == ST_ROOT) {
sbi->s_hashsize = blocksize / 4 - 56;
sbi->s_root_block += num_bm;
key = 1;
goto got_root;
}
affs_brelse(root_bh);
root_bh = NULL;
}
}
if (!silent)
printk(KERN_ERR "AFFS: No valid root block on device %s\n",
sb->s_id);
goto out_error;
/* N.B. after this point bh must be released */
got_root:
root_block = sbi->s_root_block;
/* Find out which kind of FS we have */
boot_bh = sb_bread(sb, 0);
if (!boot_bh) {
printk(KERN_ERR "AFFS: Cannot read boot block\n");
goto out_error;
}
memcpy(sig, boot_bh->b_data, 4);
brelse(boot_bh);
chksum = be32_to_cpu(*(__be32 *)sig);
/* Dircache filesystems are compatible with non-dircache ones
* when reading. As long as they aren't supported, writing is
* not recommended.
*/
if ((chksum == FS_DCFFS || chksum == MUFS_DCFFS || chksum == FS_DCOFS
|| chksum == MUFS_DCOFS) && !(sb->s_flags & MS_RDONLY)) {
printk(KERN_NOTICE "AFFS: Dircache FS - mounting %s read only\n",
sb->s_id);
sb->s_flags |= MS_RDONLY;
}
switch (chksum) {
case MUFS_FS:
case MUFS_INTLFFS:
case MUFS_DCFFS:
sbi->s_flags |= SF_MUFS;
/* fall thru */
case FS_INTLFFS:
case FS_DCFFS:
sbi->s_flags |= SF_INTL;
break;
case MUFS_FFS:
sbi->s_flags |= SF_MUFS;
break;
case FS_FFS:
break;
case MUFS_OFS:
sbi->s_flags |= SF_MUFS;
/* fall thru */
case FS_OFS:
sbi->s_flags |= SF_OFS;
sb->s_flags |= MS_NOEXEC;
break;
case MUFS_DCOFS:
case MUFS_INTLOFS:
sbi->s_flags |= SF_MUFS;
case FS_DCOFS:
case FS_INTLOFS:
sbi->s_flags |= SF_INTL | SF_OFS;
sb->s_flags |= MS_NOEXEC;
break;
default:
printk(KERN_ERR "AFFS: Unknown filesystem on device %s: %08X\n",
sb->s_id, chksum);
goto out_error;
}
if (mount_flags & SF_VERBOSE) {
u8 len = AFFS_ROOT_TAIL(sb, root_bh)->disk_name[0];
printk(KERN_NOTICE "AFFS: Mounting volume \"%.*s\": Type=%.3s\\%c, Blocksize=%d\n",
len > 31 ? 31 : len,
AFFS_ROOT_TAIL(sb, root_bh)->disk_name + 1,
sig, sig[3] + '0', blocksize);
}
sb->s_flags |= MS_NODEV | MS_NOSUID;
sbi->s_data_blksize = sb->s_blocksize;
if (sbi->s_flags & SF_OFS)
sbi->s_data_blksize -= 24;
/* Keep super block in cache */
sbi->s_root_bh = root_bh;
/* N.B. after this point s_root_bh must be released */
tmp_flags = sb->s_flags;
if (affs_init_bitmap(sb, &tmp_flags))
goto out_error;
sb->s_flags = tmp_flags;
/* set up enough so that it can read an inode */
root_inode = affs_iget(sb, root_block);
if (IS_ERR(root_inode)) {
ret = PTR_ERR(root_inode);
goto out_error;
}
if (AFFS_SB(sb)->s_flags & SF_INTL)
sb->s_d_op = &affs_intl_dentry_operations;
else
sb->s_d_op = &affs_dentry_operations;
sb->s_root = d_make_root(root_inode);
if (!sb->s_root) {
printk(KERN_ERR "AFFS: Get root inode failed\n");
goto out_error;
}
pr_debug("AFFS: s_flags=%lX\n",sb->s_flags);
return 0;
/*
* Begin the cascaded cleanup ...
*/
out_error:
kfree(sbi->s_bitmap);
affs_brelse(root_bh);
kfree(sbi->s_prefix);
kfree(sbi);
sb->s_fs_info = NULL;
return ret;
}
static int
affs_remount(struct super_block *sb, int *flags, char *data)
{
struct affs_sb_info *sbi = AFFS_SB(sb);
int blocksize;
kuid_t uid;
kgid_t gid;
int mode;
int reserved;
int root_block;
unsigned long mount_flags;
int res = 0;
char *new_opts = kstrdup(data, GFP_KERNEL);
char volume[32];
char *prefix = NULL;
pr_debug("AFFS: remount(flags=0x%x,opts=\"%s\")\n",*flags,data);
*flags |= MS_NODIRATIME;
memcpy(volume, sbi->s_volume, 32);
if (!parse_options(data, &uid, &gid, &mode, &reserved, &root_block,
&blocksize, &prefix, volume,
&mount_flags)) {
kfree(prefix);
kfree(new_opts);
return -EINVAL;
}
flush_delayed_work(&sbi->sb_work);
replace_mount_options(sb, new_opts);
sbi->s_flags = mount_flags;
sbi->s_mode = mode;
sbi->s_uid = uid;
sbi->s_gid = gid;
/* protect against readers */
spin_lock(&sbi->symlink_lock);
if (prefix) {
kfree(sbi->s_prefix);
sbi->s_prefix = prefix;
}
memcpy(sbi->s_volume, volume, 32);
spin_unlock(&sbi->symlink_lock);
if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
return 0;
if (*flags & MS_RDONLY)
affs_free_bitmap(sb);
else
res = affs_init_bitmap(sb, flags);
return res;
}
static int
affs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct super_block *sb = dentry->d_sb;
int free;
u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
pr_debug("AFFS: statfs() partsize=%d, reserved=%d\n",AFFS_SB(sb)->s_partition_size,
AFFS_SB(sb)->s_reserved);
free = affs_count_free_blocks(sb);
buf->f_type = AFFS_SUPER_MAGIC;
buf->f_bsize = sb->s_blocksize;
buf->f_blocks = AFFS_SB(sb)->s_partition_size - AFFS_SB(sb)->s_reserved;
buf->f_bfree = free;
buf->f_bavail = free;
buf->f_fsid.val[0] = (u32)id;
buf->f_fsid.val[1] = (u32)(id >> 32);
buf->f_namelen = 30;
return 0;
}
static struct dentry *affs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_bdev(fs_type, flags, dev_name, data, affs_fill_super);
}
static struct file_system_type affs_fs_type = {
.owner = THIS_MODULE,
.name = "affs",
.mount = affs_mount,
.kill_sb = kill_block_super,
.fs_flags = FS_REQUIRES_DEV,
};
MODULE_ALIAS_FS("affs");
static int __init init_affs_fs(void)
{
int err = init_inodecache();
if (err)
goto out1;
err = register_filesystem(&affs_fs_type);
if (err)
goto out;
return 0;
out:
destroy_inodecache();
out1:
return err;
}
static void __exit exit_affs_fs(void)
{
unregister_filesystem(&affs_fs_type);
destroy_inodecache();
}
MODULE_DESCRIPTION("Amiga filesystem support for Linux");
MODULE_LICENSE("GPL");
module_init(init_affs_fs)
module_exit(exit_affs_fs)
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