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linux-next/fs/logfs/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

654 lines
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/*
* fs/logfs/super.c
*
* As should be obvious for Linux kernel code, license is GPLv2
*
* Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
*
* Generally contains mount/umount code and also serves as a dump area for
* any functions that don't fit elsewhere and neither justify a file of their
* own.
*/
#include "logfs.h"
#include <linux/bio.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/mtd/mtd.h>
#include <linux/statfs.h>
#include <linux/buffer_head.h>
static DEFINE_MUTEX(emergency_mutex);
static struct page *emergency_page;
struct page *emergency_read_begin(struct address_space *mapping, pgoff_t index)
{
filler_t *filler = (filler_t *)mapping->a_ops->readpage;
struct page *page;
int err;
page = read_cache_page(mapping, index, filler, NULL);
if (page)
return page;
/* No more pages available, switch to emergency page */
printk(KERN_INFO"Logfs: Using emergency page\n");
mutex_lock(&emergency_mutex);
err = filler(NULL, emergency_page);
if (err) {
mutex_unlock(&emergency_mutex);
printk(KERN_EMERG"Logfs: Error reading emergency page\n");
return ERR_PTR(err);
}
return emergency_page;
}
void emergency_read_end(struct page *page)
{
if (page == emergency_page)
mutex_unlock(&emergency_mutex);
else
page_cache_release(page);
}
static void dump_segfile(struct super_block *sb)
{
struct logfs_super *super = logfs_super(sb);
struct logfs_segment_entry se;
u32 segno;
for (segno = 0; segno < super->s_no_segs; segno++) {
logfs_get_segment_entry(sb, segno, &se);
printk("%3x: %6x %8x", segno, be32_to_cpu(se.ec_level),
be32_to_cpu(se.valid));
if (++segno < super->s_no_segs) {
logfs_get_segment_entry(sb, segno, &se);
printk(" %6x %8x", be32_to_cpu(se.ec_level),
be32_to_cpu(se.valid));
}
if (++segno < super->s_no_segs) {
logfs_get_segment_entry(sb, segno, &se);
printk(" %6x %8x", be32_to_cpu(se.ec_level),
be32_to_cpu(se.valid));
}
if (++segno < super->s_no_segs) {
logfs_get_segment_entry(sb, segno, &se);
printk(" %6x %8x", be32_to_cpu(se.ec_level),
be32_to_cpu(se.valid));
}
printk("\n");
}
}
/*
* logfs_crash_dump - dump debug information to device
*
* The LogFS superblock only occupies part of a segment. This function will
* write as much debug information as it can gather into the spare space.
*/
void logfs_crash_dump(struct super_block *sb)
{
dump_segfile(sb);
}
/*
* FIXME: There should be a reserve for root, similar to ext2.
*/
int logfs_statfs(struct dentry *dentry, struct kstatfs *stats)
{
struct super_block *sb = dentry->d_sb;
struct logfs_super *super = logfs_super(sb);
stats->f_type = LOGFS_MAGIC_U32;
stats->f_bsize = sb->s_blocksize;
stats->f_blocks = super->s_size >> LOGFS_BLOCK_BITS >> 3;
stats->f_bfree = super->s_free_bytes >> sb->s_blocksize_bits;
stats->f_bavail = super->s_free_bytes >> sb->s_blocksize_bits;
stats->f_files = 0;
stats->f_ffree = 0;
stats->f_namelen = LOGFS_MAX_NAMELEN;
return 0;
}
static int logfs_sb_set(struct super_block *sb, void *_super)
{
struct logfs_super *super = _super;
sb->s_fs_info = super;
sb->s_mtd = super->s_mtd;
sb->s_bdev = super->s_bdev;
#ifdef CONFIG_BLOCK
if (sb->s_bdev)
sb->s_bdi = &bdev_get_queue(sb->s_bdev)->backing_dev_info;
#endif
#ifdef CONFIG_MTD
if (sb->s_mtd)
sb->s_bdi = sb->s_mtd->backing_dev_info;
#endif
return 0;
}
static int logfs_sb_test(struct super_block *sb, void *_super)
{
struct logfs_super *super = _super;
struct mtd_info *mtd = super->s_mtd;
if (mtd && sb->s_mtd == mtd)
return 1;
if (super->s_bdev && sb->s_bdev == super->s_bdev)
return 1;
return 0;
}
static void set_segment_header(struct logfs_segment_header *sh, u8 type,
u8 level, u32 segno, u32 ec)
{
sh->pad = 0;
sh->type = type;
sh->level = level;
sh->segno = cpu_to_be32(segno);
sh->ec = cpu_to_be32(ec);
sh->gec = cpu_to_be64(segno);
sh->crc = logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4);
}
static void logfs_write_ds(struct super_block *sb, struct logfs_disk_super *ds,
u32 segno, u32 ec)
{
struct logfs_super *super = logfs_super(sb);
struct logfs_segment_header *sh = &ds->ds_sh;
int i;
memset(ds, 0, sizeof(*ds));
set_segment_header(sh, SEG_SUPER, 0, segno, ec);
ds->ds_ifile_levels = super->s_ifile_levels;
ds->ds_iblock_levels = super->s_iblock_levels;
ds->ds_data_levels = super->s_data_levels; /* XXX: Remove */
ds->ds_segment_shift = super->s_segshift;
ds->ds_block_shift = sb->s_blocksize_bits;
ds->ds_write_shift = super->s_writeshift;
ds->ds_filesystem_size = cpu_to_be64(super->s_size);
ds->ds_segment_size = cpu_to_be32(super->s_segsize);
ds->ds_bad_seg_reserve = cpu_to_be32(super->s_bad_seg_reserve);
ds->ds_feature_incompat = cpu_to_be64(super->s_feature_incompat);
ds->ds_feature_ro_compat= cpu_to_be64(super->s_feature_ro_compat);
ds->ds_feature_compat = cpu_to_be64(super->s_feature_compat);
ds->ds_feature_flags = cpu_to_be64(super->s_feature_flags);
ds->ds_root_reserve = cpu_to_be64(super->s_root_reserve);
ds->ds_speed_reserve = cpu_to_be64(super->s_speed_reserve);
journal_for_each(i)
ds->ds_journal_seg[i] = cpu_to_be32(super->s_journal_seg[i]);
ds->ds_magic = cpu_to_be64(LOGFS_MAGIC);
ds->ds_crc = logfs_crc32(ds, sizeof(*ds),
LOGFS_SEGMENT_HEADERSIZE + 12);
}
static int write_one_sb(struct super_block *sb,
struct page *(*find_sb)(struct super_block *sb, u64 *ofs))
{
struct logfs_super *super = logfs_super(sb);
struct logfs_disk_super *ds;
struct logfs_segment_entry se;
struct page *page;
u64 ofs;
u32 ec, segno;
int err;
page = find_sb(sb, &ofs);
if (!page)
return -EIO;
ds = page_address(page);
segno = seg_no(sb, ofs);
logfs_get_segment_entry(sb, segno, &se);
ec = be32_to_cpu(se.ec_level) >> 4;
ec++;
logfs_set_segment_erased(sb, segno, ec, 0);
logfs_write_ds(sb, ds, segno, ec);
err = super->s_devops->write_sb(sb, page);
page_cache_release(page);
return err;
}
int logfs_write_sb(struct super_block *sb)
{
struct logfs_super *super = logfs_super(sb);
int err;
/* First superblock */
err = write_one_sb(sb, super->s_devops->find_first_sb);
if (err)
return err;
/* Last superblock */
err = write_one_sb(sb, super->s_devops->find_last_sb);
if (err)
return err;
return 0;
}
static int ds_cmp(const void *ds0, const void *ds1)
{
size_t len = sizeof(struct logfs_disk_super);
/* We know the segment headers differ, so ignore them */
len -= LOGFS_SEGMENT_HEADERSIZE;
ds0 += LOGFS_SEGMENT_HEADERSIZE;
ds1 += LOGFS_SEGMENT_HEADERSIZE;
return memcmp(ds0, ds1, len);
}
static int logfs_recover_sb(struct super_block *sb)
{
struct logfs_super *super = logfs_super(sb);
struct logfs_disk_super _ds0, *ds0 = &_ds0;
struct logfs_disk_super _ds1, *ds1 = &_ds1;
int err, valid0, valid1;
/* read first superblock */
err = wbuf_read(sb, super->s_sb_ofs[0], sizeof(*ds0), ds0);
if (err)
return err;
/* read last superblock */
err = wbuf_read(sb, super->s_sb_ofs[1], sizeof(*ds1), ds1);
if (err)
return err;
valid0 = logfs_check_ds(ds0) == 0;
valid1 = logfs_check_ds(ds1) == 0;
if (!valid0 && valid1) {
printk(KERN_INFO"First superblock is invalid - fixing.\n");
return write_one_sb(sb, super->s_devops->find_first_sb);
}
if (valid0 && !valid1) {
printk(KERN_INFO"Last superblock is invalid - fixing.\n");
return write_one_sb(sb, super->s_devops->find_last_sb);
}
if (valid0 && valid1 && ds_cmp(ds0, ds1)) {
printk(KERN_INFO"Superblocks don't match - fixing.\n");
return logfs_write_sb(sb);
}
/* If neither is valid now, something's wrong. Didn't we properly
* check them before?!? */
BUG_ON(!valid0 && !valid1);
return 0;
}
static int logfs_make_writeable(struct super_block *sb)
{
int err;
err = logfs_open_segfile(sb);
if (err)
return err;
/* Repair any broken superblock copies */
err = logfs_recover_sb(sb);
if (err)
return err;
/* Check areas for trailing unaccounted data */
err = logfs_check_areas(sb);
if (err)
return err;
/* Do one GC pass before any data gets dirtied */
logfs_gc_pass(sb);
/* after all initializations are done, replay the journal
* for rw-mounts, if necessary */
err = logfs_replay_journal(sb);
if (err)
return err;
return 0;
}
static int logfs_get_sb_final(struct super_block *sb)
{
struct logfs_super *super = logfs_super(sb);
struct inode *rootdir;
int err;
/* root dir */
rootdir = logfs_iget(sb, LOGFS_INO_ROOT);
if (IS_ERR(rootdir))
goto fail;
sb->s_root = d_make_root(rootdir);
if (!sb->s_root)
goto fail;
/* at that point we know that ->put_super() will be called */
super->s_erase_page = alloc_pages(GFP_KERNEL, 0);
if (!super->s_erase_page)
return -ENOMEM;
memset(page_address(super->s_erase_page), 0xFF, PAGE_SIZE);
/* FIXME: check for read-only mounts */
err = logfs_make_writeable(sb);
if (err) {
__free_page(super->s_erase_page);
return err;
}
log_super("LogFS: Finished mounting\n");
return 0;
fail:
iput(super->s_master_inode);
iput(super->s_segfile_inode);
iput(super->s_mapping_inode);
return -EIO;
}
int logfs_check_ds(struct logfs_disk_super *ds)
{
struct logfs_segment_header *sh = &ds->ds_sh;
if (ds->ds_magic != cpu_to_be64(LOGFS_MAGIC))
return -EINVAL;
if (sh->crc != logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4))
return -EINVAL;
if (ds->ds_crc != logfs_crc32(ds, sizeof(*ds),
LOGFS_SEGMENT_HEADERSIZE + 12))
return -EINVAL;
return 0;
}
static struct page *find_super_block(struct super_block *sb)
{
struct logfs_super *super = logfs_super(sb);
struct page *first, *last;
first = super->s_devops->find_first_sb(sb, &super->s_sb_ofs[0]);
if (!first || IS_ERR(first))
return NULL;
last = super->s_devops->find_last_sb(sb, &super->s_sb_ofs[1]);
if (!last || IS_ERR(last)) {
page_cache_release(first);
return NULL;
}
if (!logfs_check_ds(page_address(first))) {
page_cache_release(last);
return first;
}
/* First one didn't work, try the second superblock */
if (!logfs_check_ds(page_address(last))) {
page_cache_release(first);
return last;
}
/* Neither worked, sorry folks */
page_cache_release(first);
page_cache_release(last);
return NULL;
}
static int __logfs_read_sb(struct super_block *sb)
{
struct logfs_super *super = logfs_super(sb);
struct page *page;
struct logfs_disk_super *ds;
int i;
page = find_super_block(sb);
if (!page)
return -EINVAL;
ds = page_address(page);
super->s_size = be64_to_cpu(ds->ds_filesystem_size);
super->s_root_reserve = be64_to_cpu(ds->ds_root_reserve);
super->s_speed_reserve = be64_to_cpu(ds->ds_speed_reserve);
super->s_bad_seg_reserve = be32_to_cpu(ds->ds_bad_seg_reserve);
super->s_segsize = 1 << ds->ds_segment_shift;
super->s_segmask = (1 << ds->ds_segment_shift) - 1;
super->s_segshift = ds->ds_segment_shift;
sb->s_blocksize = 1 << ds->ds_block_shift;
sb->s_blocksize_bits = ds->ds_block_shift;
super->s_writesize = 1 << ds->ds_write_shift;
super->s_writeshift = ds->ds_write_shift;
super->s_no_segs = super->s_size >> super->s_segshift;
super->s_no_blocks = super->s_segsize >> sb->s_blocksize_bits;
super->s_feature_incompat = be64_to_cpu(ds->ds_feature_incompat);
super->s_feature_ro_compat = be64_to_cpu(ds->ds_feature_ro_compat);
super->s_feature_compat = be64_to_cpu(ds->ds_feature_compat);
super->s_feature_flags = be64_to_cpu(ds->ds_feature_flags);
journal_for_each(i)
super->s_journal_seg[i] = be32_to_cpu(ds->ds_journal_seg[i]);
super->s_ifile_levels = ds->ds_ifile_levels;
super->s_iblock_levels = ds->ds_iblock_levels;
super->s_data_levels = ds->ds_data_levels;
super->s_total_levels = super->s_ifile_levels + super->s_iblock_levels
+ super->s_data_levels;
page_cache_release(page);
return 0;
}
static int logfs_read_sb(struct super_block *sb, int read_only)
{
struct logfs_super *super = logfs_super(sb);
int ret;
super->s_btree_pool = mempool_create(32, btree_alloc, btree_free, NULL);
if (!super->s_btree_pool)
return -ENOMEM;
btree_init_mempool64(&super->s_shadow_tree.new, super->s_btree_pool);
btree_init_mempool64(&super->s_shadow_tree.old, super->s_btree_pool);
btree_init_mempool32(&super->s_shadow_tree.segment_map,
super->s_btree_pool);
ret = logfs_init_mapping(sb);
if (ret)
return ret;
ret = __logfs_read_sb(sb);
if (ret)
return ret;
if (super->s_feature_incompat & ~LOGFS_FEATURES_INCOMPAT)
return -EIO;
if ((super->s_feature_ro_compat & ~LOGFS_FEATURES_RO_COMPAT) &&
!read_only)
return -EIO;
ret = logfs_init_rw(sb);
if (ret)
return ret;
ret = logfs_init_areas(sb);
if (ret)
return ret;
ret = logfs_init_gc(sb);
if (ret)
return ret;
ret = logfs_init_journal(sb);
if (ret)
return ret;
return 0;
}
static void logfs_kill_sb(struct super_block *sb)
{
struct logfs_super *super = logfs_super(sb);
log_super("LogFS: Start unmounting\n");
/* Alias entries slow down mount, so evict as many as possible */
sync_filesystem(sb);
logfs_write_anchor(sb);
free_areas(sb);
/*
* From this point on alias entries are simply dropped - and any
* writes to the object store are considered bugs.
*/
log_super("LogFS: Now in shutdown\n");
generic_shutdown_super(sb);
super->s_flags |= LOGFS_SB_FLAG_SHUTDOWN;
BUG_ON(super->s_dirty_used_bytes || super->s_dirty_free_bytes);
logfs_cleanup_gc(sb);
logfs_cleanup_journal(sb);
logfs_cleanup_areas(sb);
logfs_cleanup_rw(sb);
if (super->s_erase_page)
__free_page(super->s_erase_page);
super->s_devops->put_device(super);
logfs_mempool_destroy(super->s_btree_pool);
logfs_mempool_destroy(super->s_alias_pool);
kfree(super);
log_super("LogFS: Finished unmounting\n");
}
static struct dentry *logfs_get_sb_device(struct logfs_super *super,
struct file_system_type *type, int flags)
{
struct super_block *sb;
int err = -ENOMEM;
static int mount_count;
log_super("LogFS: Start mount %x\n", mount_count++);
err = -EINVAL;
sb = sget(type, logfs_sb_test, logfs_sb_set, flags | MS_NOATIME, super);
if (IS_ERR(sb)) {
super->s_devops->put_device(super);
kfree(super);
return ERR_CAST(sb);
}
if (sb->s_root) {
/* Device is already in use */
super->s_devops->put_device(super);
kfree(super);
return dget(sb->s_root);
}
/*
* sb->s_maxbytes is limited to 8TB. On 32bit systems, the page cache
* only covers 16TB and the upper 8TB are used for indirect blocks.
* On 64bit system we could bump up the limit, but that would make
* the filesystem incompatible with 32bit systems.
*/
sb->s_maxbytes = (1ull << 43) - 1;
sb->s_max_links = LOGFS_LINK_MAX;
sb->s_op = &logfs_super_operations;
err = logfs_read_sb(sb, sb->s_flags & MS_RDONLY);
if (err)
goto err1;
sb->s_flags |= MS_ACTIVE;
err = logfs_get_sb_final(sb);
if (err) {
deactivate_locked_super(sb);
return ERR_PTR(err);
}
return dget(sb->s_root);
err1:
/* no ->s_root, no ->put_super() */
iput(super->s_master_inode);
iput(super->s_segfile_inode);
iput(super->s_mapping_inode);
deactivate_locked_super(sb);
return ERR_PTR(err);
}
static struct dentry *logfs_mount(struct file_system_type *type, int flags,
const char *devname, void *data)
{
ulong mtdnr;
struct logfs_super *super;
int err;
super = kzalloc(sizeof(*super), GFP_KERNEL);
if (!super)
return ERR_PTR(-ENOMEM);
mutex_init(&super->s_dirop_mutex);
mutex_init(&super->s_object_alias_mutex);
INIT_LIST_HEAD(&super->s_freeing_list);
if (!devname)
err = logfs_get_sb_bdev(super, type, devname);
else if (strncmp(devname, "mtd", 3))
err = logfs_get_sb_bdev(super, type, devname);
else {
char *garbage;
mtdnr = simple_strtoul(devname+3, &garbage, 0);
if (*garbage)
err = -EINVAL;
else
err = logfs_get_sb_mtd(super, mtdnr);
}
if (err) {
kfree(super);
return ERR_PTR(err);
}
return logfs_get_sb_device(super, type, flags);
}
static struct file_system_type logfs_fs_type = {
.owner = THIS_MODULE,
.name = "logfs",
.mount = logfs_mount,
.kill_sb = logfs_kill_sb,
.fs_flags = FS_REQUIRES_DEV,
};
MODULE_ALIAS_FS("logfs");
static int __init logfs_init(void)
{
int ret;
emergency_page = alloc_pages(GFP_KERNEL, 0);
if (!emergency_page)
return -ENOMEM;
ret = logfs_compr_init();
if (ret)
goto out1;
ret = logfs_init_inode_cache();
if (ret)
goto out2;
ret = register_filesystem(&logfs_fs_type);
if (!ret)
return 0;
logfs_destroy_inode_cache();
out2:
logfs_compr_exit();
out1:
__free_pages(emergency_page, 0);
return ret;
}
static void __exit logfs_exit(void)
{
unregister_filesystem(&logfs_fs_type);
logfs_destroy_inode_cache();
logfs_compr_exit();
__free_pages(emergency_page, 0);
}
module_init(logfs_init);
module_exit(logfs_exit);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
MODULE_DESCRIPTION("scalable flash filesystem");
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