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![Eric W. Biederman](/assets/img/avatar_default.png)
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>
441 lines
10 KiB
C
441 lines
10 KiB
C
/*
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* JFFS2 -- Journalling Flash File System, Version 2.
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*
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* Copyright © 2001-2007 Red Hat, Inc.
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*
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* Created by David Woodhouse <dwmw2@infradead.org>
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*
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* For licensing information, see the file 'LICENCE' in this directory.
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*
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/list.h>
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#include <linux/fs.h>
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#include <linux/err.h>
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#include <linux/mount.h>
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#include <linux/parser.h>
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#include <linux/jffs2.h>
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#include <linux/pagemap.h>
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#include <linux/mtd/super.h>
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#include <linux/ctype.h>
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#include <linux/namei.h>
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#include <linux/seq_file.h>
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#include <linux/exportfs.h>
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#include "compr.h"
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#include "nodelist.h"
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static void jffs2_put_super(struct super_block *);
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static struct kmem_cache *jffs2_inode_cachep;
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static struct inode *jffs2_alloc_inode(struct super_block *sb)
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{
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struct jffs2_inode_info *f;
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f = kmem_cache_alloc(jffs2_inode_cachep, GFP_KERNEL);
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if (!f)
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return NULL;
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return &f->vfs_inode;
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}
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static void jffs2_i_callback(struct rcu_head *head)
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{
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struct inode *inode = container_of(head, struct inode, i_rcu);
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kmem_cache_free(jffs2_inode_cachep, JFFS2_INODE_INFO(inode));
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}
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static void jffs2_destroy_inode(struct inode *inode)
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{
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call_rcu(&inode->i_rcu, jffs2_i_callback);
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}
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static void jffs2_i_init_once(void *foo)
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{
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struct jffs2_inode_info *f = foo;
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mutex_init(&f->sem);
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inode_init_once(&f->vfs_inode);
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}
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static const char *jffs2_compr_name(unsigned int compr)
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{
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switch (compr) {
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case JFFS2_COMPR_MODE_NONE:
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return "none";
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#ifdef CONFIG_JFFS2_LZO
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case JFFS2_COMPR_MODE_FORCELZO:
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return "lzo";
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#endif
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#ifdef CONFIG_JFFS2_ZLIB
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case JFFS2_COMPR_MODE_FORCEZLIB:
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return "zlib";
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#endif
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default:
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/* should never happen; programmer error */
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WARN_ON(1);
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return "";
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}
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}
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static int jffs2_show_options(struct seq_file *s, struct dentry *root)
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{
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struct jffs2_sb_info *c = JFFS2_SB_INFO(root->d_sb);
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struct jffs2_mount_opts *opts = &c->mount_opts;
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if (opts->override_compr)
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seq_printf(s, ",compr=%s", jffs2_compr_name(opts->compr));
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if (opts->rp_size)
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seq_printf(s, ",rp_size=%u", opts->rp_size / 1024);
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return 0;
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}
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static int jffs2_sync_fs(struct super_block *sb, int wait)
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{
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struct jffs2_sb_info *c = JFFS2_SB_INFO(sb);
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#ifdef CONFIG_JFFS2_FS_WRITEBUFFER
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cancel_delayed_work_sync(&c->wbuf_dwork);
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#endif
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mutex_lock(&c->alloc_sem);
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jffs2_flush_wbuf_pad(c);
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mutex_unlock(&c->alloc_sem);
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return 0;
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}
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static struct inode *jffs2_nfs_get_inode(struct super_block *sb, uint64_t ino,
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uint32_t generation)
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{
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/* We don't care about i_generation. We'll destroy the flash
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before we start re-using inode numbers anyway. And even
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if that wasn't true, we'd have other problems...*/
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return jffs2_iget(sb, ino);
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}
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static struct dentry *jffs2_fh_to_dentry(struct super_block *sb, struct fid *fid,
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int fh_len, int fh_type)
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{
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return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
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jffs2_nfs_get_inode);
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}
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static struct dentry *jffs2_fh_to_parent(struct super_block *sb, struct fid *fid,
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int fh_len, int fh_type)
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{
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return generic_fh_to_parent(sb, fid, fh_len, fh_type,
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jffs2_nfs_get_inode);
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}
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static struct dentry *jffs2_get_parent(struct dentry *child)
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{
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struct jffs2_inode_info *f;
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uint32_t pino;
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BUG_ON(!S_ISDIR(child->d_inode->i_mode));
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f = JFFS2_INODE_INFO(child->d_inode);
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pino = f->inocache->pino_nlink;
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JFFS2_DEBUG("Parent of directory ino #%u is #%u\n",
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f->inocache->ino, pino);
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return d_obtain_alias(jffs2_iget(child->d_inode->i_sb, pino));
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}
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static const struct export_operations jffs2_export_ops = {
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.get_parent = jffs2_get_parent,
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.fh_to_dentry = jffs2_fh_to_dentry,
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.fh_to_parent = jffs2_fh_to_parent,
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};
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/*
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* JFFS2 mount options.
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*
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* Opt_override_compr: override default compressor
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* Opt_rp_size: size of reserved pool in KiB
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* Opt_err: just end of array marker
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*/
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enum {
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Opt_override_compr,
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Opt_rp_size,
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Opt_err,
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};
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static const match_table_t tokens = {
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{Opt_override_compr, "compr=%s"},
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{Opt_rp_size, "rp_size=%u"},
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{Opt_err, NULL},
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};
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static int jffs2_parse_options(struct jffs2_sb_info *c, char *data)
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{
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substring_t args[MAX_OPT_ARGS];
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char *p, *name;
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unsigned int opt;
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if (!data)
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return 0;
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while ((p = strsep(&data, ","))) {
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int token;
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if (!*p)
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continue;
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token = match_token(p, tokens, args);
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switch (token) {
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case Opt_override_compr:
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name = match_strdup(&args[0]);
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if (!name)
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return -ENOMEM;
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if (!strcmp(name, "none"))
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c->mount_opts.compr = JFFS2_COMPR_MODE_NONE;
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#ifdef CONFIG_JFFS2_LZO
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else if (!strcmp(name, "lzo"))
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c->mount_opts.compr = JFFS2_COMPR_MODE_FORCELZO;
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#endif
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#ifdef CONFIG_JFFS2_ZLIB
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else if (!strcmp(name, "zlib"))
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c->mount_opts.compr =
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JFFS2_COMPR_MODE_FORCEZLIB;
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#endif
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else {
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pr_err("Error: unknown compressor \"%s\"\n",
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name);
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kfree(name);
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return -EINVAL;
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}
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kfree(name);
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c->mount_opts.override_compr = true;
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break;
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case Opt_rp_size:
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if (match_int(&args[0], &opt))
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return -EINVAL;
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opt *= 1024;
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if (opt > c->mtd->size) {
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pr_warn("Too large reserve pool specified, max "
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"is %llu KB\n", c->mtd->size / 1024);
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return -EINVAL;
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}
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c->mount_opts.rp_size = opt;
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break;
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default:
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pr_err("Error: unrecognized mount option '%s' or missing value\n",
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p);
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return -EINVAL;
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}
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}
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return 0;
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}
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static int jffs2_remount_fs(struct super_block *sb, int *flags, char *data)
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{
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struct jffs2_sb_info *c = JFFS2_SB_INFO(sb);
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int err;
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err = jffs2_parse_options(c, data);
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if (err)
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return -EINVAL;
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return jffs2_do_remount_fs(sb, flags, data);
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}
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static const struct super_operations jffs2_super_operations =
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{
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.alloc_inode = jffs2_alloc_inode,
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.destroy_inode =jffs2_destroy_inode,
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.put_super = jffs2_put_super,
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.statfs = jffs2_statfs,
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.remount_fs = jffs2_remount_fs,
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.evict_inode = jffs2_evict_inode,
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.dirty_inode = jffs2_dirty_inode,
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.show_options = jffs2_show_options,
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.sync_fs = jffs2_sync_fs,
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};
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/*
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* fill in the superblock
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*/
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static int jffs2_fill_super(struct super_block *sb, void *data, int silent)
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{
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struct jffs2_sb_info *c;
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int ret;
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jffs2_dbg(1, "jffs2_get_sb_mtd():"
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" New superblock for device %d (\"%s\")\n",
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sb->s_mtd->index, sb->s_mtd->name);
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c = kzalloc(sizeof(*c), GFP_KERNEL);
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if (!c)
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return -ENOMEM;
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c->mtd = sb->s_mtd;
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c->os_priv = sb;
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sb->s_fs_info = c;
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ret = jffs2_parse_options(c, data);
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if (ret) {
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kfree(c);
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return -EINVAL;
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}
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/* Initialize JFFS2 superblock locks, the further initialization will
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* be done later */
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mutex_init(&c->alloc_sem);
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mutex_init(&c->erase_free_sem);
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init_waitqueue_head(&c->erase_wait);
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init_waitqueue_head(&c->inocache_wq);
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spin_lock_init(&c->erase_completion_lock);
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spin_lock_init(&c->inocache_lock);
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sb->s_op = &jffs2_super_operations;
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sb->s_export_op = &jffs2_export_ops;
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sb->s_flags = sb->s_flags | MS_NOATIME;
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sb->s_xattr = jffs2_xattr_handlers;
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#ifdef CONFIG_JFFS2_FS_POSIX_ACL
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sb->s_flags |= MS_POSIXACL;
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#endif
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ret = jffs2_do_fill_super(sb, data, silent);
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return ret;
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}
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static struct dentry *jffs2_mount(struct file_system_type *fs_type,
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int flags, const char *dev_name,
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void *data)
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{
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return mount_mtd(fs_type, flags, dev_name, data, jffs2_fill_super);
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}
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static void jffs2_put_super (struct super_block *sb)
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{
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struct jffs2_sb_info *c = JFFS2_SB_INFO(sb);
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jffs2_dbg(2, "%s()\n", __func__);
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mutex_lock(&c->alloc_sem);
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jffs2_flush_wbuf_pad(c);
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mutex_unlock(&c->alloc_sem);
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jffs2_sum_exit(c);
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jffs2_free_ino_caches(c);
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jffs2_free_raw_node_refs(c);
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if (jffs2_blocks_use_vmalloc(c))
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vfree(c->blocks);
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else
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kfree(c->blocks);
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jffs2_flash_cleanup(c);
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kfree(c->inocache_list);
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jffs2_clear_xattr_subsystem(c);
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mtd_sync(c->mtd);
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jffs2_dbg(1, "%s(): returning\n", __func__);
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}
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static void jffs2_kill_sb(struct super_block *sb)
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{
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struct jffs2_sb_info *c = JFFS2_SB_INFO(sb);
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if (!(sb->s_flags & MS_RDONLY))
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jffs2_stop_garbage_collect_thread(c);
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kill_mtd_super(sb);
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kfree(c);
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}
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static struct file_system_type jffs2_fs_type = {
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.owner = THIS_MODULE,
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.name = "jffs2",
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.mount = jffs2_mount,
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.kill_sb = jffs2_kill_sb,
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};
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MODULE_ALIAS_FS("jffs2");
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static int __init init_jffs2_fs(void)
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{
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int ret;
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/* Paranoia checks for on-medium structures. If we ask GCC
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to pack them with __attribute__((packed)) then it _also_
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assumes that they're not aligned -- so it emits crappy
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code on some architectures. Ideally we want an attribute
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which means just 'no padding', without the alignment
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thing. But GCC doesn't have that -- we have to just
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hope the structs are the right sizes, instead. */
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BUILD_BUG_ON(sizeof(struct jffs2_unknown_node) != 12);
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BUILD_BUG_ON(sizeof(struct jffs2_raw_dirent) != 40);
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BUILD_BUG_ON(sizeof(struct jffs2_raw_inode) != 68);
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BUILD_BUG_ON(sizeof(struct jffs2_raw_summary) != 32);
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pr_info("version 2.2."
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#ifdef CONFIG_JFFS2_FS_WRITEBUFFER
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" (NAND)"
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#endif
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#ifdef CONFIG_JFFS2_SUMMARY
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" (SUMMARY) "
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#endif
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" © 2001-2006 Red Hat, Inc.\n");
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jffs2_inode_cachep = kmem_cache_create("jffs2_i",
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sizeof(struct jffs2_inode_info),
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0, (SLAB_RECLAIM_ACCOUNT|
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SLAB_MEM_SPREAD),
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jffs2_i_init_once);
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if (!jffs2_inode_cachep) {
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pr_err("error: Failed to initialise inode cache\n");
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return -ENOMEM;
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}
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ret = jffs2_compressors_init();
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if (ret) {
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pr_err("error: Failed to initialise compressors\n");
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goto out;
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}
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ret = jffs2_create_slab_caches();
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if (ret) {
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pr_err("error: Failed to initialise slab caches\n");
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goto out_compressors;
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}
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ret = register_filesystem(&jffs2_fs_type);
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if (ret) {
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pr_err("error: Failed to register filesystem\n");
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goto out_slab;
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}
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return 0;
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out_slab:
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jffs2_destroy_slab_caches();
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out_compressors:
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jffs2_compressors_exit();
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out:
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kmem_cache_destroy(jffs2_inode_cachep);
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return ret;
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}
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static void __exit exit_jffs2_fs(void)
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{
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unregister_filesystem(&jffs2_fs_type);
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jffs2_destroy_slab_caches();
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jffs2_compressors_exit();
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/*
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* Make sure all delayed rcu free inodes are flushed before we
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* destroy cache.
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*/
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rcu_barrier();
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kmem_cache_destroy(jffs2_inode_cachep);
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}
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module_init(init_jffs2_fs);
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module_exit(exit_jffs2_fs);
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MODULE_DESCRIPTION("The Journalling Flash File System, v2");
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MODULE_AUTHOR("Red Hat, Inc.");
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MODULE_LICENSE("GPL"); // Actually dual-licensed, but it doesn't matter for
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// the sake of this tag. It's Free Software.
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