linux-stable/kernel/bpf/inode.c
Alexei Starovoitov 92117d8443 bpf: fix refcnt overflow
On a system with >32Gbyte of phyiscal memory and infinite RLIMIT_MEMLOCK,
the malicious application may overflow 32-bit bpf program refcnt.
It's also possible to overflow map refcnt on 1Tb system.
Impose 32k hard limit which means that the same bpf program or
map cannot be shared by more than 32k processes.

Fixes: 1be7f75d16 ("bpf: enable non-root eBPF programs")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-04-28 17:29:45 -04:00

408 lines
7.9 KiB
C

/*
* Minimal file system backend for holding eBPF maps and programs,
* used by bpf(2) object pinning.
*
* Authors:
*
* Daniel Borkmann <daniel@iogearbox.net>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* version 2 as published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/magic.h>
#include <linux/major.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/fs.h>
#include <linux/kdev_t.h>
#include <linux/filter.h>
#include <linux/bpf.h>
enum bpf_type {
BPF_TYPE_UNSPEC = 0,
BPF_TYPE_PROG,
BPF_TYPE_MAP,
};
static void *bpf_any_get(void *raw, enum bpf_type type)
{
switch (type) {
case BPF_TYPE_PROG:
raw = bpf_prog_inc(raw);
break;
case BPF_TYPE_MAP:
raw = bpf_map_inc(raw, true);
break;
default:
WARN_ON_ONCE(1);
break;
}
return raw;
}
static void bpf_any_put(void *raw, enum bpf_type type)
{
switch (type) {
case BPF_TYPE_PROG:
bpf_prog_put(raw);
break;
case BPF_TYPE_MAP:
bpf_map_put_with_uref(raw);
break;
default:
WARN_ON_ONCE(1);
break;
}
}
static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type)
{
void *raw;
*type = BPF_TYPE_MAP;
raw = bpf_map_get_with_uref(ufd);
if (IS_ERR(raw)) {
*type = BPF_TYPE_PROG;
raw = bpf_prog_get(ufd);
}
return raw;
}
static const struct inode_operations bpf_dir_iops;
static const struct inode_operations bpf_prog_iops = { };
static const struct inode_operations bpf_map_iops = { };
static struct inode *bpf_get_inode(struct super_block *sb,
const struct inode *dir,
umode_t mode)
{
struct inode *inode;
switch (mode & S_IFMT) {
case S_IFDIR:
case S_IFREG:
break;
default:
return ERR_PTR(-EINVAL);
}
inode = new_inode(sb);
if (!inode)
return ERR_PTR(-ENOSPC);
inode->i_ino = get_next_ino();
inode->i_atime = CURRENT_TIME;
inode->i_mtime = inode->i_atime;
inode->i_ctime = inode->i_atime;
inode_init_owner(inode, dir, mode);
return inode;
}
static int bpf_inode_type(const struct inode *inode, enum bpf_type *type)
{
*type = BPF_TYPE_UNSPEC;
if (inode->i_op == &bpf_prog_iops)
*type = BPF_TYPE_PROG;
else if (inode->i_op == &bpf_map_iops)
*type = BPF_TYPE_MAP;
else
return -EACCES;
return 0;
}
static bool bpf_dname_reserved(const struct dentry *dentry)
{
return strchr(dentry->d_name.name, '.');
}
static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
struct inode *inode;
if (bpf_dname_reserved(dentry))
return -EPERM;
inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR);
if (IS_ERR(inode))
return PTR_ERR(inode);
inode->i_op = &bpf_dir_iops;
inode->i_fop = &simple_dir_operations;
inc_nlink(inode);
inc_nlink(dir);
d_instantiate(dentry, inode);
dget(dentry);
return 0;
}
static int bpf_mkobj_ops(struct inode *dir, struct dentry *dentry,
umode_t mode, const struct inode_operations *iops)
{
struct inode *inode;
if (bpf_dname_reserved(dentry))
return -EPERM;
inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFREG);
if (IS_ERR(inode))
return PTR_ERR(inode);
inode->i_op = iops;
inode->i_private = dentry->d_fsdata;
d_instantiate(dentry, inode);
dget(dentry);
return 0;
}
static int bpf_mkobj(struct inode *dir, struct dentry *dentry, umode_t mode,
dev_t devt)
{
enum bpf_type type = MINOR(devt);
if (MAJOR(devt) != UNNAMED_MAJOR || !S_ISREG(mode) ||
dentry->d_fsdata == NULL)
return -EPERM;
switch (type) {
case BPF_TYPE_PROG:
return bpf_mkobj_ops(dir, dentry, mode, &bpf_prog_iops);
case BPF_TYPE_MAP:
return bpf_mkobj_ops(dir, dentry, mode, &bpf_map_iops);
default:
return -EPERM;
}
}
static int bpf_link(struct dentry *old_dentry, struct inode *dir,
struct dentry *new_dentry)
{
if (bpf_dname_reserved(new_dentry))
return -EPERM;
return simple_link(old_dentry, dir, new_dentry);
}
static int bpf_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
if (bpf_dname_reserved(new_dentry))
return -EPERM;
return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
}
static const struct inode_operations bpf_dir_iops = {
.lookup = simple_lookup,
.mknod = bpf_mkobj,
.mkdir = bpf_mkdir,
.rmdir = simple_rmdir,
.rename = bpf_rename,
.link = bpf_link,
.unlink = simple_unlink,
};
static int bpf_obj_do_pin(const struct filename *pathname, void *raw,
enum bpf_type type)
{
struct dentry *dentry;
struct inode *dir;
struct path path;
umode_t mode;
dev_t devt;
int ret;
dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());
devt = MKDEV(UNNAMED_MAJOR, type);
ret = security_path_mknod(&path, dentry, mode, devt);
if (ret)
goto out;
dir = d_inode(path.dentry);
if (dir->i_op != &bpf_dir_iops) {
ret = -EPERM;
goto out;
}
dentry->d_fsdata = raw;
ret = vfs_mknod(dir, dentry, mode, devt);
dentry->d_fsdata = NULL;
out:
done_path_create(&path, dentry);
return ret;
}
int bpf_obj_pin_user(u32 ufd, const char __user *pathname)
{
struct filename *pname;
enum bpf_type type;
void *raw;
int ret;
pname = getname(pathname);
if (IS_ERR(pname))
return PTR_ERR(pname);
raw = bpf_fd_probe_obj(ufd, &type);
if (IS_ERR(raw)) {
ret = PTR_ERR(raw);
goto out;
}
ret = bpf_obj_do_pin(pname, raw, type);
if (ret != 0)
bpf_any_put(raw, type);
out:
putname(pname);
return ret;
}
static void *bpf_obj_do_get(const struct filename *pathname,
enum bpf_type *type)
{
struct inode *inode;
struct path path;
void *raw;
int ret;
ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path);
if (ret)
return ERR_PTR(ret);
inode = d_backing_inode(path.dentry);
ret = inode_permission(inode, MAY_WRITE);
if (ret)
goto out;
ret = bpf_inode_type(inode, type);
if (ret)
goto out;
raw = bpf_any_get(inode->i_private, *type);
if (!IS_ERR(raw))
touch_atime(&path);
path_put(&path);
return raw;
out:
path_put(&path);
return ERR_PTR(ret);
}
int bpf_obj_get_user(const char __user *pathname)
{
enum bpf_type type = BPF_TYPE_UNSPEC;
struct filename *pname;
int ret = -ENOENT;
void *raw;
pname = getname(pathname);
if (IS_ERR(pname))
return PTR_ERR(pname);
raw = bpf_obj_do_get(pname, &type);
if (IS_ERR(raw)) {
ret = PTR_ERR(raw);
goto out;
}
if (type == BPF_TYPE_PROG)
ret = bpf_prog_new_fd(raw);
else if (type == BPF_TYPE_MAP)
ret = bpf_map_new_fd(raw);
else
goto out;
if (ret < 0)
bpf_any_put(raw, type);
out:
putname(pname);
return ret;
}
static void bpf_evict_inode(struct inode *inode)
{
enum bpf_type type;
truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
if (!bpf_inode_type(inode, &type))
bpf_any_put(inode->i_private, type);
}
static const struct super_operations bpf_super_ops = {
.statfs = simple_statfs,
.drop_inode = generic_delete_inode,
.evict_inode = bpf_evict_inode,
};
static int bpf_fill_super(struct super_block *sb, void *data, int silent)
{
static struct tree_descr bpf_rfiles[] = { { "" } };
struct inode *inode;
int ret;
ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles);
if (ret)
return ret;
sb->s_op = &bpf_super_ops;
inode = sb->s_root->d_inode;
inode->i_op = &bpf_dir_iops;
inode->i_mode &= ~S_IALLUGO;
inode->i_mode |= S_ISVTX | S_IRWXUGO;
return 0;
}
static struct dentry *bpf_mount(struct file_system_type *type, int flags,
const char *dev_name, void *data)
{
return mount_ns(type, flags, current->nsproxy->mnt_ns, bpf_fill_super);
}
static struct file_system_type bpf_fs_type = {
.owner = THIS_MODULE,
.name = "bpf",
.mount = bpf_mount,
.kill_sb = kill_litter_super,
.fs_flags = FS_USERNS_MOUNT,
};
MODULE_ALIAS_FS("bpf");
static int __init bpf_init(void)
{
int ret;
ret = sysfs_create_mount_point(fs_kobj, "bpf");
if (ret)
return ret;
ret = register_filesystem(&bpf_fs_type);
if (ret)
sysfs_remove_mount_point(fs_kobj, "bpf");
return ret;
}
fs_initcall(bpf_init);