kernel-ark/security/commoncap.c
Alan Cox 34b4e4aa3c fix NULL pointer dereference in __vm_enough_memory()
The new exec code inserts an accounted vma into an mm struct which is not
current->mm.  The existing memory check code has a hard coded assumption
that this does not happen as does the security code.

As the correct mm is known we pass the mm to the security method and the
helper function.  A new security test is added for the case where we need
to pass the mm and the existing one is modified to pass current->mm to
avoid the need to change large amounts of code.

(Thanks to Tobias for fixing rejects and testing)

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: WU Fengguang <wfg@mail.ustc.edu.cn>
Cc: James Morris <jmorris@redhat.com>
Cc: Tobias Diedrich <ranma+kernel@tdiedrich.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-08-22 19:52:45 -07:00

345 lines
9.4 KiB
C

/* Common capabilities, needed by capability.o and root_plug.o
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
*/
#include <linux/capability.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/security.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
#include <linux/ptrace.h>
#include <linux/xattr.h>
#include <linux/hugetlb.h>
int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
{
NETLINK_CB(skb).eff_cap = current->cap_effective;
return 0;
}
EXPORT_SYMBOL(cap_netlink_send);
int cap_netlink_recv(struct sk_buff *skb, int cap)
{
if (!cap_raised(NETLINK_CB(skb).eff_cap, cap))
return -EPERM;
return 0;
}
EXPORT_SYMBOL(cap_netlink_recv);
int cap_capable (struct task_struct *tsk, int cap)
{
/* Derived from include/linux/sched.h:capable. */
if (cap_raised(tsk->cap_effective, cap))
return 0;
return -EPERM;
}
int cap_settime(struct timespec *ts, struct timezone *tz)
{
if (!capable(CAP_SYS_TIME))
return -EPERM;
return 0;
}
int cap_ptrace (struct task_struct *parent, struct task_struct *child)
{
/* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
if (!cap_issubset(child->cap_permitted, parent->cap_permitted) &&
!__capable(parent, CAP_SYS_PTRACE))
return -EPERM;
return 0;
}
int cap_capget (struct task_struct *target, kernel_cap_t *effective,
kernel_cap_t *inheritable, kernel_cap_t *permitted)
{
/* Derived from kernel/capability.c:sys_capget. */
*effective = cap_t (target->cap_effective);
*inheritable = cap_t (target->cap_inheritable);
*permitted = cap_t (target->cap_permitted);
return 0;
}
int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
kernel_cap_t *inheritable, kernel_cap_t *permitted)
{
/* Derived from kernel/capability.c:sys_capset. */
/* verify restrictions on target's new Inheritable set */
if (!cap_issubset (*inheritable,
cap_combine (target->cap_inheritable,
current->cap_permitted))) {
return -EPERM;
}
/* verify restrictions on target's new Permitted set */
if (!cap_issubset (*permitted,
cap_combine (target->cap_permitted,
current->cap_permitted))) {
return -EPERM;
}
/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
if (!cap_issubset (*effective, *permitted)) {
return -EPERM;
}
return 0;
}
void cap_capset_set (struct task_struct *target, kernel_cap_t *effective,
kernel_cap_t *inheritable, kernel_cap_t *permitted)
{
target->cap_effective = *effective;
target->cap_inheritable = *inheritable;
target->cap_permitted = *permitted;
}
int cap_bprm_set_security (struct linux_binprm *bprm)
{
/* Copied from fs/exec.c:prepare_binprm. */
/* We don't have VFS support for capabilities yet */
cap_clear (bprm->cap_inheritable);
cap_clear (bprm->cap_permitted);
cap_clear (bprm->cap_effective);
/* To support inheritance of root-permissions and suid-root
* executables under compatibility mode, we raise all three
* capability sets for the file.
*
* If only the real uid is 0, we only raise the inheritable
* and permitted sets of the executable file.
*/
if (!issecure (SECURE_NOROOT)) {
if (bprm->e_uid == 0 || current->uid == 0) {
cap_set_full (bprm->cap_inheritable);
cap_set_full (bprm->cap_permitted);
}
if (bprm->e_uid == 0)
cap_set_full (bprm->cap_effective);
}
return 0;
}
void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
{
/* Derived from fs/exec.c:compute_creds. */
kernel_cap_t new_permitted, working;
new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
working = cap_intersect (bprm->cap_inheritable,
current->cap_inheritable);
new_permitted = cap_combine (new_permitted, working);
if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
!cap_issubset (new_permitted, current->cap_permitted)) {
set_dumpable(current->mm, suid_dumpable);
if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
if (!capable(CAP_SETUID)) {
bprm->e_uid = current->uid;
bprm->e_gid = current->gid;
}
if (!capable (CAP_SETPCAP)) {
new_permitted = cap_intersect (new_permitted,
current->cap_permitted);
}
}
}
current->suid = current->euid = current->fsuid = bprm->e_uid;
current->sgid = current->egid = current->fsgid = bprm->e_gid;
/* For init, we want to retain the capabilities set
* in the init_task struct. Thus we skip the usual
* capability rules */
if (!is_init(current)) {
current->cap_permitted = new_permitted;
current->cap_effective =
cap_intersect (new_permitted, bprm->cap_effective);
}
/* AUD: Audit candidate if current->cap_effective is set */
current->keep_capabilities = 0;
}
int cap_bprm_secureexec (struct linux_binprm *bprm)
{
/* If/when this module is enhanced to incorporate capability
bits on files, the test below should be extended to also perform a
test between the old and new capability sets. For now,
it simply preserves the legacy decision algorithm used by
the old userland. */
return (current->euid != current->uid ||
current->egid != current->gid);
}
int cap_inode_setxattr(struct dentry *dentry, char *name, void *value,
size_t size, int flags)
{
if (!strncmp(name, XATTR_SECURITY_PREFIX,
sizeof(XATTR_SECURITY_PREFIX) - 1) &&
!capable(CAP_SYS_ADMIN))
return -EPERM;
return 0;
}
int cap_inode_removexattr(struct dentry *dentry, char *name)
{
if (!strncmp(name, XATTR_SECURITY_PREFIX,
sizeof(XATTR_SECURITY_PREFIX) - 1) &&
!capable(CAP_SYS_ADMIN))
return -EPERM;
return 0;
}
/* moved from kernel/sys.c. */
/*
* cap_emulate_setxuid() fixes the effective / permitted capabilities of
* a process after a call to setuid, setreuid, or setresuid.
*
* 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
* {r,e,s}uid != 0, the permitted and effective capabilities are
* cleared.
*
* 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
* capabilities of the process are cleared.
*
* 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
* capabilities are set to the permitted capabilities.
*
* fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
* never happen.
*
* -astor
*
* cevans - New behaviour, Oct '99
* A process may, via prctl(), elect to keep its capabilities when it
* calls setuid() and switches away from uid==0. Both permitted and
* effective sets will be retained.
* Without this change, it was impossible for a daemon to drop only some
* of its privilege. The call to setuid(!=0) would drop all privileges!
* Keeping uid 0 is not an option because uid 0 owns too many vital
* files..
* Thanks to Olaf Kirch and Peter Benie for spotting this.
*/
static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
int old_suid)
{
if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
(current->uid != 0 && current->euid != 0 && current->suid != 0) &&
!current->keep_capabilities) {
cap_clear (current->cap_permitted);
cap_clear (current->cap_effective);
}
if (old_euid == 0 && current->euid != 0) {
cap_clear (current->cap_effective);
}
if (old_euid != 0 && current->euid == 0) {
current->cap_effective = current->cap_permitted;
}
}
int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
int flags)
{
switch (flags) {
case LSM_SETID_RE:
case LSM_SETID_ID:
case LSM_SETID_RES:
/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
if (!issecure (SECURE_NO_SETUID_FIXUP)) {
cap_emulate_setxuid (old_ruid, old_euid, old_suid);
}
break;
case LSM_SETID_FS:
{
uid_t old_fsuid = old_ruid;
/* Copied from kernel/sys.c:setfsuid. */
/*
* FIXME - is fsuser used for all CAP_FS_MASK capabilities?
* if not, we might be a bit too harsh here.
*/
if (!issecure (SECURE_NO_SETUID_FIXUP)) {
if (old_fsuid == 0 && current->fsuid != 0) {
cap_t (current->cap_effective) &=
~CAP_FS_MASK;
}
if (old_fsuid != 0 && current->fsuid == 0) {
cap_t (current->cap_effective) |=
(cap_t (current->cap_permitted) &
CAP_FS_MASK);
}
}
break;
}
default:
return -EINVAL;
}
return 0;
}
void cap_task_reparent_to_init (struct task_struct *p)
{
p->cap_effective = CAP_INIT_EFF_SET;
p->cap_inheritable = CAP_INIT_INH_SET;
p->cap_permitted = CAP_FULL_SET;
p->keep_capabilities = 0;
return;
}
int cap_syslog (int type)
{
if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
return -EPERM;
return 0;
}
int cap_vm_enough_memory(struct mm_struct *mm, long pages)
{
int cap_sys_admin = 0;
if (cap_capable(current, CAP_SYS_ADMIN) == 0)
cap_sys_admin = 1;
return __vm_enough_memory(mm, pages, cap_sys_admin);
}
EXPORT_SYMBOL(cap_capable);
EXPORT_SYMBOL(cap_settime);
EXPORT_SYMBOL(cap_ptrace);
EXPORT_SYMBOL(cap_capget);
EXPORT_SYMBOL(cap_capset_check);
EXPORT_SYMBOL(cap_capset_set);
EXPORT_SYMBOL(cap_bprm_set_security);
EXPORT_SYMBOL(cap_bprm_apply_creds);
EXPORT_SYMBOL(cap_bprm_secureexec);
EXPORT_SYMBOL(cap_inode_setxattr);
EXPORT_SYMBOL(cap_inode_removexattr);
EXPORT_SYMBOL(cap_task_post_setuid);
EXPORT_SYMBOL(cap_task_reparent_to_init);
EXPORT_SYMBOL(cap_syslog);
EXPORT_SYMBOL(cap_vm_enough_memory);
MODULE_DESCRIPTION("Standard Linux Common Capabilities Security Module");
MODULE_LICENSE("GPL");