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security,selinux,smack: kill security_task_wait hook

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As reported by yangshukui, a permission denial from security_task_wait()
can lead to a soft lockup in zap_pid_ns_processes() since it only expects
sys_wait4() to return 0 or -ECHILD. Further, security_task_wait() can
in general lead to zombies; in the absence of some way to automatically
reparent a child process upon a denial, the hook is not useful.  Remove
the security hook and its implementations in SELinux and Smack.  Smack
already removed its check from its hook.

Reported-by: yangshukui <yangshukui@huawei.com>
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Stephen Smalley 2017-01-10 12:28:32 -05:00 committed by Paul Moore
parent b4ba35c75a
commit 3a2f5a59a6
6 changed files with 2 additions and 63 deletions
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7
include/linux/lsm_hooks.h
View File

@ -666,11 +666,6 @@
* @sig contains the signal value.
* @secid contains the sid of the process where the signal originated
* Return 0 if permission is granted.
* @task_wait:
* Check permission before allowing a process to reap a child process @p
* and collect its status information.
* @p contains the task_struct for process.
* Return 0 if permission is granted.
* @task_prctl:
* Check permission before performing a process control operation on the
* current process.
@ -1507,7 +1502,6 @@ union security_list_options {
int (*task_movememory)(struct task_struct *p);
int (*task_kill)(struct task_struct *p, struct siginfo *info,
int sig, u32 secid);
int (*task_wait)(struct task_struct *p);
int (*task_prctl)(int option, unsigned long arg2, unsigned long arg3,
unsigned long arg4, unsigned long arg5);
void (*task_to_inode)(struct task_struct *p, struct inode *inode);
@ -1767,7 +1761,6 @@ struct security_hook_heads {
struct list_head task_getscheduler;
struct list_head task_movememory;
struct list_head task_kill;
struct list_head task_wait;
struct list_head task_prctl;
struct list_head task_to_inode;
struct list_head ipc_permission;

6
include/linux/security.h
View File

@ -332,7 +332,6 @@ int security_task_getscheduler(struct task_struct *p);
int security_task_movememory(struct task_struct *p);
int security_task_kill(struct task_struct *p, struct siginfo *info,
int sig, u32 secid);
int security_task_wait(struct task_struct *p);
int security_task_prctl(int option, unsigned long arg2, unsigned long arg3,
unsigned long arg4, unsigned long arg5);
void security_task_to_inode(struct task_struct *p, struct inode *inode);
@ -980,11 +979,6 @@ static inline int security_task_kill(struct task_struct *p,
return 0;
}
static inline int security_task_wait(struct task_struct *p)
{
return 0;
}
static inline int security_task_prctl(int option, unsigned long arg2,
unsigned long arg3,
unsigned long arg4,

19
kernel/exit.c
View File

@ -14,7 +14,6 @@
#include <linux/tty.h>
#include <linux/iocontext.h>
#include <linux/key.h>
#include <linux/security.h>
#include <linux/cpu.h>
#include <linux/acct.h>
#include <linux/tsacct_kern.h>
@ -1360,7 +1359,7 @@ static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
* Returns nonzero for a final return, when we have unlocked tasklist_lock.
* Returns zero if the search for a child should continue;
* then ->notask_error is 0 if @p is an eligible child,
* or another error from security_task_wait(), or still -ECHILD.
* or still -ECHILD.
*/
static int wait_consider_task(struct wait_opts *wo, int ptrace,
struct task_struct *p)
@ -1380,20 +1379,6 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
if (!ret)
return ret;
ret = security_task_wait(p);
if (unlikely(ret < 0)) {
/*
* If we have not yet seen any eligible child,
* then let this error code replace -ECHILD.
* A permission error will give the user a clue
* to look for security policy problems, rather
* than for mysterious wait bugs.
*/
if (wo->notask_error)
wo->notask_error = ret;
return 0;
}
if (unlikely(exit_state == EXIT_TRACE)) {
/*
* ptrace == 0 means we are the natural parent. In this case
@ -1486,7 +1471,7 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
* Returns nonzero for a final return, when we have unlocked tasklist_lock.
* Returns zero if the search for a child should continue; then
* ->notask_error is 0 if there were any eligible children,
* or another error from security_task_wait(), or still -ECHILD.
* or still -ECHILD.
*/
static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
{

6
security/security.c
View File

@ -1025,11 +1025,6 @@ int security_task_kill(struct task_struct *p, struct siginfo *info,
return call_int_hook(task_kill, 0, p, info, sig, secid);
}
int security_task_wait(struct task_struct *p)
{
return call_int_hook(task_wait, 0, p);
}
int security_task_prctl(int option, unsigned long arg2, unsigned long arg3,
unsigned long arg4, unsigned long arg5)
{
@ -1769,7 +1764,6 @@ struct security_hook_heads security_hook_heads = {
.task_movememory =
LIST_HEAD_INIT(security_hook_heads.task_movememory),
.task_kill = LIST_HEAD_INIT(security_hook_heads.task_kill),
.task_wait = LIST_HEAD_INIT(security_hook_heads.task_wait),
.task_prctl = LIST_HEAD_INIT(security_hook_heads.task_prctl),
.task_to_inode =
LIST_HEAD_INIT(security_hook_heads.task_to_inode),

7
security/selinux/hooks.c
View File

@ -3963,12 +3963,6 @@ static int selinux_task_kill(struct task_struct *p, struct siginfo *info,
return avc_has_perm(secid, task_sid(p), SECCLASS_PROCESS, perm, NULL);
}
static int selinux_task_wait(struct task_struct *p)
{
return avc_has_perm(task_sid(p), current_sid(), SECCLASS_PROCESS,
PROCESS__SIGCHLD, NULL);
}
static void selinux_task_to_inode(struct task_struct *p,
struct inode *inode)
{
@ -6211,7 +6205,6 @@ static struct security_hook_list selinux_hooks[] = {
LSM_HOOK_INIT(task_getscheduler, selinux_task_getscheduler),
LSM_HOOK_INIT(task_movememory, selinux_task_movememory),
LSM_HOOK_INIT(task_kill, selinux_task_kill),
LSM_HOOK_INIT(task_wait, selinux_task_wait),
LSM_HOOK_INIT(task_to_inode, selinux_task_to_inode),
LSM_HOOK_INIT(ipc_permission, selinux_ipc_permission),

20
security/smack/smack_lsm.c
View File

@ -2271,25 +2271,6 @@ static int smack_task_kill(struct task_struct *p, struct siginfo *info,
return rc;
}
/**
* smack_task_wait - Smack access check for waiting
* @p: task to wait for
*
* Returns 0
*/
static int smack_task_wait(struct task_struct *p)
{
/*
* Allow the operation to succeed.
* Zombies are bad.
* In userless environments (e.g. phones) programs
* get marked with SMACK64EXEC and even if the parent
* and child shouldn't be talking the parent still
* may expect to know when the child exits.
*/
return 0;
}
/**
* smack_task_to_inode - copy task smack into the inode blob
* @p: task to copy from
@ -4658,7 +4639,6 @@ static struct security_hook_list smack_hooks[] = {
LSM_HOOK_INIT(task_getscheduler, smack_task_getscheduler),
LSM_HOOK_INIT(task_movememory, smack_task_movememory),
LSM_HOOK_INIT(task_kill, smack_task_kill),
LSM_HOOK_INIT(task_wait, smack_task_wait),
LSM_HOOK_INIT(task_to_inode, smack_task_to_inode),
LSM_HOOK_INIT(ipc_permission, smack_ipc_permission),