Commit 3a2f5a59 authored by Stephen Smalley's avatar Stephen Smalley Committed by Paul Moore
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security,selinux,smack: kill security_task_wait hook 



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: default avataryangshukui <yangshukui@huawei.com>
Signed-off-by: default avatarStephen Smalley <sds@tycho.nsa.gov>
Acked-by: default avatarCasey Schaufler <casey@schaufler-ca.com>
Acked-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
parent b4ba35c7

include/linux/lsm_hooks.h

+0 −7
Original line number Diff line number Diff line
@@ -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;

include/linux/security.h

+0 −6
Original line number Diff line number Diff line
@@ -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,

kernel/exit.c

+2 −17
Original line number Diff line number Diff line
@@ -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)

{

security/security.c

+0 −6
Original line number Diff line number Diff line
@@ -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),

security/selinux/hooks.c

+0 −7
Original line number Diff line number Diff line
@@ -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),

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