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@xxxxxxxxxx>
Signed-off-by: Stephen Smalley <sds@xxxxxxxxxxxxx>
---
include/linux/lsm_hooks.h | 7 -------
include/linux/security.h | 6 ------
kernel/exit.c | 19 ++-----------------
security/security.c | 6 ------
security/selinux/hooks.c | 7 -------
security/smack/smack_lsm.c | 20 --------------------
6 files changed, 2 insertions(+), 63 deletions(-)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 0dde959..6fe7a5c 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -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;
diff --git a/include/linux/security.h b/include/linux/security.h
index f4ebac1..d3868f2 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -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,
diff --git a/kernel/exit.c b/kernel/exit.c
index 8f14b86..60f2451 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -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)
{
diff --git a/security/security.c b/security/security.c
index 32052f5..8c9fee5 100644
--- a/security/security.c
+++ b/security/security.c
@@ -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),
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index bada3cd..720dbd0 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3969,12 +3969,6 @@ 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)
{
@@ -6217,7 +6211,6 @@ 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),
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 8da4a6b..2166373 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -2272,25 +2272,6 @@ static int smack_task_kill(struct task_struct *p, struct siginfo *info,
}
/**
- * 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
* @inode: inode to copy to
@@ -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),
--
2.7.4
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