On 1/12/2017 8:03 AM, Paul Moore wrote:
> On Tue, Jan 10, 2017 at 12:28 PM, Stephen Smalley <sds@xxxxxxxxxxxxx> wrote:
>> 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>
Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
In case you miss my earlier Ack.
>> ---
>> 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(-)
> Looks good to me and I'm not seeing any objections so I'll go ahead
> and merge this into the selinux/next branch today unless Casey already
> merged this into the Smack tree - Casey?
Please go ahead and merge into the SELinux tree.
It makes sense to do this atomically.
Thank you.
>
>> 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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