On 1/10/2017 9:28 AM, Stephen Smalley 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 <[email protected]> > Signed-off-by: Stephen Smalley <[email protected]>
Acked-by: Casey Schaufler <[email protected]> > --- > 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), _______________________________________________ Selinux mailing list [email protected] To unsubscribe, send email to [email protected]. 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