1 files changed, 145 insertions, 56 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 4e3cff10fdce..7165af5f1b11 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -226,7 +226,7 @@ static inline void print_dropped_signal(int sig)
 /*
  * allocate a new signal queue record
  * - this may be called without locks if and only if t == current, otherwise an
- *   appopriate lock must be held to stop the target task from exiting
+ *   appropriate lock must be held to stop the target task from exiting
  */
 static struct sigqueue *
 __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit)
@@ -375,15 +375,15 @@ int unhandled_signal(struct task_struct *tsk, int sig)
         return !tracehook_consider_fatal_signal(tsk, sig);
 }
 
-
-/* Notify the system that a driver wants to block all signals for this
+/*
+ * Notify the system that a driver wants to block all signals for this
  * process, and wants to be notified if any signals at all were to be
  * sent/acted upon.  If the notifier routine returns non-zero, then the
  * signal will be acted upon after all.  If the notifier routine returns 0,
  * then then signal will be blocked.  Only one block per process is
  * allowed.  priv is a pointer to private data that the notifier routine
- * can use to determine if the signal should be blocked or not.  */
-
+ * can use to determine if the signal should be blocked or not.
+ */
 void
 block_all_signals(int (*notifier)(void *priv), void *priv, sigset_t *mask)
 {
@@ -434,9 +434,10 @@ still_pending:
                 copy_siginfo(info, &first->info);
                 __sigqueue_free(first);
         } else {
-                /* Ok, it wasn't in the queue.  This must be
-                   a fast-pathed signal or we must have been
-                   out of queue space.  So zero out the info.
+                /*
+                 * Ok, it wasn't in the queue.  This must be
+                 * a fast-pathed signal or we must have been
+                 * out of queue space.  So zero out the info.
                  */
                 info->si_signo = sig;
                 info->si_errno = 0;
@@ -468,7 +469,7 @@ static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
 }
 
 /*
- * Dequeue a signal and return the element to the caller, which is 
+ * Dequeue a signal and return the element to the caller, which is
  * expected to free it.
  *
  * All callers have to hold the siglock.
@@ -490,7 +491,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
                  * itimers are process shared and we restart periodic
                  * itimers in the signal delivery path to prevent DoS
                  * attacks in the high resolution timer case. This is
-                 * compliant with the old way of self restarting
+                 * compliant with the old way of self-restarting
                  * itimers, as the SIGALRM is a legacy signal and only
                  * queued once. Changing the restart behaviour to
                  * restart the timer in the signal dequeue path is
@@ -636,13 +637,33 @@ static inline bool si_fromuser(const struct siginfo *info)
 }
 
 /*
+ * called with RCU read lock from check_kill_permission()
+ */
+static int kill_ok_by_cred(struct task_struct *t)
+{
+        const struct cred *cred = current_cred();
+        const struct cred *tcred = __task_cred(t);
+
+        if (cred->user->user_ns == tcred->user->user_ns &&
+            (cred->euid == tcred->suid ||
+             cred->euid == tcred->uid ||
+             cred->uid  == tcred->suid ||
+             cred->uid  == tcred->uid))
+                return 1;
+
+        if (ns_capable(tcred->user->user_ns, CAP_KILL))
+                return 1;
+
+        return 0;
+}
+
+/*
  * Bad permissions for sending the signal
  * - the caller must hold the RCU read lock
  */
 static int check_kill_permission(int sig, struct siginfo *info,
                                  struct task_struct *t)
 {
-        const struct cred *cred, *tcred;
         struct pid *sid;
         int error;
 
@@ -656,14 +677,8 @@ static int check_kill_permission(int sig, struct siginfo *info,
         if (error)
                 return error;
 
-        cred = current_cred();
-        tcred = __task_cred(t);
         if (!same_thread_group(current, t) &&
-            (cred->euid ^ tcred->suid) &&
-            (cred->euid ^ tcred->uid) &&
-            (cred->uid  ^ tcred->suid) &&
-            (cred->uid  ^ tcred->uid) &&
-            !capable(CAP_KILL)) {
+            !kill_ok_by_cred(t)) {
                 switch (sig) {
                 case SIGCONT:
                         sid = task_session(t);
@@ -909,14 +924,15 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
         if (info == SEND_SIG_FORCED)
                 goto out_set;
 
-        /* Real-time signals must be queued if sent by sigqueue, or
-           some other real-time mechanism.  It is implementation
-           defined whether kill() does so.  We attempt to do so, on
-           the principle of least surprise, but since kill is not
-           allowed to fail with EAGAIN when low on memory we just
-           make sure at least one signal gets delivered and don't
-           pass on the info struct.  */
-
+        /*
+         * Real-time signals must be queued if sent by sigqueue, or
+         * some other real-time mechanism.  It is implementation
+         * defined whether kill() does so.  We attempt to do so, on
+         * the principle of least surprise, but since kill is not
+         * allowed to fail with EAGAIN when low on memory we just
+         * make sure at least one signal gets delivered and don't
+         * pass on the info struct.
+         */
         if (sig < SIGRTMIN)
                 override_rlimit = (is_si_special(info) || info->si_code >= 0);
         else
@@ -1187,8 +1203,7 @@ retry:
         return error;
 }
 
-int
-kill_proc_info(int sig, struct siginfo *info, pid_t pid)
+int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
 {
         int error;
         rcu_read_lock();
@@ -1285,8 +1300,7 @@ static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
  * These are for backward compatibility with the rest of the kernel source.
  */
 
-int
-send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
+int send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 {
         /*
          * Make sure legacy kernel users don't send in bad values
@@ -1354,7 +1368,7 @@ EXPORT_SYMBOL(kill_pid);
  * These functions support sending signals using preallocated sigqueue
  * structures.  This is needed "because realtime applications cannot
  * afford to lose notifications of asynchronous events, like timer
- * expirations or I/O completions".  In the case of Posix Timers
+ * expirations or I/O completions".  In the case of POSIX Timers
  * we allocate the sigqueue structure from the timer_create.  If this
  * allocation fails we are able to report the failure to the application
  * with an EAGAIN error.
@@ -1539,7 +1553,7 @@ static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
         info.si_signo = SIGCHLD;
         info.si_errno = 0;
         /*
-         * see comment in do_notify_parent() abot the following 3 lines
+         * see comment in do_notify_parent() about the following 4 lines
          */
         rcu_read_lock();
         info.si_pid = task_pid_nr_ns(tsk, parent->nsproxy->pid_ns);
@@ -1597,7 +1611,7 @@ static inline int may_ptrace_stop(void)
 }
 
 /*
- * Return nonzero if there is a SIGKILL that should be waking us up.
+ * Return non-zero if there is a SIGKILL that should be waking us up.
  * Called with the siglock held.
  */
 static int sigkill_pending(struct task_struct *tsk)
@@ -1721,7 +1735,7 @@ void ptrace_notify(int exit_code)
 /*
  * This performs the stopping for SIGSTOP and other stop signals.
  * We have to stop all threads in the thread group.
- * Returns nonzero if we've actually stopped and released the siglock.
+ * Returns non-zero if we've actually stopped and released the siglock.
  * Returns zero if we didn't stop and still hold the siglock.
  */
 static int do_signal_stop(int signr)
@@ -1809,10 +1823,12 @@ static int ptrace_signal(int signr, siginfo_t *info,
 
         current->exit_code = 0;
 
-        /* Update the siginfo structure if the signal has
-           changed.  If the debugger wanted something
-           specific in the siginfo structure then it should
-           have updated *info via PTRACE_SETSIGINFO.  */
+        /*
+         * Update the siginfo structure if the signal has
+         * changed.  If the debugger wanted something
+         * specific in the siginfo structure then it should
+         * have updated *info via PTRACE_SETSIGINFO.
+         */
         if (signr != info->si_signo) {
                 info->si_signo = signr;
                 info->si_errno = 0;
@@ -1871,7 +1887,7 @@ relock:
         for (;;) {
                 struct k_sigaction *ka;
                 /*
-                 * Tracing can induce an artifical signal and choose sigaction.
+                 * Tracing can induce an artificial signal and choose sigaction.
                  * The return value in @signr determines the default action,
                  * but @info->si_signo is the signal number we will report.
                  */
@@ -2020,7 +2036,8 @@ void exit_signals(struct task_struct *tsk)
         if (!signal_pending(tsk))
                 goto out;
 
-        /* It could be that __group_complete_signal() choose us to
+        /*
+         * It could be that __group_complete_signal() choose us to
          * notify about group-wide signal. Another thread should be
          * woken now to take the signal since we will not.
          */
@@ -2058,6 +2075,9 @@ EXPORT_SYMBOL(unblock_all_signals);
  * System call entry points.
  */
 
+/**
+ *  sys_restart_syscall - restart a system call
+ */
 SYSCALL_DEFINE0(restart_syscall)
 {
         struct restart_block *restart = &current_thread_info()->restart_block;
@@ -2111,6 +2131,13 @@ int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
         return error;
 }
 
+/**
+ *  sys_rt_sigprocmask - change the list of currently blocked signals
+ *  @how: whether to add, remove, or set signals
+ *  @set: stores pending signals
+ *  @oset: previous value of signal mask if non-null
+ *  @sigsetsize: size of sigset_t type
+ */
 SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, set,
                 sigset_t __user *, oset, size_t, sigsetsize)
 {
@@ -2169,8 +2196,14 @@ long do_sigpending(void __user *set, unsigned long sigsetsize)
 
 out:
         return error;
-}       
+}
 
+/**
+ *  sys_rt_sigpending - examine a pending signal that has been raised
+ *                      while blocked
+ *  @set: stores pending signals
+ *  @sigsetsize: size of sigset_t type or larger
+ */
 SYSCALL_DEFINE2(rt_sigpending, sigset_t __user *, set, size_t, sigsetsize)
 {
         return do_sigpending(set, sigsetsize);
@@ -2219,9 +2252,9 @@ int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from)
                 err |= __put_user(from->si_trapno, &to->si_trapno);
 #endif
 #ifdef BUS_MCEERR_AO
-                /* 
+                /*
                  * Other callers might not initialize the si_lsb field,
-                 * so check explicitely for the right codes here.
+                 * so check explicitly for the right codes here.
                  */
                 if (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO)
                         err |= __put_user(from->si_addr_lsb, &to->si_addr_lsb);
@@ -2250,6 +2283,14 @@ int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from)
 
 #endif
 
+/**
+ *  sys_rt_sigtimedwait - synchronously wait for queued signals specified
+ *                      in @uthese
+ *  @uthese: queued signals to wait for
+ *  @uinfo: if non-null, the signal's siginfo is returned here
+ *  @uts: upper bound on process time suspension
+ *  @sigsetsize: size of sigset_t type
+ */
 SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
                 siginfo_t __user *, uinfo, const struct timespec __user *, uts,
                 size_t, sigsetsize)
@@ -2266,7 +2307,7 @@ SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
 
         if (copy_from_user(&these, uthese, sizeof(these)))
                 return -EFAULT;
-                
+
         /*
          * Invert the set of allowed signals to get those we
          * want to block.
@@ -2291,9 +2332,11 @@ SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
                                    + (ts.tv_sec || ts.tv_nsec));
 
                 if (timeout) {
-                        /* None ready -- temporarily unblock those we're
+                        /*
+                         * None ready -- temporarily unblock those we're
                          * interested while we are sleeping in so that we'll
-                         * be awakened when they arrive.  */
+                         * be awakened when they arrive.
+                         */
                         current->real_blocked = current->blocked;
                         sigandsets(&current->blocked, &current->blocked, &these);
                         recalc_sigpending();
@@ -2325,6 +2368,11 @@ SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
         return ret;
 }
 
+/**
+ *  sys_kill - send a signal to a process
+ *  @pid: the PID of the process
+ *  @sig: signal to be sent
+ */
 SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
 {
         struct siginfo info;
@@ -2400,7 +2448,11 @@ SYSCALL_DEFINE3(tgkill, pid_t, tgid, pid_t, pid, int, sig)
         return do_tkill(tgid, pid, sig);
 }
 
-/*
+/**
+ *  sys_tkill - send signal to one specific task
+ *  @pid: the PID of the task
+ *  @sig: signal to be sent
+ *
  *  Send a signal to only one task, even if it's a CLONE_THREAD task.
  */
 SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
@@ -2412,6 +2464,12 @@ SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
         return do_tkill(0, pid, sig);
 }
 
+/**
+ *  sys_rt_sigqueueinfo - send signal information to a signal
+ *  @pid: the PID of the thread
+ *  @sig: signal to be sent
+ *  @uinfo: signal info to be sent
+ */
 SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
                 siginfo_t __user *, uinfo)
 {
@@ -2421,9 +2479,13 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
                 return -EFAULT;
 
         /* Not even root can pretend to send signals from the kernel.
-           Nor can they impersonate a kill(), which adds source info.  */
-        if (info.si_code >= 0)
+         * Nor can they impersonate a kill()/tgkill(), which adds source info.
+         */
+        if (info.si_code >= 0 || info.si_code == SI_TKILL) {
+                /* We used to allow any < 0 si_code */
+                WARN_ON_ONCE(info.si_code < 0);
                 return -EPERM;
+        }
         info.si_signo = sig;
 
         /* POSIX.1b doesn't mention process groups.  */
@@ -2437,9 +2499,13 @@ long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
                 return -EINVAL;
 
         /* Not even root can pretend to send signals from the kernel.
-           Nor can they impersonate a kill(), which adds source info.  */
-        if (info->si_code >= 0)
+         * Nor can they impersonate a kill()/tgkill(), which adds source info.
+         */
+        if (info->si_code >= 0 || info->si_code == SI_TKILL) {
+                /* We used to allow any < 0 si_code */
+                WARN_ON_ONCE(info->si_code < 0);
                 return -EPERM;
+        }
         info->si_signo = sig;
 
         return do_send_specific(tgid, pid, sig, info);
@@ -2531,12 +2597,11 @@ do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long s
 
                 error = -EINVAL;
                 /*
-                 *
-                 * Note - this code used to test ss_flags incorrectly
+                 * Note - this code used to test ss_flags incorrectly:
                  *        old code may have been written using ss_flags==0
                  *        to mean ss_flags==SS_ONSTACK (as this was the only
                  *        way that worked) - this fix preserves that older
-                 *        mechanism
+                 *        mechanism.
                  */
                 if (ss_flags != SS_DISABLE && ss_flags != SS_ONSTACK && ss_flags != 0)
                         goto out;
@@ -2570,6 +2635,10 @@ out:
 
 #ifdef __ARCH_WANT_SYS_SIGPENDING
 
+/**
+ *  sys_sigpending - examine pending signals
+ *  @set: where mask of pending signal is returned
+ */
 SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, set)
 {
         return do_sigpending(set, sizeof(*set));
@@ -2578,8 +2647,15 @@ SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, set)
 #endif
 
 #ifdef __ARCH_WANT_SYS_SIGPROCMASK
-/* Some platforms have their own version with special arguments others
-   support only sys_rt_sigprocmask.  */
+/**
+ *  sys_sigprocmask - examine and change blocked signals
+ *  @how: whether to add, remove, or set signals
+ *  @set: signals to add or remove (if non-null)
+ *  @oset: previous value of signal mask if non-null
+ *
+ * Some platforms have their own version with special arguments;
+ * others support only sys_rt_sigprocmask.
+ */
 
 SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, set,
                 old_sigset_t __user *, oset)
@@ -2632,6 +2708,13 @@ out:
 #endif /* __ARCH_WANT_SYS_SIGPROCMASK */
 
 #ifdef __ARCH_WANT_SYS_RT_SIGACTION
+/**
+ *  sys_rt_sigaction - alter an action taken by a process
+ *  @sig: signal to be sent
+ *  @act: new sigaction
+ *  @oact: used to save the previous sigaction
+ *  @sigsetsize: size of sigset_t type
+ */
 SYSCALL_DEFINE4(rt_sigaction, int, sig,
                 const struct sigaction __user *, act,
                 struct sigaction __user *, oact,
@@ -2718,6 +2801,12 @@ SYSCALL_DEFINE0(pause)
 #endif
 
 #ifdef __ARCH_WANT_SYS_RT_SIGSUSPEND
+/**
+ *  sys_rt_sigsuspend - replace the signal mask for a value with the
+ *      @unewset value until a signal is received
+ *  @unewset: new signal mask value
+ *  @sigsetsize: size of sigset_t type
+ */
 SYSCALL_DEFINE2(rt_sigsuspend, sigset_t __user *, unewset, size_t, sigsetsize)
 {
         sigset_t newset;