Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull force_sig() argument change from Eric Biederman:
 "A source of error over the years has been that force_sig has taken a
  task parameter when it is only safe to use force_sig with the current
  task.

  The force_sig function is built for delivering synchronous signals
  such as SIGSEGV where the userspace application caused a synchronous
  fault (such as a page fault) and the kernel responded with a signal.

  Because the name force_sig does not make this clear, and because the
  force_sig takes a task parameter the function force_sig has been
  abused for sending other kinds of signals over the years. Slowly those
  have been fixed when the oopses have been tracked down.

  This set of changes fixes the remaining abusers of force_sig and
  carefully rips out the task parameter from force_sig and friends
  making this kind of error almost impossible in the future"

* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (27 commits)
  signal/x86: Move tsk inside of CONFIG_MEMORY_FAILURE in do_sigbus
  signal: Remove the signal number and task parameters from force_sig_info
  signal: Factor force_sig_info_to_task out of force_sig_info
  signal: Generate the siginfo in force_sig
  signal: Move the computation of force into send_signal and correct it.
  signal: Properly set TRACE_SIGNAL_LOSE_INFO in __send_signal
  signal: Remove the task parameter from force_sig_fault
  signal: Use force_sig_fault_to_task for the two calls that don't deliver to current
  signal: Explicitly call force_sig_fault on current
  signal/unicore32: Remove tsk parameter from __do_user_fault
  signal/arm: Remove tsk parameter from __do_user_fault
  signal/arm: Remove tsk parameter from ptrace_break
  signal/nds32: Remove tsk parameter from send_sigtrap
  signal/riscv: Remove tsk parameter from do_trap
  signal/sh: Remove tsk parameter from force_sig_info_fault
  signal/um: Remove task parameter from send_sigtrap
  signal/x86: Remove task parameter from send_sigtrap
  signal: Remove task parameter from force_sig_mceerr
  signal: Remove task parameter from force_sig
  signal: Remove task parameter from force_sigsegv
  ...

1 files changed, 174 insertions, 75 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 35e97f4073c2..91cb8ca41954 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1057,29 +1057,8 @@ static inline bool legacy_queue(struct sigpending *signals, int sig)
 	return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
 }
 
-#ifdef CONFIG_USER_NS
-static inline void userns_fixup_signal_uid(struct kernel_siginfo *info, struct task_struct *t)
-{
-	if (current_user_ns() == task_cred_xxx(t, user_ns))
-		return;
-
-	if (SI_FROMKERNEL(info))
-		return;
-
-	rcu_read_lock();
-	info->si_uid = from_kuid_munged(task_cred_xxx(t, user_ns),
-					make_kuid(current_user_ns(), info->si_uid));
-	rcu_read_unlock();
-}
-#else
-static inline void userns_fixup_signal_uid(struct kernel_siginfo *info, struct task_struct *t)
-{
-	return;
-}
-#endif
-
 static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t,
-			enum pid_type type, int from_ancestor_ns)
+			enum pid_type type, bool force)
 {
 	struct sigpending *pending;
 	struct sigqueue *q;
@@ -1089,8 +1068,7 @@ static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struc
 	assert_spin_locked(&t->sighand->siglock);
 
 	result = TRACE_SIGNAL_IGNORED;
-	if (!prepare_signal(sig, t,
-			from_ancestor_ns || (info == SEND_SIG_PRIV)))
+	if (!prepare_signal(sig, t, force))
 		goto ret;
 
 	pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;
@@ -1135,7 +1113,11 @@ static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struc
 			q->info.si_code = SI_USER;
 			q->info.si_pid = task_tgid_nr_ns(current,
 							task_active_pid_ns(t));
-			q->info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
+			rcu_read_lock();
+			q->info.si_uid =
+				from_kuid_munged(task_cred_xxx(t, user_ns),
+						 current_uid());
+			rcu_read_unlock();
 			break;
 		case (unsigned long) SEND_SIG_PRIV:
 			clear_siginfo(&q->info);
@@ -1147,30 +1129,24 @@ static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struc
 			break;
 		default:
 			copy_siginfo(&q->info, info);
-			if (from_ancestor_ns)
-				q->info.si_pid = 0;
 			break;
 		}
-
-		userns_fixup_signal_uid(&q->info, t);
-
-	} else if (!is_si_special(info)) {
-		if (sig >= SIGRTMIN && info->si_code != SI_USER) {
-			/*
-			 * Queue overflow, abort.  We may abort if the
-			 * signal was rt and sent by user using something
-			 * other than kill().
-			 */
-			result = TRACE_SIGNAL_OVERFLOW_FAIL;
-			ret = -EAGAIN;
-			goto ret;
-		} else {
-			/*
-			 * This is a silent loss of information.  We still
-			 * send the signal, but the *info bits are lost.
-			 */
-			result = TRACE_SIGNAL_LOSE_INFO;
-		}
+	} else if (!is_si_special(info) &&
+		   sig >= SIGRTMIN && info->si_code != SI_USER) {
+		/*
+		 * Queue overflow, abort.  We may abort if the
+		 * signal was rt and sent by user using something
+		 * other than kill().
+		 */
+		result = TRACE_SIGNAL_OVERFLOW_FAIL;
+		ret = -EAGAIN;
+		goto ret;
+	} else {
+		/*
+		 * This is a silent loss of information.  We still
+		 * send the signal, but the *info bits are lost.
+		 */
+		result = TRACE_SIGNAL_LOSE_INFO;
 	}
 
 out_set:
@@ -1197,17 +1173,62 @@ ret:
 	return ret;
 }
 
+static inline bool has_si_pid_and_uid(struct kernel_siginfo *info)
+{
+	bool ret = false;
+	switch (siginfo_layout(info->si_signo, info->si_code)) {
+	case SIL_KILL:
+	case SIL_CHLD:
+	case SIL_RT:
+		ret = true;
+		break;
+	case SIL_TIMER:
+	case SIL_POLL:
+	case SIL_FAULT:
+	case SIL_FAULT_MCEERR:
+	case SIL_FAULT_BNDERR:
+	case SIL_FAULT_PKUERR:
+	case SIL_SYS:
+		ret = false;
+		break;
+	}
+	return ret;
+}
+
 static int send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t,
 			enum pid_type type)
 {
-	int from_ancestor_ns = 0;
+	/* Should SIGKILL or SIGSTOP be received by a pid namespace init? */
+	bool force = false;
 
-#ifdef CONFIG_PID_NS
-	from_ancestor_ns = si_fromuser(info) &&
-			   !task_pid_nr_ns(current, task_active_pid_ns(t));
-#endif
+	if (info == SEND_SIG_NOINFO) {
+		/* Force if sent from an ancestor pid namespace */
+		force = !task_pid_nr_ns(current, task_active_pid_ns(t));
+	} else if (info == SEND_SIG_PRIV) {
+		/* Don't ignore kernel generated signals */
+		force = true;
+	} else if (has_si_pid_and_uid(info)) {
+		/* SIGKILL and SIGSTOP is special or has ids */
+		struct user_namespace *t_user_ns;
+
+		rcu_read_lock();
+		t_user_ns = task_cred_xxx(t, user_ns);
+		if (current_user_ns() != t_user_ns) {
+			kuid_t uid = make_kuid(current_user_ns(), info->si_uid);
+			info->si_uid = from_kuid_munged(t_user_ns, uid);
+		}
+		rcu_read_unlock();
 
-	return __send_signal(sig, info, t, type, from_ancestor_ns);
+		/* A kernel generated signal? */
+		force = (info->si_code == SI_KERNEL);
+
+		/* From an ancestor pid namespace? */
+		if (!task_pid_nr_ns(current, task_active_pid_ns(t))) {
+			info->si_pid = 0;
+			force = true;
+		}
+	}
+	return __send_signal(sig, info, t, type, force);
 }
 
 static void print_fatal_signal(int signr)
@@ -1274,12 +1295,13 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p
  * We don't want to have recursive SIGSEGV's etc, for example,
  * that is why we also clear SIGNAL_UNKILLABLE.
  */
-int
-force_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *t)
+static int
+force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t)
 {
 	unsigned long int flags;
 	int ret, blocked, ignored;
 	struct k_sigaction *action;
+	int sig = info->si_signo;
 
 	spin_lock_irqsave(&t->sighand->siglock, flags);
 	action = &t->sighand->action[sig-1];
@@ -1304,6 +1326,11 @@ force_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *t)
 	return ret;
 }
 
+int force_sig_info(struct kernel_siginfo *info)
+{
+	return force_sig_info_to_task(info, current);
+}
+
 /*
  * Nuke all other threads in the group.
  */
@@ -1440,13 +1467,44 @@ static inline bool kill_as_cred_perm(const struct cred *cred,
 	       uid_eq(cred->uid, pcred->uid);
 }
 
-/* like kill_pid_info(), but doesn't use uid/euid of "current" */
-int kill_pid_info_as_cred(int sig, struct kernel_siginfo *info, struct pid *pid,
-			 const struct cred *cred)
+/*
+ * The usb asyncio usage of siginfo is wrong.  The glibc support
+ * for asyncio which uses SI_ASYNCIO assumes the layout is SIL_RT.
+ * AKA after the generic fields:
+ *	kernel_pid_t	si_pid;
+ *	kernel_uid32_t	si_uid;
+ *	sigval_t	si_value;
+ *
+ * Unfortunately when usb generates SI_ASYNCIO it assumes the layout
+ * after the generic fields is:
+ *	void __user 	*si_addr;
+ *
+ * This is a practical problem when there is a 64bit big endian kernel
+ * and a 32bit userspace.  As the 32bit address will encoded in the low
+ * 32bits of the pointer.  Those low 32bits will be stored at higher
+ * address than appear in a 32 bit pointer.  So userspace will not
+ * see the address it was expecting for it's completions.
+ *
+ * There is nothing in the encoding that can allow
+ * copy_siginfo_to_user32 to detect this confusion of formats, so
+ * handle this by requiring the caller of kill_pid_usb_asyncio to
+ * notice when this situration takes place and to store the 32bit
+ * pointer in sival_int, instead of sival_addr of the sigval_t addr
+ * parameter.
+ */
+int kill_pid_usb_asyncio(int sig, int errno, sigval_t addr,
+			 struct pid *pid, const struct cred *cred)
 {
-	int ret = -EINVAL;
+	struct kernel_siginfo info;
 	struct task_struct *p;
 	unsigned long flags;
+	int ret = -EINVAL;
+
+	clear_siginfo(&info);
+	info.si_signo = sig;
+	info.si_errno = errno;
+	info.si_code = SI_ASYNCIO;
+	*((sigval_t *)&info.si_pid) = addr;
 
 	if (!valid_signal(sig))
 		return ret;
@@ -1457,17 +1515,17 @@ int kill_pid_info_as_cred(int sig, struct kernel_siginfo *info, struct pid *pid,
 		ret = -ESRCH;
 		goto out_unlock;
 	}
-	if (si_fromuser(info) && !kill_as_cred_perm(cred, p)) {
+	if (!kill_as_cred_perm(cred, p)) {
 		ret = -EPERM;
 		goto out_unlock;
 	}
-	ret = security_task_kill(p, info, sig, cred);
+	ret = security_task_kill(p, &info, sig, cred);
 	if (ret)
 		goto out_unlock;
 
 	if (sig) {
 		if (lock_task_sighand(p, &flags)) {
-			ret = __send_signal(sig, info, p, PIDTYPE_TGID, 0);
+			ret = __send_signal(sig, &info, p, PIDTYPE_TGID, false);
 			unlock_task_sighand(p, &flags);
 		} else
 			ret = -ESRCH;
@@ -1476,7 +1534,7 @@ out_unlock:
 	rcu_read_unlock();
 	return ret;
 }
-EXPORT_SYMBOL_GPL(kill_pid_info_as_cred);
+EXPORT_SYMBOL_GPL(kill_pid_usb_asyncio);
 
 /*
  * kill_something_info() interprets pid in interesting ways just like kill(2).
@@ -1552,9 +1610,17 @@ send_sig(int sig, struct task_struct *p, int priv)
 }
 EXPORT_SYMBOL(send_sig);
 
-void force_sig(int sig, struct task_struct *p)
+void force_sig(int sig)
 {
-	force_sig_info(sig, SEND_SIG_PRIV, p);
+	struct kernel_siginfo info;
+
+	clear_siginfo(&info);
+	info.si_signo = sig;
+	info.si_errno = 0;
+	info.si_code = SI_KERNEL;
+	info.si_pid = 0;
+	info.si_uid = 0;
+	force_sig_info(&info);
 }
 EXPORT_SYMBOL(force_sig);
 
@@ -1564,18 +1630,20 @@ EXPORT_SYMBOL(force_sig);
  * the problem was already a SIGSEGV, we'll want to
  * make sure we don't even try to deliver the signal..
  */
-void force_sigsegv(int sig, struct task_struct *p)
+void force_sigsegv(int sig)
 {
+	struct task_struct *p = current;
+
 	if (sig == SIGSEGV) {
 		unsigned long flags;
 		spin_lock_irqsave(&p->sighand->siglock, flags);
 		p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
 		spin_unlock_irqrestore(&p->sighand->siglock, flags);
 	}
-	force_sig(SIGSEGV, p);
+	force_sig(SIGSEGV);
 }
 
-int force_sig_fault(int sig, int code, void __user *addr
+int force_sig_fault_to_task(int sig, int code, void __user *addr
 	___ARCH_SI_TRAPNO(int trapno)
 	___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
 	, struct task_struct *t)
@@ -1595,7 +1663,16 @@ int force_sig_fault(int sig, int code, void __user *addr
 	info.si_flags = flags;
 	info.si_isr = isr;
 #endif
-	return force_sig_info(info.si_signo, &info, t);
+	return force_sig_info_to_task(&info, t);
+}
+
+int force_sig_fault(int sig, int code, void __user *addr
+	___ARCH_SI_TRAPNO(int trapno)
+	___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr))
+{
+	return force_sig_fault_to_task(sig, code, addr
+				       ___ARCH_SI_TRAPNO(trapno)
+				       ___ARCH_SI_IA64(imm, flags, isr), current);
 }
 
 int send_sig_fault(int sig, int code, void __user *addr
@@ -1621,7 +1698,7 @@ int send_sig_fault(int sig, int code, void __user *addr
 	return send_sig_info(info.si_signo, &info, t);
 }
 
-int force_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct *t)
+int force_sig_mceerr(int code, void __user *addr, short lsb)
 {
 	struct kernel_siginfo info;
 
@@ -1632,7 +1709,7 @@ int force_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct
 	info.si_code = code;
 	info.si_addr = addr;
 	info.si_addr_lsb = lsb;
-	return force_sig_info(info.si_signo, &info, t);
+	return force_sig_info(&info);
 }
 
 int send_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct *t)
@@ -1661,7 +1738,7 @@ int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper)
 	info.si_addr  = addr;
 	info.si_lower = lower;
 	info.si_upper = upper;
-	return force_sig_info(info.si_signo, &info, current);
+	return force_sig_info(&info);
 }
 
 #ifdef SEGV_PKUERR
@@ -1675,7 +1752,7 @@ int force_sig_pkuerr(void __user *addr, u32 pkey)
 	info.si_code  = SEGV_PKUERR;
 	info.si_addr  = addr;
 	info.si_pkey  = pkey;
-	return force_sig_info(info.si_signo, &info, current);
+	return force_sig_info(&info);
 }
 #endif
 
@@ -1691,7 +1768,7 @@ int force_sig_ptrace_errno_trap(int errno, void __user *addr)
 	info.si_errno = errno;
 	info.si_code  = TRAP_HWBKPT;
 	info.si_addr  = addr;
-	return force_sig_info(info.si_signo, &info, current);
+	return force_sig_info(&info);
 }
 
 int kill_pgrp(struct pid *pid, int sig, int priv)
@@ -2676,7 +2753,7 @@ static void signal_delivered(struct ksignal *ksig, int stepping)
 void signal_setup_done(int failed, struct ksignal *ksig, int stepping)
 {
 	if (failed)
-		force_sigsegv(ksig->sig, current);
+		force_sigsegv(ksig->sig);
 	else
 		signal_delivered(ksig, stepping);
 }
@@ -4477,6 +4554,28 @@ static inline void siginfo_buildtime_checks(void)
 	CHECK_OFFSET(si_syscall);
 	CHECK_OFFSET(si_arch);
 #undef CHECK_OFFSET
+
+	/* usb asyncio */
+	BUILD_BUG_ON(offsetof(struct siginfo, si_pid) !=
+		     offsetof(struct siginfo, si_addr));
+	if (sizeof(int) == sizeof(void __user *)) {
+		BUILD_BUG_ON(sizeof_field(struct siginfo, si_pid) !=
+			     sizeof(void __user *));
+	} else {
+		BUILD_BUG_ON((sizeof_field(struct siginfo, si_pid) +
+			      sizeof_field(struct siginfo, si_uid)) !=
+			     sizeof(void __user *));
+		BUILD_BUG_ON(offsetofend(struct siginfo, si_pid) !=
+			     offsetof(struct siginfo, si_uid));
+	}
+#ifdef CONFIG_COMPAT
+	BUILD_BUG_ON(offsetof(struct compat_siginfo, si_pid) !=
+		     offsetof(struct compat_siginfo, si_addr));
+	BUILD_BUG_ON(sizeof_field(struct compat_siginfo, si_pid) !=
+		     sizeof(compat_uptr_t));
+	BUILD_BUG_ON(sizeof_field(struct compat_siginfo, si_pid) !=
+		     sizeof_field(struct siginfo, si_pid));
+#endif
 }
 
 void __init signals_init(void)