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

Pull siginfo updates from Eric Biederman:
 "I have been slowly sorting out siginfo and this is the culmination of
  that work.

  The primary result is in several ways the signal infrastructure has
  been made less error prone. The code has been updated so that manually
  specifying SEND_SIG_FORCED is never necessary. The conversion to the
  new siginfo sending functions is now complete, which makes it
  difficult to send a signal without filling in the proper siginfo
  fields.

  At the tail end of the patchset comes the optimization of decreasing
  the size of struct siginfo in the kernel from 128 bytes to about 48
  bytes on 64bit. The fundamental observation that enables this is by
  definition none of the known ways to use struct siginfo uses the extra
  bytes.

  This comes at the cost of a small user space observable difference.
  For the rare case of siginfo being injected into the kernel only what
  can be copied into kernel_siginfo is delivered to the destination, the
  rest of the bytes are set to 0. For cases where the signal and the
  si_code are known this is safe, because we know those bytes are not
  used. For cases where the signal and si_code combination is unknown
  the bits that won't fit into struct kernel_siginfo are tested to
  verify they are zero, and the send fails if they are not.

  I made an extensive search through userspace code and I could not find
  anything that would break because of the above change. If it turns out
  I did break something it will take just the revert of a single change
  to restore kernel_siginfo to the same size as userspace siginfo.

  Testing did reveal dependencies on preferring the signo passed to
  sigqueueinfo over si->signo, so bit the bullet and added the
  complexity necessary to handle that case.

  Testing also revealed bad things can happen if a negative signal
  number is passed into the system calls. Something no sane application
  will do but something a malicious program or a fuzzer might do. So I
  have fixed the code that performs the bounds checks to ensure negative
  signal numbers are handled"

* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (80 commits)
  signal: Guard against negative signal numbers in copy_siginfo_from_user32
  signal: Guard against negative signal numbers in copy_siginfo_from_user
  signal: In sigqueueinfo prefer sig not si_signo
  signal: Use a smaller struct siginfo in the kernel
  signal: Distinguish between kernel_siginfo and siginfo
  signal: Introduce copy_siginfo_from_user and use it's return value
  signal: Remove the need for __ARCH_SI_PREABLE_SIZE and SI_PAD_SIZE
  signal: Fail sigqueueinfo if si_signo != sig
  signal/sparc: Move EMT_TAGOVF into the generic siginfo.h
  signal/unicore32: Use force_sig_fault where appropriate
  signal/unicore32: Generate siginfo in ucs32_notify_die
  signal/unicore32: Use send_sig_fault where appropriate
  signal/arc: Use force_sig_fault where appropriate
  signal/arc: Push siginfo generation into unhandled_exception
  signal/ia64: Use force_sig_fault where appropriate
  signal/ia64: Use the force_sig(SIGSEGV,...) in ia64_rt_sigreturn
  signal/ia64: Use the generic force_sigsegv in setup_frame
  signal/arm/kvm: Use send_sig_mceerr
  signal/arm: Use send_sig_fault where appropriate
  signal/arm: Use force_sig_fault where appropriate
  ...

5 files changed, 52 insertions, 65 deletions

diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 06ca574495af..d7bb6aefae0a 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -210,13 +210,6 @@ NOKPROBE_SYMBOL(call_step_hook);
 static void send_user_sigtrap(int si_code)
 {
 	struct pt_regs *regs = current_pt_regs();
-	siginfo_t info;
-
-	clear_siginfo(&info);
-	info.si_signo	= SIGTRAP;
-	info.si_errno	= 0;
-	info.si_code	= si_code;
-	info.si_addr	= (void __user *)instruction_pointer(regs);
 
 	if (WARN_ON(!user_mode(regs)))
 		return;
@@ -224,7 +217,9 @@ static void send_user_sigtrap(int si_code)
 	if (interrupts_enabled(regs))
 		local_irq_enable();
 
-	arm64_force_sig_info(&info, "User debug trap", current);
+	arm64_force_sig_fault(SIGTRAP, si_code,
+			     (void __user *)instruction_pointer(regs),
+			     "User debug trap");
 }
 
 static int single_step_handler(unsigned long addr, unsigned int esr,
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 58c53bc96928..5ebe73b69961 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -842,7 +842,6 @@ asmlinkage void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
  */
 asmlinkage void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs)
 {
-	siginfo_t info;
 	unsigned int si_code = FPE_FLTUNK;
 
 	if (esr & ESR_ELx_FP_EXC_TFV) {
@@ -858,12 +857,9 @@ asmlinkage void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs)
 			si_code = FPE_FLTRES;
 	}
 
-	clear_siginfo(&info);
-	info.si_signo = SIGFPE;
-	info.si_code = si_code;
-	info.si_addr = (void __user *)instruction_pointer(regs);
-
-	send_sig_info(SIGFPE, &info, current);
+	send_sig_fault(SIGFPE, si_code,
+		       (void __user *)instruction_pointer(regs),
+		       current);
 }
 
 void fpsimd_thread_switch(struct task_struct *next)
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 6219486fa25f..1710a2d01669 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -182,13 +182,7 @@ static void ptrace_hbptriggered(struct perf_event *bp,
 				struct pt_regs *regs)
 {
 	struct arch_hw_breakpoint *bkpt = counter_arch_bp(bp);
-	siginfo_t info;
-
-	clear_siginfo(&info);
-	info.si_signo	= SIGTRAP;
-	info.si_errno	= 0;
-	info.si_code	= TRAP_HWBKPT;
-	info.si_addr	= (void __user *)(bkpt->trigger);
+	const char *desc = "Hardware breakpoint trap (ptrace)";
 
 #ifdef CONFIG_COMPAT
 	if (is_compat_task()) {
@@ -208,10 +202,14 @@ static void ptrace_hbptriggered(struct perf_event *bp,
 				break;
 			}
 		}
-		force_sig_ptrace_errno_trap(si_errno, (void __user *)bkpt->trigger);
+		arm64_force_sig_ptrace_errno_trap(si_errno,
+						  (void __user *)bkpt->trigger,
+						  desc);
 	}
 #endif
-	arm64_force_sig_info(&info, "Hardware breakpoint trap (ptrace)", current);
+	arm64_force_sig_fault(SIGTRAP, TRAP_HWBKPT,
+			      (void __user *)(bkpt->trigger),
+			      desc);
 }
 
 /*
diff --git a/arch/arm64/kernel/sys_compat.c b/arch/arm64/kernel/sys_compat.c
index a6109825eeb9..32653d156747 100644
--- a/arch/arm64/kernel/sys_compat.c
+++ b/arch/arm64/kernel/sys_compat.c
@@ -68,8 +68,8 @@ do_compat_cache_op(unsigned long start, unsigned long end, int flags)
  */
 long compat_arm_syscall(struct pt_regs *regs)
 {
-	siginfo_t info;
 	unsigned int no = regs->regs[7];
+	void __user *addr;
 
 	switch (no) {
 	/*
@@ -112,13 +112,10 @@ long compat_arm_syscall(struct pt_regs *regs)
 		break;
 	}
 
-	clear_siginfo(&info);
-	info.si_signo = SIGILL;
-	info.si_errno = 0;
-	info.si_code  = ILL_ILLTRP;
-	info.si_addr  = (void __user *)instruction_pointer(regs) -
-			 (compat_thumb_mode(regs) ? 2 : 4);
+	addr  = (void __user *)instruction_pointer(regs) -
+		(compat_thumb_mode(regs) ? 2 : 4);
 
-	arm64_notify_die("Oops - bad compat syscall(2)", regs, &info, no);
+	arm64_notify_die("Oops - bad compat syscall(2)", regs,
+			 SIGILL, ILL_ILLTRP, addr, no);
 	return 0;
 }
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 4066da7f1e5e..5f4d9acb32f5 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -224,24 +224,19 @@ void die(const char *str, struct pt_regs *regs, int err)
 		do_exit(SIGSEGV);
 }
 
-static bool show_unhandled_signals_ratelimited(void)
+static void arm64_show_signal(int signo, const char *str)
 {
 	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
 				      DEFAULT_RATELIMIT_BURST);
-	return show_unhandled_signals && __ratelimit(&rs);
-}
-
-void arm64_force_sig_info(struct siginfo *info, const char *str,
-			  struct task_struct *tsk)
-{
+	struct task_struct *tsk = current;
 	unsigned int esr = tsk->thread.fault_code;
 	struct pt_regs *regs = task_pt_regs(tsk);
 
-	if (!unhandled_signal(tsk, info->si_signo))
-		goto send_sig;
-
-	if (!show_unhandled_signals_ratelimited())
-		goto send_sig;
+	/* Leave if the signal won't be shown */
+	if (!show_unhandled_signals ||
+	    !unhandled_signal(tsk, signo) ||
+	    !__ratelimit(&rs))
+		return;
 
 	pr_info("%s[%d]: unhandled exception: ", tsk->comm, task_pid_nr(tsk));
 	if (esr)
@@ -251,19 +246,39 @@ void arm64_force_sig_info(struct siginfo *info, const char *str,
 	print_vma_addr(KERN_CONT " in ", regs->pc);
 	pr_cont("\n");
 	__show_regs(regs);
+}
+
+void arm64_force_sig_fault(int signo, int code, void __user *addr,
+			   const char *str)
+{
+	arm64_show_signal(signo, str);
+	force_sig_fault(signo, code, addr, current);
+}
 
-send_sig:
-	force_sig_info(info->si_signo, info, tsk);
+void arm64_force_sig_mceerr(int code, void __user *addr, short lsb,
+			    const char *str)
+{
+	arm64_show_signal(SIGBUS, str);
+	force_sig_mceerr(code, addr, lsb, current);
+}
+
+void arm64_force_sig_ptrace_errno_trap(int errno, void __user *addr,
+				       const char *str)
+{
+	arm64_show_signal(SIGTRAP, str);
+	force_sig_ptrace_errno_trap(errno, addr);
 }
 
 void arm64_notify_die(const char *str, struct pt_regs *regs,
-		      struct siginfo *info, int err)
+		      int signo, int sicode, void __user *addr,
+		      int err)
 {
 	if (user_mode(regs)) {
 		WARN_ON(regs != current_pt_regs());
 		current->thread.fault_address = 0;
 		current->thread.fault_code = err;
-		arm64_force_sig_info(info, str, current);
+
+		arm64_force_sig_fault(signo, sicode, addr, str);
 	} else {
 		die(str, regs, err);
 	}
@@ -350,15 +365,12 @@ exit:
 
 void force_signal_inject(int signal, int code, unsigned long address)
 {
-	siginfo_t info;
 	const char *desc;
 	struct pt_regs *regs = current_pt_regs();
 
 	if (WARN_ON(!user_mode(regs)))
 		return;
 
-	clear_siginfo(&info);
-
 	switch (signal) {
 	case SIGILL:
 		desc = "undefined instruction";
@@ -377,12 +389,7 @@ void force_signal_inject(int signal, int code, unsigned long address)
 		signal = SIGKILL;
 	}
 
-	info.si_signo = signal;
-	info.si_errno = 0;
-	info.si_code  = code;
-	info.si_addr  = (void __user *)address;
-
-	arm64_notify_die(desc, regs, &info, 0);
+	arm64_notify_die(desc, regs, signal, code, (void __user *)address, 0);
 }
 
 /*
@@ -799,19 +806,13 @@ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr)
  */
 asmlinkage void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr)
 {
-	siginfo_t info;
 	void __user *pc = (void __user *)instruction_pointer(regs);
 
-	clear_siginfo(&info);
-	info.si_signo = SIGILL;
-	info.si_errno = 0;
-	info.si_code  = ILL_ILLOPC;
-	info.si_addr  = pc;
-
 	current->thread.fault_address = 0;
 	current->thread.fault_code = esr;
 
-	arm64_force_sig_info(&info, "Bad EL0 synchronous exception", current);
+	arm64_force_sig_fault(SIGILL, ILL_ILLOPC, pc,
+			      "Bad EL0 synchronous exception");
 }
 
 #ifdef CONFIG_VMAP_STACK