signal: Ensure every siginfo we send has all bits initialized

Call clear_siginfo to ensure every stack allocated siginfo is properly
initialized before being passed to the signal sending functions.

Note: It is not safe to depend on C initializers to initialize struct
siginfo on the stack because C is allowed to skip holes when
initializing a structure.

The initialization of struct siginfo in tracehook_report_syscall_exit
was moved from the helper user_single_step_siginfo into
tracehook_report_syscall_exit itself, to make it clear that the local
variable siginfo gets fully initialized.

In a few cases the scope of struct siginfo has been reduced to make it
clear that siginfo siginfo is not used on other paths in the function
in which it is declared.

Instances of using memset to initialize siginfo have been replaced
with calls clear_siginfo for clarity.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

5 files changed, 31 insertions, 4 deletions

diff --git a/arch/ia64/kernel/brl_emu.c b/arch/ia64/kernel/brl_emu.c
index 9bcc908bc85e..a61f6c6a36f8 100644
--- a/arch/ia64/kernel/brl_emu.c
+++ b/arch/ia64/kernel/brl_emu.c
@@ -62,6 +62,7 @@ ia64_emulate_brl (struct pt_regs *regs, unsigned long ar_ec)
 	struct illegal_op_return rv;
 	long tmp_taken, unimplemented_address;
 
+	clear_siginfo(&siginfo);
 	rv.fkt = (unsigned long) -1;
 
 	/*
diff --git a/arch/ia64/kernel/signal.c b/arch/ia64/kernel/signal.c
index 54547c7cf8a2..d1234a5ba4c5 100644
--- a/arch/ia64/kernel/signal.c
+++ b/arch/ia64/kernel/signal.c
@@ -153,6 +153,7 @@ ia64_rt_sigreturn (struct sigscratch *scr)
 	return retval;
 
   give_sigsegv:
+	clear_siginfo(&si);
 	si.si_signo = SIGSEGV;
 	si.si_errno = 0;
 	si.si_code = SI_KERNEL;
@@ -236,6 +237,7 @@ force_sigsegv_info (int sig, void __user *addr)
 	unsigned long flags;
 	struct siginfo si;
 
+	clear_siginfo(&si);
 	if (sig == SIGSEGV) {
 		/*
 		 * Acquiring siglock around the sa_handler-update is almost
diff --git a/arch/ia64/kernel/traps.c b/arch/ia64/kernel/traps.c
index 6d4e76a4267f..972873ed1ae5 100644
--- a/arch/ia64/kernel/traps.c
+++ b/arch/ia64/kernel/traps.c
@@ -104,6 +104,7 @@ __kprobes ia64_bad_break (unsigned long break_num, struct pt_regs *regs)
 	int sig, code;
 
 	/* SIGILL, SIGFPE, SIGSEGV, and SIGBUS want these field initialized: */
+	clear_siginfo(&siginfo);
 	siginfo.si_addr = (void __user *) (regs->cr_iip + ia64_psr(regs)->ri);
 	siginfo.si_imm = break_num;
 	siginfo.si_flags = 0;		/* clear __ISR_VALID */
@@ -293,7 +294,6 @@ handle_fpu_swa (int fp_fault, struct pt_regs *regs, unsigned long isr)
 {
 	long exception, bundle[2];
 	unsigned long fault_ip;
-	struct siginfo siginfo;
 
 	fault_ip = regs->cr_iip;
 	if (!fp_fault && (ia64_psr(regs)->ri == 0))
@@ -344,10 +344,13 @@ handle_fpu_swa (int fp_fault, struct pt_regs *regs, unsigned long isr)
 			printk(KERN_ERR "handle_fpu_swa: fp_emulate() returned -1\n");
 			return -1;
 		} else {
+			struct siginfo siginfo;
+
 			/* is next instruction a trap? */
 			if (exception & 2) {
 				ia64_increment_ip(regs);
 			}
+			clear_siginfo(&siginfo);
 			siginfo.si_signo = SIGFPE;
 			siginfo.si_errno = 0;
 			siginfo.si_code = FPE_FIXME;	/* default code */
@@ -372,6 +375,9 @@ handle_fpu_swa (int fp_fault, struct pt_regs *regs, unsigned long isr)
 			return -1;
 		} else if (exception != 0) {
 			/* raise exception */
+			struct siginfo siginfo;
+
+			clear_siginfo(&siginfo);
 			siginfo.si_signo = SIGFPE;
 			siginfo.si_errno = 0;
 			siginfo.si_code = FPE_FIXME;	/* default code */
@@ -420,7 +426,7 @@ ia64_illegal_op_fault (unsigned long ec, long arg1, long arg2, long arg3,
 	if (die_if_kernel(buf, &regs, 0))
 		return rv;
 
-	memset(&si, 0, sizeof(si));
+	clear_siginfo(&si);
 	si.si_signo = SIGILL;
 	si.si_code = ILL_ILLOPC;
 	si.si_addr = (void __user *) (regs.cr_iip + ia64_psr(&regs)->ri);
@@ -434,7 +440,6 @@ ia64_fault (unsigned long vector, unsigned long isr, unsigned long ifa,
 	    long arg7, struct pt_regs regs)
 {
 	unsigned long code, error = isr, iip;
-	struct siginfo siginfo;
 	char buf[128];
 	int result, sig;
 	static const char *reason[] = {
@@ -485,6 +490,7 @@ ia64_fault (unsigned long vector, unsigned long isr, unsigned long ifa,
 
 	      case 26: /* NaT Consumption */
 		if (user_mode(&regs)) {
+			struct siginfo siginfo;
 			void __user *addr;
 
 			if (((isr >> 4) & 0xf) == 2) {
@@ -499,6 +505,7 @@ ia64_fault (unsigned long vector, unsigned long isr, unsigned long ifa,
 				addr = (void __user *) (regs.cr_iip
 							+ ia64_psr(&regs)->ri);
 			}
+			clear_siginfo(&siginfo);
 			siginfo.si_signo = sig;
 			siginfo.si_code = code;
 			siginfo.si_errno = 0;
@@ -515,6 +522,9 @@ ia64_fault (unsigned long vector, unsigned long isr, unsigned long ifa,
 
 	      case 31: /* Unsupported Data Reference */
 		if (user_mode(&regs)) {
+			struct siginfo siginfo;
+
+			clear_siginfo(&siginfo);
 			siginfo.si_signo = SIGILL;
 			siginfo.si_code = ILL_ILLOPN;
 			siginfo.si_errno = 0;
@@ -531,6 +541,10 @@ ia64_fault (unsigned long vector, unsigned long isr, unsigned long ifa,
 	      case 29: /* Debug */
 	      case 35: /* Taken Branch Trap */
 	      case 36: /* Single Step Trap */
+	      {
+		struct siginfo siginfo;
+
+		clear_siginfo(&siginfo);
 		if (fsys_mode(current, &regs)) {
 			extern char __kernel_syscall_via_break[];
 			/*
@@ -578,11 +592,15 @@ ia64_fault (unsigned long vector, unsigned long isr, unsigned long ifa,
 		siginfo.si_isr   = isr;
 		force_sig_info(SIGTRAP, &siginfo, current);
 		return;
+	      }
 
 	      case 32: /* fp fault */
 	      case 33: /* fp trap */
 		result = handle_fpu_swa((vector == 32) ? 1 : 0, &regs, isr);
 		if ((result < 0) || (current->thread.flags & IA64_THREAD_FPEMU_SIGFPE)) {
+			struct siginfo siginfo;
+
+			clear_siginfo(&siginfo);
 			siginfo.si_signo = SIGFPE;
 			siginfo.si_errno = 0;
 			siginfo.si_code = FPE_FLTINV;
@@ -616,6 +634,9 @@ ia64_fault (unsigned long vector, unsigned long isr, unsigned long ifa,
 		} else {
 			/* Unimplemented Instr. Address Trap */
 			if (user_mode(&regs)) {
+				struct siginfo siginfo;
+
+				clear_siginfo(&siginfo);
 				siginfo.si_signo = SIGILL;
 				siginfo.si_code = ILL_BADIADDR;
 				siginfo.si_errno = 0;
diff --git a/arch/ia64/kernel/unaligned.c b/arch/ia64/kernel/unaligned.c
index 72e9b4242564..e309f9859acc 100644
--- a/arch/ia64/kernel/unaligned.c
+++ b/arch/ia64/kernel/unaligned.c
@@ -1537,6 +1537,7 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs)
 		/* NOT_REACHED */
 	}
   force_sigbus:
+	clear_siginfo(&si);
 	si.si_signo = SIGBUS;
 	si.si_errno = 0;
 	si.si_code = BUS_ADRALN;
diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index dfdc152d6737..817fa120645f 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -85,7 +85,6 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
 	int signal = SIGSEGV, code = SEGV_MAPERR;
 	struct vm_area_struct *vma, *prev_vma;
 	struct mm_struct *mm = current->mm;
-	struct siginfo si;
 	unsigned long mask;
 	int fault;
 	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
@@ -249,6 +248,9 @@ retry:
 		return;
 	}
 	if (user_mode(regs)) {
+		struct siginfo si;
+
+		clear_siginfo(&si);
 		si.si_signo = signal;
 		si.si_errno = 0;
 		si.si_code = code;