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>

1 files changed, 12 insertions, 6 deletions

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 4165485e8b6e..91c53a7d2575 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -305,11 +305,12 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re
 	 */
 	if (user_mode(regs)) {
 		const struct fault_info *inf = esr_to_fault_info(esr);
-		struct siginfo si = {
-			.si_signo	= inf->sig,
-			.si_code	= inf->code,
-			.si_addr	= (void __user *)addr,
-		};
+		struct siginfo si;
+
+		clear_siginfo(&si);
+		si.si_signo	= inf->sig;
+		si.si_code	= inf->code;
+		si.si_addr	= (void __user *)addr;
 
 		__do_user_fault(&si, esr);
 	} else {
@@ -583,6 +584,7 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
 			nmi_exit();
 	}
 
+	clear_siginfo(&info);
 	info.si_signo = inf->sig;
 	info.si_errno = 0;
 	info.si_code  = inf->code;
@@ -687,6 +689,7 @@ asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
 		show_pte(addr);
 	}
 
+	clear_siginfo(&info);
 	info.si_signo = inf->sig;
 	info.si_errno = 0;
 	info.si_code  = inf->code;
@@ -729,6 +732,7 @@ asmlinkage void __exception do_sp_pc_abort(unsigned long addr,
 		local_irq_enable();
 	}
 
+	clear_siginfo(&info);
 	info.si_signo = SIGBUS;
 	info.si_errno = 0;
 	info.si_code  = BUS_ADRALN;
@@ -772,7 +776,6 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
 					      struct pt_regs *regs)
 {
 	const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr);
-	struct siginfo info;
 	int rv;
 
 	/*
@@ -788,6 +791,9 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
 	if (!inf->fn(addr, esr, regs)) {
 		rv = 1;
 	} else {
+		struct siginfo info;
+
+		clear_siginfo(&info);
 		info.si_signo = inf->sig;
 		info.si_errno = 0;
 		info.si_code  = inf->code;