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>

2 files changed, 4 insertions, 1 deletions

diff --git a/arch/unicore32/kernel/fpu-ucf64.c b/arch/unicore32/kernel/fpu-ucf64.c
index 12c8c9527b8e..d785955e1c29 100644
--- a/arch/unicore32/kernel/fpu-ucf64.c
+++ b/arch/unicore32/kernel/fpu-ucf64.c
@@ -56,7 +56,7 @@ void ucf64_raise_sigfpe(unsigned int sicode, struct pt_regs *regs)
 {
 	siginfo_t info;
 
-	memset(&info, 0, sizeof(info));
+	clear_siginfo(&info);
 
 	info.si_signo = SIGFPE;
 	info.si_code = sicode;
diff --git a/arch/unicore32/mm/fault.c b/arch/unicore32/mm/fault.c
index bbefcc46a45e..381473412937 100644
--- a/arch/unicore32/mm/fault.c
+++ b/arch/unicore32/mm/fault.c
@@ -125,6 +125,7 @@ static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
 	tsk->thread.address = addr;
 	tsk->thread.error_code = fsr;
 	tsk->thread.trap_no = 14;
+	clear_siginfo(&si);
 	si.si_signo = sig;
 	si.si_errno = 0;
 	si.si_code = code;
@@ -472,6 +473,7 @@ asmlinkage void do_DataAbort(unsigned long addr, unsigned int fsr,
 	printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
 	       inf->name, fsr, addr);
 
+	clear_siginfo(&info);
 	info.si_signo = inf->sig;
 	info.si_errno = 0;
 	info.si_code = inf->code;
@@ -491,6 +493,7 @@ asmlinkage void do_PrefetchAbort(unsigned long addr,
 	printk(KERN_ALERT "Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
 	       inf->name, ifsr, addr);
 
+	clear_siginfo(&info);
 	info.si_signo = inf->sig;
 	info.si_errno = 0;
 	info.si_code = inf->code;