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, 2 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 1237f13fed51..26ea9793d290 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -632,6 +632,7 @@ void do_break (struct pt_regs *regs, unsigned long address,
         hw_breakpoint_disable();
 
         /* Deliver the signal to userspace */
+        clear_siginfo(&info);
         info.si_signo = SIGTRAP;
         info.si_errno = 0;
         info.si_code = TRAP_HWBKPT;
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 0904492e7032..087855caf6a9 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -296,7 +296,6 @@ NOKPROBE_SYMBOL(die);
 void user_single_step_siginfo(struct task_struct *tsk,
                                 struct pt_regs *regs, siginfo_t *info)
 {
-        memset(info, 0, sizeof(*info));
         info->si_signo = SIGTRAP;
         info->si_code = TRAP_TRACE;
         info->si_addr = (void __user *)regs->nip;
@@ -334,7 +333,7 @@ void _exception_pkey(int signr, struct pt_regs *regs, int code,
          */
         thread_pkey_regs_save(&current->thread);
 
-        memset(&info, 0, sizeof(info));
+        clear_siginfo(&info);
         info.si_signo = signr;
         info.si_code = code;
         info.si_addr = (void __user *) addr;