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, 4 insertions, 0 deletions

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index b75eada23d0a..32034543f49c 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -163,6 +163,8 @@ __do_user_fault(struct task_struct *tsk, unsigned long addr,
 {
         struct siginfo si;
 
+        clear_siginfo(&si);
+
 #ifdef CONFIG_DEBUG_USER
         if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
             ((user_debug & UDBG_BUS)  && (sig == SIGBUS))) {
@@ -557,6 +559,7 @@ do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
                 inf->name, fsr, addr);
         show_pte(current->mm, addr);
 
+        clear_siginfo(&info);
         info.si_signo = inf->sig;
         info.si_errno = 0;
         info.si_code  = inf->code;
@@ -589,6 +592,7 @@ do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
         pr_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;