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, 6 insertions, 0 deletions

diff --git a/arch/parisc/kernel/ptrace.c b/arch/parisc/kernel/ptrace.c
index 1a2be6e..b1c12ce 100644
--- a/arch/parisc/kernel/ptrace.c
+++ b/arch/parisc/kernel/ptrace.c
@@ -90,6 +90,7 @@ void user_enable_single_step(struct task_struct *task)
 		ptrace_disable(task);
 		/* Don't wake up the task, but let the
 		   parent know something happened. */
+		clear_siginfo(&si);
 		si.si_code = TRAP_TRACE;
 		si.si_addr = (void __user *) (task_regs(task)->iaoq[0] & ~3);
 		si.si_signo = SIGTRAP;
diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index 68e671a..98f9f2f 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -299,6 +299,7 @@ static void handle_gdb_break(struct pt_regs *regs, int wot)
 {
 	struct siginfo si;
 
+	clear_siginfo(&si);
 	si.si_signo = SIGTRAP;
 	si.si_errno = 0;
 	si.si_code = wot;
@@ -489,6 +490,7 @@ void notrace handle_interruption(int code, struct pt_regs *regs)
 	unsigned long fault_space = 0;
 	struct siginfo si;
 
+	clear_siginfo(&si);
 	if (code == 1)
 	    pdc_console_restart();  /* switch back to pdc if HPMC */
 	else
diff --git a/arch/parisc/kernel/unaligned.c b/arch/parisc/kernel/unaligned.c
index e36f7b7..30b7c7f 100644
--- a/arch/parisc/kernel/unaligned.c
+++ b/arch/parisc/kernel/unaligned.c
@@ -455,6 +455,7 @@ void handle_unaligned(struct pt_regs *regs)
 	struct siginfo si;
 	register int flop=0;	/* true if this is a flop */
 
+	clear_siginfo(&si);
 	__inc_irq_stat(irq_unaligned_count);
 
 	/* log a message with pacing */
diff --git a/arch/parisc/math-emu/driver.c b/arch/parisc/math-emu/driver.c
index 2fb59d2..0d10efb 100644
--- a/arch/parisc/math-emu/driver.c
+++ b/arch/parisc/math-emu/driver.c
@@ -93,6 +93,7 @@ handle_fpe(struct pt_regs *regs)
 	 */
 	__u64 frcopy[36];
 
+	clear_siginfo(&si);
 	memcpy(frcopy, regs->fr, sizeof regs->fr);
 	frcopy[32] = 0;
 
diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index e247edb..657b350 100644
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -356,6 +356,7 @@ bad_area:
 		struct siginfo si;
 		unsigned int lsb = 0;
 
+		clear_siginfo(&si);
 		switch (code) {
 		case 15:	/* Data TLB miss fault/Data page fault */
 			/* send SIGSEGV when outside of vma */