signal/ptrace: Add force_sig_ptrace_errno_trap and use it where needed

There are so many places that build struct siginfo by hand that at
least one of them is bound to get it wrong.  A handful of cases in the
kernel arguably did just that when using the errno field of siginfo to
pass no errno values to userspace.  The usage is limited to a single
si_code so at least does not mess up anything else.

Encapsulate this questionable pattern in a helper function so
that the userspace ABI is preserved.

Update all of the places that use this pattern to use the new helper
function.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 95daa1478a7c..6618036ae6d4 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -190,21 +190,23 @@ static void ptrace_hbptriggered(struct perf_event *bp,
 
 #ifdef CONFIG_COMPAT
 	if (is_compat_task()) {
+		int si_errno = 0;
 		int i;
 
 		for (i = 0; i < ARM_MAX_BRP; ++i) {
 			if (current->thread.debug.hbp_break[i] == bp) {
-				info.si_errno = (i << 1) + 1;
+				si_errno = (i << 1) + 1;
 				break;
 			}
 		}
 
 		for (i = 0; i < ARM_MAX_WRP; ++i) {
 			if (current->thread.debug.hbp_watch[i] == bp) {
-				info.si_errno = -((i << 1) + 1);
+				si_errno = -((i << 1) + 1);
 				break;
 			}
 		}
+		force_sig_ptrace_errno_trap(si_errno, (void __user *)bkpt->trigger);
 	}
 #endif
 	force_sig_info(SIGTRAP, &info, current);