[REVIEW][PATCH 4/5] signal: Extend siginfo_layout with SIL_FAULT_{MCEERR|BNDERR|PKUERR}

[Eric W. Biederman]

Update the siginfo_layout function and enum siginfo_layout to represent
all of the possible field layouts of struct siginfo.

This allows the uses of siginfo_layout in um and arm64 where they are testing
for SIL_FAULT to be more accurate as this rules out the other cases.

Further this allows the switch statements on siginfo_layout to be simpler
if perhaps a little more wordy.  Making it easier to understand what is
actually going on.

As SIL_FAULT_BNDERR and SIL_FAULT_PKUERR are never expected to appear
in signalfd just treat them as SIL_FAULT.  To include them would take
20 extra bytes an pretty much fill up what is left of
signalfd_siginfo.

Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
 fs/signalfd.c          | 24 ++++++++++-----
 include/linux/signal.h |  3 ++
 kernel/signal.c        | 81 ++++++++++++++++++++++++++++++++++----------------
 3 files changed, 75 insertions(+), 33 deletions(-)

diff --git a/fs/signalfd.c b/fs/signalfd.c
index f652249f59f9..cbb42f77a2bd 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -112,19 +112,27 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
 		new.ssi_band = kinfo->si_band;
 		new.ssi_fd   = kinfo->si_fd;
 		break;
+	case SIL_FAULT_BNDERR:
+	case SIL_FAULT_PKUERR:
+		/*
+		 * Fall through to the SIL_FAULT case.  Both SIL_FAULT_BNDERR
+		 * and SIL_FAULT_PKUERR are only generated by faults that
+		 * deliver them synchronously to userspace.  In case someone
+		 * injects one of these signals and signalfd catches it treat
+		 * it as SIL_FAULT.
+		 */
 	case SIL_FAULT:
 		new.ssi_addr = (long) kinfo->si_addr;
 #ifdef __ARCH_SI_TRAPNO
 		new.ssi_trapno = kinfo->si_trapno;
 #endif
-		/*
-		 * Other callers might not initialize the si_lsb field,
-		 * so check explicitly for the right codes here.
-		 */
-		if (kinfo->si_signo == SIGBUS &&
-		    ((kinfo->si_code == BUS_MCEERR_AR) ||
-		     (kinfo->si_code == BUS_MCEERR_AO)))
-			new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
+		break;
+	case SIL_FAULT_MCEERR:
+		new.ssi_addr = (long) kinfo->si_addr;
+#ifdef __ARCH_SI_TRAPNO
+		new.ssi_trapno = kinfo->si_trapno;
+#endif
+		new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
 		break;
 	case SIL_CHLD:
 		new.ssi_pid    = kinfo->si_pid;
diff --git a/include/linux/signal.h b/include/linux/signal.h
index a9bc7e1b077e..3c5200137b24 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -28,6 +28,9 @@ enum siginfo_layout {
 	SIL_TIMER,
 	SIL_POLL,
 	SIL_FAULT,
+	SIL_FAULT_MCEERR,
+	SIL_FAULT_BNDERR,
+	SIL_FAULT_PKUERR,
 	SIL_CHLD,
 	SIL_RT,
 	SIL_SYS,
diff --git a/kernel/signal.c b/kernel/signal.c
index 376b42f26e6d..8a85da8aaa7c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2820,8 +2820,19 @@ enum siginfo_layout siginfo_layout(int sig, int si_code)
 			[SIGPOLL] = { NSIGPOLL, SIL_POLL },
 			[SIGSYS]  = { NSIGSYS,  SIL_SYS },
 		};
-		if ((sig < ARRAY_SIZE(filter)) && (si_code <= filter[sig].limit))
+		if ((sig < ARRAY_SIZE(filter)) && (si_code <= filter[sig].limit)) {
 			layout = filter[sig].layout;
+			/* Handle the exceptions */
+			if ((sig == SIGBUS) &&
+			    (si_code >= BUS_MCEERR_AR) && (si_code <= BUS_MCEERR_AO))
+				layout = SIL_FAULT_MCEERR;
+			else if ((sig == SIGSEGV) && (si_code == SEGV_BNDERR))
+				layout = SIL_FAULT_BNDERR;
+#ifdef SEGV_PKUERR
+			else if ((sig == SIGSEGV) && (si_code == SEGV_PKUERR))
+				layout = SIL_FAULT_PKUERR;
+#endif
+		}
 		else if (si_code <= NSIGPOLL)
 			layout = SIL_POLL;
 	} else {
@@ -2878,19 +2889,28 @@ int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
 #ifdef __ARCH_SI_TRAPNO
 		new.si_trapno = from->si_trapno;
 #endif
-		if ((from->si_signo == SIGBUS) &&
-		    ((from->si_code == BUS_MCEERR_AR) ||
-		     (from->si_code == BUS_MCEERR_AO)))
-			new.si_addr_lsb = from->si_addr_lsb;
-
-		if ((from->si_signo == SIGSEGV) &&
-		    (from->si_code == SEGV_BNDERR)) {
-			new.si_lower = ptr_to_compat(from->si_lower);
-			new.si_upper = ptr_to_compat(from->si_upper);
-		}
-		if ((from->si_signo == SIGSEGV) &&
-		    (from->si_code == SEGV_PKUERR))
-			new.si_pkey = from->si_pkey;
+		break;
+	case SIL_FAULT_MCEERR:
+		new.si_addr = ptr_to_compat(from->si_addr);
+#ifdef __ARCH_SI_TRAPNO
+		new.si_trapno = from->si_trapno;
+#endif
+		new.si_addr_lsb = from->si_addr_lsb;
+		break;
+	case SIL_FAULT_BNDERR:
+		new.si_addr = ptr_to_compat(from->si_addr);
+#ifdef __ARCH_SI_TRAPNO
+		new.si_trapno = from->si_trapno;
+#endif
+		new.si_lower = ptr_to_compat(from->si_lower);
+		new.si_upper = ptr_to_compat(from->si_upper);
+		break;
+	case SIL_FAULT_PKUERR:
+		new.si_addr = ptr_to_compat(from->si_addr);
+#ifdef __ARCH_SI_TRAPNO
+		new.si_trapno = from->si_trapno;
+#endif
+		new.si_pkey = from->si_pkey;
 		break;
 	case SIL_CHLD:
 		new.si_pid    = from->si_pid;
@@ -2956,17 +2976,28 @@ int copy_siginfo_from_user32(struct siginfo *to,
 #ifdef __ARCH_SI_TRAPNO
 		to->si_trapno = from.si_trapno;
 #endif
-		if ((from.si_signo == SIGBUS) &&
-		    ((from.si_code == BUS_MCEERR_AR) ||
-		     (from.si_code == BUS_MCEERR_AO)))
-			to->si_addr_lsb = from.si_addr_lsb;
-
-		if ((from.si_signo == SIGSEGV) && (from.si_code == SEGV_BNDERR)) {
-			to->si_lower = compat_ptr(from.si_lower);
-			to->si_upper = compat_ptr(from.si_upper);
-		}
-		if ((from.si_signo == SIGSEGV) && (from.si_code == SEGV_PKUERR))
-			to->si_pkey = from.si_pkey;
+		break;
+	case SIL_FAULT_MCEERR:
+		to->si_addr = compat_ptr(from.si_addr);
+#ifdef __ARCH_SI_TRAPNO
+		to->si_trapno = from.si_trapno;
+#endif
+		to->si_addr_lsb = from.si_addr_lsb;
+		break;
+	case SIL_FAULT_BNDERR:
+		to->si_addr = compat_ptr(from.si_addr);
+#ifdef __ARCH_SI_TRAPNO
+		to->si_trapno = from.si_trapno;
+#endif
+		to->si_lower = compat_ptr(from.si_lower);
+		to->si_upper = compat_ptr(from.si_upper);
+		break;
+	case SIL_FAULT_PKUERR:
+		to->si_addr = compat_ptr(from.si_addr);
+#ifdef __ARCH_SI_TRAPNO
+		to->si_trapno = from.si_trapno;
+#endif
+		to->si_pkey = from.si_pkey;
 		break;
 	case SIL_CHLD:
 		to->si_pid    = from.si_pid;
-- 
2.14.1