1 files changed, 139 insertions, 3 deletions

diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c
index dc3c0b1c816f..40df33753bae 100644
--- a/arch/x86/kernel/signal_compat.c
+++ b/arch/x86/kernel/signal_compat.c
@@ -1,10 +1,125 @@
 #include <linux/compat.h>
 #include <linux/uaccess.h>
+#include <linux/ptrace.h>
 
-int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
+/*
+ * The compat_siginfo_t structure and handing code is very easy
+ * to break in several ways.  It must always be updated when new
+ * updates are made to the main siginfo_t, and
+ * copy_siginfo_to_user32() must be updated when the
+ * (arch-independent) copy_siginfo_to_user() is updated.
+ *
+ * It is also easy to put a new member in the compat_siginfo_t
+ * which has implicit alignment which can move internal structure
+ * alignment around breaking the ABI.  This can happen if you,
+ * for instance, put a plain 64-bit value in there.
+ */
+static inline void signal_compat_build_tests(void)
+{
+	int _sifields_offset = offsetof(compat_siginfo_t, _sifields);
+
+	/*
+	 * If adding a new si_code, there is probably new data in
+	 * the siginfo.  Make sure folks bumping the si_code
+	 * limits also have to look at this code.  Make sure any
+	 * new fields are handled in copy_siginfo_to_user32()!
+	 */
+	BUILD_BUG_ON(NSIGILL  != 8);
+	BUILD_BUG_ON(NSIGFPE  != 8);
+	BUILD_BUG_ON(NSIGSEGV != 4);
+	BUILD_BUG_ON(NSIGBUS  != 5);
+	BUILD_BUG_ON(NSIGTRAP != 4);
+	BUILD_BUG_ON(NSIGCHLD != 6);
+	BUILD_BUG_ON(NSIGSYS  != 1);
+
+	/* This is part of the ABI and can never change in size: */
+	BUILD_BUG_ON(sizeof(compat_siginfo_t) != 128);
+	/*
+	 * The offsets of all the (unioned) si_fields are fixed
+	 * in the ABI, of course.  Make sure none of them ever
+	 * move and are always at the beginning:
+	 */
+	BUILD_BUG_ON(offsetof(compat_siginfo_t, _sifields) != 3 * sizeof(int));
+#define CHECK_CSI_OFFSET(name)	  BUILD_BUG_ON(_sifields_offset != offsetof(compat_siginfo_t, _sifields.name))
+
+	 /*
+	 * Ensure that the size of each si_field never changes.
+	 * If it does, it is a sign that the
+	 * copy_siginfo_to_user32() code below needs to updated
+	 * along with the size in the CHECK_SI_SIZE().
+	 *
+	 * We repeat this check for both the generic and compat
+	 * siginfos.
+	 *
+	 * Note: it is OK for these to grow as long as the whole
+	 * structure stays within the padding size (checked
+	 * above).
+	 */
+#define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((compat_siginfo_t *)0)->_sifields.name))
+#define CHECK_SI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((siginfo_t *)0)->_sifields.name))
+
+	CHECK_CSI_OFFSET(_kill);
+	CHECK_CSI_SIZE  (_kill, 2*sizeof(int));
+	CHECK_SI_SIZE   (_kill, 2*sizeof(int));
+
+	CHECK_CSI_OFFSET(_timer);
+	CHECK_CSI_SIZE  (_timer, 5*sizeof(int));
+	CHECK_SI_SIZE   (_timer, 6*sizeof(int));
+
+	CHECK_CSI_OFFSET(_rt);
+	CHECK_CSI_SIZE  (_rt, 3*sizeof(int));
+	CHECK_SI_SIZE   (_rt, 4*sizeof(int));
+
+	CHECK_CSI_OFFSET(_sigchld);
+	CHECK_CSI_SIZE  (_sigchld, 5*sizeof(int));
+	CHECK_SI_SIZE   (_sigchld, 8*sizeof(int));
+
+	CHECK_CSI_OFFSET(_sigchld_x32);
+	CHECK_CSI_SIZE  (_sigchld_x32, 7*sizeof(int));
+	/* no _sigchld_x32 in the generic siginfo_t */
+
+	CHECK_CSI_OFFSET(_sigfault);
+	CHECK_CSI_SIZE  (_sigfault, 4*sizeof(int));
+	CHECK_SI_SIZE   (_sigfault, 8*sizeof(int));
+
+	CHECK_CSI_OFFSET(_sigpoll);
+	CHECK_CSI_SIZE  (_sigpoll, 2*sizeof(int));
+	CHECK_SI_SIZE   (_sigpoll, 4*sizeof(int));
+
+	CHECK_CSI_OFFSET(_sigsys);
+	CHECK_CSI_SIZE  (_sigsys, 3*sizeof(int));
+	CHECK_SI_SIZE   (_sigsys, 4*sizeof(int));
+
+	/* any new si_fields should be added here */
+}
+
+void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
+{
+	/* Don't leak in-kernel non-uapi flags to user-space */
+	if (oact)
+		oact->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
+
+	if (!act)
+		return;
+
+	/* Don't let flags to be set from userspace */
+	act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
+
+	if (user_64bit_mode(current_pt_regs()))
+		return;
+
+	if (in_ia32_syscall())
+		act->sa.sa_flags |= SA_IA32_ABI;
+	if (in_x32_syscall())
+		act->sa.sa_flags |= SA_X32_ABI;
+}
+
+int __copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from,
+		bool x32_ABI)
 {
 	int err = 0;
-	bool ia32 = test_thread_flag(TIF_IA32);
+
+	signal_compat_build_tests();
 
 	if (!access_ok(VERIFY_WRITE, to, sizeof(compat_siginfo_t)))
 		return -EFAULT;
@@ -32,13 +147,28 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
 					  &to->_sifields._pad[0]);
 			switch (from->si_code >> 16) {
 			case __SI_FAULT >> 16:
+				if (from->si_signo == SIGBUS &&
+				    (from->si_code == BUS_MCEERR_AR ||
+				     from->si_code == BUS_MCEERR_AO))
+					put_user_ex(from->si_addr_lsb, &to->si_addr_lsb);
+
+				if (from->si_signo == SIGSEGV) {
+					if (from->si_code == SEGV_BNDERR) {
+						compat_uptr_t lower = (unsigned long)&to->si_lower;
+						compat_uptr_t upper = (unsigned long)&to->si_upper;
+						put_user_ex(lower, &to->si_lower);
+						put_user_ex(upper, &to->si_upper);
+					}
+					if (from->si_code == SEGV_PKUERR)
+						put_user_ex(from->si_pkey, &to->si_pkey);
+				}
 				break;
 			case __SI_SYS >> 16:
 				put_user_ex(from->si_syscall, &to->si_syscall);
 				put_user_ex(from->si_arch, &to->si_arch);
 				break;
 			case __SI_CHLD >> 16:
-				if (ia32) {
+				if (!x32_ABI) {
 					put_user_ex(from->si_utime, &to->si_utime);
 					put_user_ex(from->si_stime, &to->si_stime);
 				} else {
@@ -72,6 +202,12 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
 	return err;
 }
 
+/* from syscall's path, where we know the ABI */
+int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
+{
+	return __copy_siginfo_to_user32(to, from, in_x32_syscall());
+}
+
 int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
 {
 	int err = 0;