signal: Unify and correct copy_siginfo_to_user32

Among the existing architecture specific versions of
copy_siginfo_to_user32 there are several different implementation
problems.  Some architectures fail to handle all of the cases in in
the siginfo union.  Some architectures perform a blind copy of the
siginfo union when the si_code is negative.  A blind copy suggests the
data is expected to be in 32bit siginfo format, which means that
receiving such a signal via signalfd won't work, or that the data is
in 64bit siginfo and the code is copying nonsense to userspace.

Create a single instance of copy_siginfo_to_user32 that all of the
architectures can share, and teach it to handle all of the cases in
the siginfo union correctly, with the assumption that siginfo is
stored internally to the kernel is 64bit siginfo format.

A special case is made for x86 x32 format.  This is needed as presence
of both x32 and ia32 on x86_64 results in two different 32bit signal
formats.  By allowing this small special case there winds up being
exactly one code base that needs to be maintained between all of the
architectures.  Vastly increasing the testing base and the chances of
finding bugs.

As the x86 copy of copy_siginfo_to_user32 the call of the x86
signal_compat_build_tests were moved into sigaction_compat_abi, so
that they will keep running.

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

1 files changed, 90 insertions, 0 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index bebe44265b8b..4976f05aa09b 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2815,6 +2815,96 @@ int copy_siginfo_to_user(siginfo_t __user *to, const siginfo_t *from)
 }
 
 #ifdef CONFIG_COMPAT
+int copy_siginfo_to_user32(struct compat_siginfo __user *to,
+			   const struct siginfo *from)
+#if defined(CONFIG_X86_X32_ABI) || defined(CONFIG_IA32_EMULATION)
+{
+	return __copy_siginfo_to_user32(to, from, in_x32_syscall());
+}
+int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
+			     const struct siginfo *from, bool x32_ABI)
+#endif
+{
+	struct compat_siginfo new;
+	memset(&new, 0, sizeof(new));
+
+	new.si_signo = from->si_signo;
+	new.si_errno = from->si_errno;
+	new.si_code  = from->si_code;
+	switch(siginfo_layout(from->si_signo, from->si_code)) {
+	case SIL_KILL:
+		new.si_pid = from->si_pid;
+		new.si_uid = from->si_uid;
+		break;
+	case SIL_TIMER:
+		new.si_tid     = from->si_tid;
+		new.si_overrun = from->si_overrun;
+		new.si_int     = from->si_int;
+		break;
+	case SIL_POLL:
+		new.si_band = from->si_band;
+		new.si_fd   = from->si_fd;
+		break;
+	case SIL_FAULT:
+		new.si_addr = ptr_to_compat(from->si_addr);
+#ifdef __ARCH_SI_TRAPNO
+		new.si_trapno = from->si_trapno;
+#endif
+#ifdef BUS_MCEERR_AR
+		if ((from->si_signo == SIGBUS) && (from->si_code == BUS_MCEERR_AR))
+			new.si_addr_lsb = from->si_addr_lsb;
+#endif
+#ifdef BUS_MCEERR_AO
+		if ((from->si_signo == SIGBUS) && (from->si_code == BUS_MCEERR_AO))
+			new.si_addr_lsb = from->si_addr_lsb;
+#endif
+#ifdef SEGV_BNDERR
+		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);
+		}
+#endif
+#ifdef SEGV_PKUERR
+		if ((from->si_signo == SIGSEGV) &&
+		    (from->si_code == SEGV_PKUERR))
+			new.si_pkey = from->si_pkey;
+#endif
+
+		break;
+	case SIL_CHLD:
+		new.si_pid    = from->si_pid;
+		new.si_uid    = from->si_uid;
+		new.si_status = from->si_status;
+#ifdef CONFIG_X86_X32_ABI
+		if (x32_ABI) {
+			new._sifields._sigchld_x32._utime = from->si_utime;
+			new._sifields._sigchld_x32._stime = from->si_stime;
+		} else
+#endif
+		{
+			new.si_utime = from->si_utime;
+			new.si_stime = from->si_stime;
+		}
+		break;
+	case SIL_RT:
+		new.si_pid = from->si_pid;
+		new.si_uid = from->si_uid;
+		new.si_int = from->si_int;
+		break;
+	case SIL_SYS:
+		new.si_call_addr = ptr_to_compat(from->si_call_addr);
+		new.si_syscall   = from->si_syscall;
+		new.si_arch      = from->si_arch;
+		break;
+	}
+
+	if (copy_to_user(to, &new, sizeof(struct compat_siginfo)))
+		return -EFAULT;
+
+	return 0;
+}
+
 int copy_siginfo_from_user32(struct siginfo *to,
 			     const struct compat_siginfo __user *ufrom)
 {