Fix compat_sys_sigpending breakage

The latest change of compat_sys_sigpending in commit 8f13621abced
("sigpending(): move compat to native") has broken it in two ways.

First, it tries to write 4 bytes more than userspace expects:
sizeof(old_sigset_t) == sizeof(long) == 8 instead of
sizeof(compat_old_sigset_t) == sizeof(u32) == 4.

Second, on big endian architectures these bytes are being written in the
wrong order.

This bug was found by strace test suite.

Reported-by: Anatoly Pugachev <matorola@gmail.com>
Inspired-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Fixes: 8f13621abced ("sigpending(): move compat to native")
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index caed9133ae52..7e33f8c583e6 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3303,12 +3303,15 @@ SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, set)
 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE1(sigpending, compat_old_sigset_t __user *, set32)
 {
+#ifdef __BIG_ENDIAN
         sigset_t set;
-        int err = do_sigpending(&set, sizeof(old_sigset_t)); 
-        if (err == 0)
-                if (copy_to_user(set32, &set, sizeof(old_sigset_t)))
-                        err = -EFAULT;
+        int err = do_sigpending(&set, sizeof(set.sig[0]));
+        if (!err)
+                err = put_user(set.sig[0], set32);
         return err;
+#else
+        return sys_rt_sigpending((sigset_t __user *)set32, sizeof(*set32));
+#endif
 }
 #endif