kernel-wide: fix missing validations on __get/__put/__copy_to/__copy_from_user()

I found the following pattern that leads in to interesting findings:

  grep -r "ret.*|=.*__put_user" *
  grep -r "ret.*|=.*__get_user" *
  grep -r "ret.*|=.*__copy" *

The __put_user() calls in compat_ioctl.c, ptrace compat, signal compat,
since those appear in compat code, we could probably expect the kernel
addresses not to be reachable in the lower 32-bit range, so I think they
might not be exploitable.

For the "__get_user" cases, I don't think those are exploitable: the worse
that can happen is that the kernel will copy kernel memory into in-kernel
buffers, and will fail immediately afterward.

The alpha csum_partial_copy_from_user() seems to be missing the
access_ok() check entirely.  The fix is inspired from x86.  This could
lead to information leak on alpha.  I also noticed that many architectures
map csum_partial_copy_from_user() to csum_partial_copy_generic(), but I
wonder if the latter is performing the access checks on every
architectures.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

diff --git a/kernel/signal.c b/kernel/signal.c
index 50e4107..ded28b9 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3394,7 +3394,7 @@
 		new_ka.sa.sa_restorer = compat_ptr(restorer);
 #endif
 		ret |= copy_from_user(&mask, &act->sa_mask, sizeof(mask));
-		ret |= __get_user(new_ka.sa.sa_flags, &act->sa_flags);
+		ret |= get_user(new_ka.sa.sa_flags, &act->sa_flags);
 		if (ret)
 			return -EFAULT;
 		sigset_from_compat(&new_ka.sa.sa_mask, &mask);
@@ -3406,7 +3406,7 @@
 		ret = put_user(ptr_to_compat(old_ka.sa.sa_handler), 
 			       &oact->sa_handler);
 		ret |= copy_to_user(&oact->sa_mask, &mask, sizeof(mask));
-		ret |= __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
+		ret |= put_user(old_ka.sa.sa_flags, &oact->sa_flags);
 #ifdef __ARCH_HAS_SA_RESTORER
 		ret |= put_user(ptr_to_compat(old_ka.sa.sa_restorer),
 				&oact->sa_restorer);