arc: don't leak bits of kernel stack into coredump

commit 7798bf2140ebcc36eafec6a4194fffd8d585d471 upstream.

On faulting sigreturn we do get SIGSEGV, all right, but anything
we'd put into pt_regs could end up in the coredump.  And since
__copy_from_user() never zeroed on arc, we'd better bugger off
on its failure without copying random uninitialized bits of
kernel stack into pt_regs...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[bwh: Backported to 3.16:
 - Adjust context
 - Don't change the single return statement]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/arc/kernel/signal.c b/arch/arc/kernel/signal.c
index a0c63fc48457db4aa58d58a674a7e0568db0b46f..0943ff84f28fbab83f8a0dc1f8075cf60d15800f 100644 (file)
--- a/arch/arc/kernel/signal.c
+++ b/arch/arc/kernel/signal.c
@@ -80,11 +80,12 @@ static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf)
        int err;
 
        err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
-       if (!err)
-               set_current_blocked(&set);
-
        err |= __copy_from_user(regs, &(sf->uc.uc_mcontext.regs.scratch),
                                sizeof(sf->uc.uc_mcontext.regs.scratch));
+       if (err)
+               return err;
+
+       set_current_blocked(&set);
 
        return err;
 }