[PATCH 3.16 047/306] arc: don't leak bits of kernel stack into coredump

Ben Hutchings
2017-02-15T23:36:08Z

From: Al Viro <viro@zeniv.linux.org.uk>

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>
---
arch/arc/kernel/signal.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/arch/arc/kernel/signal.c
+++ b/arch/arc/kernel/signal.c
@@ -80,11 +80,12 @@ static int restore_usr_regs(struct pt_re
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;
}