[PATCH 4.8 090/140] arc: dont leak bits of kernel stack into coredump

From: Greg Kroah-Hartman
Date: Wed Oct 26 2016 - 09:19:29 EST


4.8-stable review patch. If anyone has any objections, please let me know.

------------------

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
arch/arc/kernel/signal.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/arc/kernel/signal.c
+++ b/arch/arc/kernel/signal.c
@@ -107,13 +107,13 @@ static int restore_usr_regs(struct pt_re
struct user_regs_struct uregs;

err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
- if (!err)
- set_current_blocked(&set);
-
err |= __copy_from_user(&uregs.scratch,
&(sf->uc.uc_mcontext.regs.scratch),
sizeof(sf->uc.uc_mcontext.regs.scratch));
+ if (err)
+ return err;

+ set_current_blocked(&set);
regs->bta = uregs.scratch.bta;
regs->lp_start = uregs.scratch.lp_start;
regs->lp_end = uregs.scratch.lp_end;
@@ -138,7 +138,7 @@ static int restore_usr_regs(struct pt_re
regs->r0 = uregs.scratch.r0;
regs->sp = uregs.scratch.sp;

- return err;
+ return 0;
}

static inline int is_do_ss_needed(unsigned int magic)