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

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...

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/arch/arc/kernel/signal.c b/arch/arc/kernel/signal.c
index 6cb3736..d347bbc 100644 (file)
--- a/arch/arc/kernel/signal.c
+++ b/arch/arc/kernel/signal.c
@@ -107,13 +107,13 @@ static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf)
        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_regs *regs, struct rt_sigframe __user *sf)
        regs->r0        = uregs.scratch.r0;
        regs->sp        = uregs.scratch.sp;
 
-       return err;
+       return 0;
 }
 
 static inline int is_do_ss_needed(unsigned int magic)