From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Trofimovich Date: Thu, 01 Apr 2021 06:28:46 +0000 Subject: Re: [PATCH] ia64: fix user_stack_pointer() for ptrace() Message-Id: <20210401072846.0cabee26@sf> List-Id: References: <20210331084447.2561532-1-slyfox@gentoo.org> <20210331174908.4655f2a41a7b1bbec36fae47@linux-foundation.org> In-Reply-To: <20210331174908.4655f2a41a7b1bbec36fae47@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Oleg Nesterov , linux-ia64@vger.kernel.org, "Dmitry V . Levin" On Wed, 31 Mar 2021 17:49:08 -0700 Andrew Morton wrote: > On Wed, 31 Mar 2021 09:44:47 +0100 Sergei Trofimovich wrote: > > > ia64 has two stacks: > > - memory stack (or stack), pointed at by by r12 > > - register backing store (register stack), pointed at > > ar.bsp/ar.bspstore with complications around dirty > > register frame on CPU. > > > > In https://bugs.gentoo.org/769614 Dmitry noticed that > > PTRACE_GET_SYSCALL_INFO returns register stack instead > > memory stack. > > > > The bug comes from the fact that user_stack_pointer() and > > current_user_stack_pointer() don't return the same register: > > > > ulong user_stack_pointer(struct pt_regs *regs) { return regs->ar_bspstore; } > > #define current_user_stack_pointer() (current_pt_regs()->r12) > > > > The change gets both back in sync. > > > > I think ptrace(PTRACE_GET_SYSCALL_INFO) is the only affected user > > by this bug on ia64. > > > > The change fixes 'rt_sigreturn.gen.test' strace test where > > it was observed initially. > > > > I assume a cc:stable is justified here? > > The bug seems to have been there for 10+ years, so there isn't a lot of > point in looking for the Fixes: reference. Yes, I think cc:stable is fine. -- Sergei