Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751988Ab3CALBK (ORCPT ); Fri, 1 Mar 2013 06:01:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59235 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751132Ab3CALBI (ORCPT ); Fri, 1 Mar 2013 06:01:08 -0500 Date: Fri, 1 Mar 2013 12:00:43 +0100 From: Anton Arapov To: Ananth N Mavinakayanahalli Cc: Oleg Nesterov , Srikar Dronamraju , LKML , Josh Stone , Frank Eigler , Peter Zijlstra , Ingo Molnar Subject: Re: [RFC PATCH v3 2/6] uretprobes/x86: hijack return address Message-ID: <20130301110043.GA15426@bandura.brq.redhat.com> References: <1362049215-5780-1-git-send-email-anton@redhat.com> <1362049215-5780-3-git-send-email-anton@redhat.com> <20130301054536.GB30500@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130301054536.GB30500@in.ibm.com> X-PGP-Key: http://people.redhat.com/aarapov/gpg User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2748 Lines: 63 On Fri, Mar 01, 2013 at 11:15:36AM +0530, Ananth N Mavinakayanahalli wrote: > On Thu, Feb 28, 2013 at 12:00:11PM +0100, Anton Arapov wrote: > > hijack the return address and replace it with a "trampoline" > > > > v2: > > - remove ->doomed flag, kill task immediately > > > > Signed-off-by: Anton Arapov > > --- > > arch/x86/include/asm/uprobes.h | 1 + > > arch/x86/kernel/uprobes.c | 29 +++++++++++++++++++++++++++++ > > 2 files changed, 30 insertions(+) > > > > diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h > > index 8ff8be7..c353555 100644 > > --- a/arch/x86/include/asm/uprobes.h > > +++ b/arch/x86/include/asm/uprobes.h > > @@ -55,4 +55,5 @@ extern int arch_uprobe_post_xol(struct arch_uprobe *aup, struct pt_regs *regs); > > extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk); > > extern int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data); > > extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs); > > +extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long rp_trampoline_vaddr, struct pt_regs *regs); > > #endif /* _ASM_UPROBES_H */ > > diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c > > index 0ba4cfb..85e2153 100644 > > --- a/arch/x86/kernel/uprobes.c > > +++ b/arch/x86/kernel/uprobes.c > > @@ -697,3 +697,32 @@ bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) > > send_sig(SIGTRAP, current, 0); > > return ret; > > } > > + > > +extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long > > + rp_trampoline_vaddr, struct pt_regs *regs) > > +{ > > + int rasize, ncopied; > > + unsigned long orig_ret_vaddr = 0; /* clear high bits for 32-bit apps */ > > + > > + rasize = is_ia32_task() ? 4 : 8; > > + ncopied = copy_from_user(&orig_ret_vaddr, (void __user *)regs->sp, rasize); > > + if (unlikely(ncopied)) > > What if ncopied < rasize? Agreed that the upper order bits can be 0, but should > you not validate ncopied == rasize? Function returns 0 in case copy_from_user() was not able to copy return address entirely, and "if (ncopied)" makes sure of it. We can't continue if we have no correct return address. copy_from_user() returns number of bytes that were *not* copied, thus "ncopied == rasize" means copy_from_user() was not able to copy *all* bytes. I don't see the point of such check here. Or am I missing anything? thank you! Anton. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/