From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751763AbdFILCr (ORCPT ); Fri, 9 Jun 2017 07:02:47 -0400 Received: from mx2.suse.de ([195.135.220.15]:45572 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751676AbdFILCn (ORCPT ); Fri, 9 Jun 2017 07:02:43 -0400 Date: Fri, 9 Jun 2017 13:02:30 +0200 From: Borislav Petkov To: Ricardo Neri Cc: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Andrew Morton , Brian Gerst , Chris Metcalf , Dave Hansen , Paolo Bonzini , Masami Hiramatsu , Huang Rui , Jiri Slaby , Jonathan Corbet , "Michael S. Tsirkin" , Paul Gortmaker , Vlastimil Babka , Chen Yucong , Alexandre Julliard , Stas Sergeev , Fenghua Yu , "Ravi V. Shankar" , Shuah Khan , linux-kernel@vger.kernel.org, x86@kernel.org, linux-msdos@vger.kernel.org, wine-devel@winehq.org, Tony Luck Subject: Re: [PATCH v7 22/26] x86/umip: Force a page fault when unable to copy emulated result to user Message-ID: <20170609110230.rjmce4ifqr5vddac@pd.tnic> References: <20170505181724.55000-1-ricardo.neri-calderon@linux.intel.com> <20170505181724.55000-23-ricardo.neri-calderon@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170505181724.55000-23-ricardo.neri-calderon@linux.intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 05, 2017 at 11:17:20AM -0700, Ricardo Neri wrote: > fixup_umip_exception() will be called from do_general_protection. If the ^ | Please end function names with parentheses. ---+ > former returns false, the latter will issue a SIGSEGV with SEND_SIG_PRIV. > However, when emulation is successful but the emulated result cannot be > copied to user space memory, it is more accurate to issue a SIGSEGV with > SEGV_MAPERR with the offending address. > A new function is inspired in That reads funny. > force_sig_info_fault is introduced to model the page fault. > > Cc: Andy Lutomirski > Cc: Andrew Morton > Cc: H. Peter Anvin > Cc: Borislav Petkov > Cc: Brian Gerst > Cc: Chen Yucong > Cc: Chris Metcalf > Cc: Dave Hansen > Cc: Fenghua Yu > Cc: Huang Rui > Cc: Jiri Slaby > Cc: Jonathan Corbet > Cc: Michael S. Tsirkin > Cc: Paul Gortmaker > Cc: Peter Zijlstra > Cc: Ravi V. Shankar > Cc: Shuah Khan > Cc: Vlastimil Babka > Cc: Tony Luck > Cc: Paolo Bonzini > Cc: Liang Z. Li > Cc: Alexandre Julliard > Cc: Stas Sergeev > Cc: x86@kernel.org > Cc: linux-msdos@vger.kernel.org > Signed-off-by: Ricardo Neri > --- > arch/x86/kernel/umip.c | 45 +++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 43 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c > index c7c5795..ff7366a 100644 > --- a/arch/x86/kernel/umip.c > +++ b/arch/x86/kernel/umip.c > @@ -148,6 +148,41 @@ static int __emulate_umip_insn(struct insn *insn, enum umip_insn umip_inst, > } > > /** > + * __force_sig_info_umip_fault() - Force a SIGSEGV with SEGV_MAPERR > + * @address: Address that caused the signal > + * @regs: Register set containing the instruction pointer > + * > + * Force a SIGSEGV signal with SEGV_MAPERR as the error code. This function is > + * intended to be used to provide a segmentation fault when the result of the > + * UMIP emulation could not be copied to the user space memory. > + * > + * Return: none > + */ > +static void __force_sig_info_umip_fault(void __user *address, > + struct pt_regs *regs) > +{ > + siginfo_t info; > + struct task_struct *tsk = current; > + > + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV)) { Save an indentation level: if (!(show_unhandled_signals && unhandled_signal(tsk, SIGSEGV))) return; printk... > + printk_ratelimited("%s[%d] umip emulation segfault ip:%lx sp:%lx error:%x in %lx\n", > + tsk->comm, task_pid_nr(tsk), regs->ip, > + regs->sp, X86_PF_USER | X86_PF_WRITE, > + regs->ip); > + } > + > + tsk->thread.cr2 = (unsigned long)address; > + tsk->thread.error_code = X86_PF_USER | X86_PF_WRITE; > + tsk->thread.trap_nr = X86_TRAP_PF; > + > + info.si_signo = SIGSEGV; > + info.si_errno = 0; > + info.si_code = SEGV_MAPERR; > + info.si_addr = address; > + force_sig_info(SIGSEGV, &info, tsk); > +} > + > +/** > * fixup_umip_exception() - Fixup #GP faults caused by UMIP > * @regs: Registers as saved when entering the #GP trap > * > @@ -235,8 +270,14 @@ bool fixup_umip_exception(struct pt_regs *regs) > if ((unsigned long)uaddr == -1L) > return false; > nr_copied = copy_to_user(uaddr, dummy_data, dummy_data_size); > - if (nr_copied > 0) > - return false; > + if (nr_copied > 0) { > + /* > + * If copy fails, send a signal and tell caller that > + * fault was fixed up Pls end sentences in the comments with a fullstop. > + */ > + __force_sig_info_umip_fault(uaddr, regs); > + return true; > + } > } > > /* increase IP to let the program keep going */ > -- > 2.9.3 > -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --