From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755050AbbCXRTY (ORCPT ); Tue, 24 Mar 2015 13:19:24 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33872 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754310AbbCXRII (ORCPT ); Tue, 24 Mar 2015 13:08:08 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Oleg Nesterov , Borislav Petkov , Andy Lutomirski , Borislav Petkov , Dave Hansen , Fenghua Yu , "H. Peter Anvin" , Linus Torvalds , Pekka Riikonen , Quentin Casasnovas , Rik van Riel , Suresh Siddha , Thomas Gleixner , Ingo Molnar Subject: [PATCH 3.19 098/123] x86/fpu: Avoid math_state_restore() without used_math() in __restore_xstate_sig() Date: Tue, 24 Mar 2015 16:46:47 +0100 Message-Id: <20150324154428.428513491@linuxfoundation.org> X-Mailer: git-send-email 2.3.3 In-Reply-To: <20150324154423.655554012@linuxfoundation.org> References: <20150324154423.655554012@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov commit a7c80ebcac3068b1c3cb27d538d29558c30010c8 upstream. math_state_restore() assumes it is called with irqs disabled, but this is not true if the caller is __restore_xstate_sig(). This means that if ia32_fxstate == T and __copy_from_user() fails, __restore_xstate_sig() returns with irqs disabled too. This triggers: BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:41 dump_stack ___might_sleep ? _raw_spin_unlock_irqrestore __might_sleep down_read ? _raw_spin_unlock_irqrestore print_vma_addr signal_fault sys32_rt_sigreturn Change __restore_xstate_sig() to call set_used_math() unconditionally. This avoids enabling and disabling interrupts in math_state_restore(). If copy_from_user() fails, we can simply do fpu_finit() by hand. [ Note: this is only the first step. math_state_restore() should not check used_math(), it should set this flag. While init_fpu() should simply die. ] Signed-off-by: Oleg Nesterov Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Pekka Riikonen Cc: Quentin Casasnovas Cc: Rik van Riel Cc: Suresh Siddha Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20150307153844.GB25954@redhat.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/xsave.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/arch/x86/kernel/xsave.c +++ b/arch/x86/kernel/xsave.c @@ -378,7 +378,7 @@ int __restore_xstate_sig(void __user *bu * thread's fpu state, reconstruct fxstate from the fsave * header. Sanitize the copied state etc. */ - struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave; + struct fpu *fpu = &tsk->thread.fpu; struct user_i387_ia32_struct env; int err = 0; @@ -392,14 +392,15 @@ int __restore_xstate_sig(void __user *bu */ drop_fpu(tsk); - if (__copy_from_user(xsave, buf_fx, state_size) || + if (__copy_from_user(&fpu->state->xsave, buf_fx, state_size) || __copy_from_user(&env, buf, sizeof(env))) { + fpu_finit(fpu); err = -1; } else { sanitize_restored_xstate(tsk, &env, xstate_bv, fx_only); - set_used_math(); } + set_used_math(); if (use_eager_fpu()) { preempt_disable(); math_state_restore();