From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751389AbbCGPkw (ORCPT ); Sat, 7 Mar 2015 10:40:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34802 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751252AbbCGPku (ORCPT ); Sat, 7 Mar 2015 10:40:50 -0500 Date: Sat, 7 Mar 2015 16:38:44 +0100 From: Oleg Nesterov To: Dave Hansen , Borislav Petkov , Ingo Molnar Cc: Andy Lutomirski , Linus Torvalds , Pekka Riikonen , Rik van Riel , Suresh Siddha , LKML , "Yu, Fenghua" , Quentin Casasnovas Subject: [PATCH 1/1] x86/fpu: x86/fpu: avoid math_state_restore() without used_math() in __restore_xstate_sig() Message-ID: <20150307153844.GB25954@redhat.com> References: <54F74F59.5070107@intel.com> <20150305195127.GA12657@redhat.com> <20150307153824.GA25954@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150307153824.GA25954@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 trgiggers BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:41 [] dump_stack+0x59/0xa0 [] ___might_sleep+0x105/0x110 [] ? _raw_spin_unlock_irqrestore+0x3d/0x70 [] __might_sleep+0x7d/0xb0 [] down_read+0x26/0xa0 [] ? _raw_spin_unlock_irqrestore+0x5a/0x70 [] print_vma_addr+0x58/0x130 [] signal_fault+0xbe/0xf0 [] sys32_rt_sigreturn+0xba/0xd0 Change __restore_xstate_sig() to call set_used_math() unconditionally, this avoids sti/cli 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 Cc: --- arch/x86/kernel/xsave.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c index de9dcf8..dff0ec2 100644 --- a/arch/x86/kernel/xsave.c +++ b/arch/x86/kernel/xsave.c @@ -378,7 +378,7 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size) * 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 *buf, void __user *buf_fx, int size) */ 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(); -- 1.5.5.1