Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933111AbbGUPbV (ORCPT ); Tue, 21 Jul 2015 11:31:21 -0400 Received: from cantor2.suse.de ([195.135.220.15]:46958 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932257AbbGUPbU (ORCPT ); Tue, 21 Jul 2015 11:31:20 -0400 Date: Tue, 21 Jul 2015 17:31:07 +0200 From: Borislav Petkov To: Pan Xinhui Cc: "linux-kernel@vger.kernel.org" , tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, toshi.kani@hp.com, jgross@suse.com, mcgrof@suse.com, "mnipxh@163.com" Subject: Re: [PATCH] x86/mm/pat: Do a small optimization in reserve_memtype Message-ID: <20150721153107.GD7434@nazgul.tnic> References: <55ADE6CF.4020200@intel.com> <20150721065555.GB520@nazgul.tnic> <55ADF5A2.1020005@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <55ADF5A2.1020005@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1464 Lines: 42 On Tue, Jul 21, 2015 at 03:32:50PM +0800, Pan Xinhui wrote: > yes, we may access an freed memory at that time. Because entry is > stored in rb-tree. Need lock when we access it. Ah, we touch entry, right. > > improve the comments over memtype_lock to explain what exactly it protects. > > > lock is needed when we access the data stored in rb-tree. :) I didn't ask you what it protects - I can do my own grepping and read pat_rbtree.c just fine - I asked you to update the comment. > I find another bug, although it's very hard to hit. > just in reserve_memtype() > ---------------------------------- > err = rbt_memtype_check_insert(new, new_type); > if (err) { > printk(KERN_INFO "reserve_memtype failed [mem %#010Lx-%#010Lx], track %s, req %s\n", > start, end - 1, > cattr_name(new->type), cattr_name(req_type)); > kfree(new); > spin_unlock(&memtype_lock); > > return err; > } > > spin_unlock(&memtype_lock); //this unlock may cause problems because the next dprintk access *new* Yes. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- 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/