From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756739Ab3AOKzw (ORCPT ); Tue, 15 Jan 2013 05:55:52 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:53763 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1756216Ab3AOKzn (ORCPT ); Tue, 15 Jan 2013 05:55:43 -0500 X-IronPort-AV: E=Sophos;i="4.84,473,1355068800"; d="scan'208";a="6591339" From: Tang Chen To: akpm@linux-foundation.org, rientjes@google.com, len.brown@intel.com, benh@kernel.crashing.org, paulus@samba.org, cl@linux.com, minchan.kim@gmail.com, kosaki.motohiro@jp.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, wujianguo@huawei.com, wency@cn.fujitsu.com, tangchen@cn.fujitsu.com, hpa@zytor.com, linfeng@cn.fujitsu.com, laijs@cn.fujitsu.com, mgorman@suse.de, yinghai@kernel.org, glommer@parallels.com, jiang.liu@huawei.com Cc: x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-ia64@vger.kernel.org, cmetcalf@tilera.com, sparclinux@vger.kernel.org Subject: [BUG Fix Patch 1/6] Bug fix: Hold spinlock across find|remove /sys/firmware/memmap/X operation. Date: Tue, 15 Jan 2013 18:54:22 +0800 Message-Id: <1358247267-18089-2-git-send-email-tangchen@cn.fujitsu.com> X-Mailer: git-send-email 1.7.10.1 In-Reply-To: <1358247267-18089-1-git-send-email-tangchen@cn.fujitsu.com> References: <1358247267-18089-1-git-send-email-tangchen@cn.fujitsu.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/01/15 18:54:27, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/01/15 18:54:29, Serialize complete at 2013/01/15 18:54:29 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It is unsafe to return an entry pointer and release the map_entries_lock. So we should not hold the map_entries_lock separately in firmware_map_find_entry() and firmware_map_remove_entry(). Hold the map_entries_lock across find and remove /sys/firmware/memmap/X operation. And also, users of these two functions need to be careful to hold the lock when using these two functions. The suggestion is from Andrew Morton Signed-off-by: Tang Chen --- drivers/firmware/memmap.c | 25 +++++++++++++++++-------- 1 files changed, 17 insertions(+), 8 deletions(-) diff --git a/drivers/firmware/memmap.c b/drivers/firmware/memmap.c index 4211da5..940c4e9 100644 --- a/drivers/firmware/memmap.c +++ b/drivers/firmware/memmap.c @@ -150,12 +150,12 @@ static int firmware_map_add_entry(u64 start, u64 end, * firmware_map_remove_entry() - Does the real work to remove a firmware * memmap entry. * @entry: removed entry. + * + * The caller must hold map_entries_lock, and release it properly. **/ static inline void firmware_map_remove_entry(struct firmware_map_entry *entry) { - spin_lock(&map_entries_lock); list_del(&entry->list); - spin_unlock(&map_entries_lock); } /* @@ -188,23 +188,28 @@ static inline void remove_sysfs_fw_map_entry(struct firmware_map_entry *entry) } /* - * Search memmap entry + * firmware_map_find_entry: Search memmap entry. + * @start: Start of the memory range. + * @end: End of the memory range (exclusive). + * @type: Type of the memory range. + * + * This function is to find the memmap entey of a given memory range. + * The caller must hold map_entries_lock, and must not release the lock + * until the processing of the returned entry has completed. + * + * Return pointer to the entry to be found on success, or NULL on failure. */ - static struct firmware_map_entry * __meminit firmware_map_find_entry(u64 start, u64 end, const char *type) { struct firmware_map_entry *entry; - spin_lock(&map_entries_lock); list_for_each_entry(entry, &map_entries, list) if ((entry->start == start) && (entry->end == end) && (!strcmp(entry->type, type))) { - spin_unlock(&map_entries_lock); return entry; } - spin_unlock(&map_entries_lock); return NULL; } @@ -274,11 +279,15 @@ int __meminit firmware_map_remove(u64 start, u64 end, const char *type) { struct firmware_map_entry *entry; + spin_lock(&map_entries_lock); entry = firmware_map_find_entry(start, end - 1, type); - if (!entry) + if (!entry) { + spin_unlock(&map_entries_lock); return -EINVAL; + } firmware_map_remove_entry(entry); + spin_unlock(&map_entries_lock); /* remove the memmap entry */ remove_sysfs_fw_map_entry(entry); -- 1.7.1