From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=192.55.52.120; helo=mga04.intel.com; envelope-from=hao.a.wu@intel.com; receiver=edk2-devel@lists.01.org Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 2B8BD22590E37 for ; Mon, 16 Apr 2018 22:04:26 -0700 (PDT) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Apr 2018 22:04:25 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.48,462,1517904000"; d="scan'208";a="34201954" Received: from shwdeopenpsi014.ccr.corp.intel.com ([10.239.9.10]) by orsmga008.jf.intel.com with ESMTP; 16 Apr 2018 22:04:24 -0700 From: Hao Wu To: edk2-devel@lists.01.org Cc: Hao Wu , Ruiyu Ni Date: Tue, 17 Apr 2018 13:04:21 +0800 Message-Id: <20180417050421.43036-1-hao.a.wu@intel.com> X-Mailer: git-send-email 2.12.0.windows.1 Subject: [PATCH] FatPkg/EnhancedFatDxe: Ensure traverse of subtasks is delete-safe X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 17 Apr 2018 05:04:26 -0000 Within function FatQueueTask(), the traverse of FAT subtasks for executing the disk read/write is not delete-safe. For the below case: FatDiskIo(): When non-blocking access, creates subtasks and creates event (FatOnAccessComplete, NOTIFY level) when subtasks finish. FatQueueTask(): Traverses the subtasks and submits them one by one at Tpl lower than NOTIFY. Disk R/W completes really quick. FatOnAccessComplete(): Removes the finished subtask, causing the traverse in FatQueueTask() broken. This commits will refine the subtask traverse in FatQueueTask() to be delete-safe. Cc: Ruiyu Ni Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu Reviewed-by: Ruiyu Ni --- FatPkg/EnhancedFatDxe/Misc.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/FatPkg/EnhancedFatDxe/Misc.c b/FatPkg/EnhancedFatDxe/Misc.c index c035670bf7..af66b1d0e3 100644 --- a/FatPkg/EnhancedFatDxe/Misc.c +++ b/FatPkg/EnhancedFatDxe/Misc.c @@ -132,6 +132,7 @@ FatQueueTask ( { EFI_STATUS Status; LIST_ENTRY *Link; + LIST_ENTRY *NextLink; FAT_SUBTASK *Subtask; // @@ -149,9 +150,17 @@ FatQueueTask ( EfiReleaseLock (&FatTaskLock); Status = EFI_SUCCESS; - for ( Link = GetFirstNode (&Task->Subtasks) - ; !IsNull (&Task->Subtasks, Link) - ; Link = GetNextNode (&Task->Subtasks, Link) + // + // Use NextLink to store the next link of the list, because Link might be remove from the + // doubly-linked list and get freed in the end of current loop. + // + // Also, list operation APIs like IsNull() and GetNextNode() are avoided during the loop, since + // they may check the validity of doubly-linked lists by traversing them. These APIs cannot + // handle list elements being removed during the traverse. + // + for ( Link = GetFirstNode (&Task->Subtasks), NextLink = GetNextNode (&Task->Subtasks, Link) + ; Link != &Task->Subtasks + ; Link = NextLink, NextLink = Link->ForwardLink ) { Subtask = CR (Link, FAT_SUBTASK, Link, FAT_SUBTASK_SIGNATURE); if (Subtask->Write) { -- 2.12.0.windows.1