From patchwork Thu Jun 14 08:38:09 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lars Persson X-Patchwork-Id: 929297 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-cifs-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=axis.com Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 415xpk4Trgz9s19 for ; Thu, 14 Jun 2018 18:38:22 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754617AbeFNIiV (ORCPT ); Thu, 14 Jun 2018 04:38:21 -0400 Received: from bastet.se.axis.com ([195.60.68.11]:47280 "EHLO bastet.se.axis.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752933AbeFNIiT (ORCPT ); Thu, 14 Jun 2018 04:38:19 -0400 Received: from localhost (localhost [127.0.0.1]) by bastet.se.axis.com (Postfix) with ESMTP id C5153189C2; Thu, 14 Jun 2018 10:38:17 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at bastet.se.axis.com Received: from bastet.se.axis.com ([IPv6:::ffff:127.0.0.1]) by localhost (bastet.se.axis.com [::ffff:127.0.0.1]) (amavisd-new, port 10024) with LMTP id lAX3ESBbCO9e; Thu, 14 Jun 2018 10:38:15 +0200 (CEST) Received: from boulder02.se.axis.com (boulder02.se.axis.com [10.0.8.16]) by bastet.se.axis.com (Postfix) with ESMTPS id D0AD1189B7; Thu, 14 Jun 2018 10:38:15 +0200 (CEST) Received: from boulder02.se.axis.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AE06C1A065; Thu, 14 Jun 2018 10:38:15 +0200 (CEST) Received: from boulder02.se.axis.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A22B71A064; Thu, 14 Jun 2018 10:38:15 +0200 (CEST) Received: from thoth.se.axis.com (unknown [10.0.2.173]) by boulder02.se.axis.com (Postfix) with ESMTP; Thu, 14 Jun 2018 10:38:15 +0200 (CEST) Received: from lnxlarper1.se.axis.com (lnxlarper1.se.axis.com [10.88.41.2]) by thoth.se.axis.com (Postfix) with ESMTP id 9576D2C74; Thu, 14 Jun 2018 10:38:15 +0200 (CEST) Received: by lnxlarper1.se.axis.com (Postfix, from userid 20456) id 8EDF3A4FA1; Thu, 14 Jun 2018 10:38:15 +0200 (CEST) From: Lars Persson To: linux-cifs@vger.kernel.org, sfrench@samba.org Cc: Lars Persson Subject: [PATCH] cifs: Fix use after free of a mid_q_entry Date: Thu, 14 Jun 2018 10:38:09 +0200 Message-Id: <20180614083809.3596-1-larper@axis.com> X-Mailer: git-send-email 2.17.1 X-TM-AS-GCONF: 00 Sender: linux-cifs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org With protocol version 2.0 mounts we have seen crashes with corrupt mid entries. Either the server->pending_mid_q list becomes corrupt with a cyclic reference in one element or a mid object fetched by the demultiplexer thread becomes overwritten during use. Code review identified a race between the demultiplexer thread and the request issuing thread. The demultiplexer thread seems to be written with the assumption that it is the sole user of the mid object until it calls the mid callback which either wakes the issuer task or deletes the mid. This assumption is not true because the issuer task can be woken up earlier by a signal. If the demultiplexer thread has proceeded as far as setting the mid_state to MID_RESPONSE_RECEIVED then the issuer thread will happily end up calling cifs_delete_mid while the demultiplexer thread still is using the mid object. Inserting a delay in the cifs demultiplexer thread widens the race window and makes reproduction of the race very easy: if (server->large_buf) buf = server->bigbuf; + usleep_range(500, 4000); server->lstrp = jiffies; To resolve this I think the proper solution involves putting a reference count on the mid object. This patch makes sure that the demultiplexer thread holds a reference until it has finished processing the transaction. Signed-off-by: Lars Persson Reviewed-by: Pavel Shilovsky --- fs/cifs/cifsglob.h | 1 + fs/cifs/cifsproto.h | 1 + fs/cifs/connect.c | 7 ++++++- fs/cifs/smb1ops.c | 1 + fs/cifs/smb2ops.c | 1 + fs/cifs/smb2transport.c | 1 + fs/cifs/transport.c | 18 +++++++++++++++++- 7 files changed, 28 insertions(+), 2 deletions(-) diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index cb950a5fa078..c7ee09d9a236 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -1362,6 +1362,7 @@ typedef int (mid_handle_t)(struct TCP_Server_Info *server, /* one of these for every pending CIFS request to the server */ struct mid_q_entry { struct list_head qhead; /* mids waiting on reply from this server */ + struct kref refcount; struct TCP_Server_Info *server; /* server corresponding to this mid */ __u64 mid; /* multiplex id */ __u32 pid; /* process id */ diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h index 365a414a75e9..c4e5c69810f9 100644 --- a/fs/cifs/cifsproto.h +++ b/fs/cifs/cifsproto.h @@ -76,6 +76,7 @@ extern struct mid_q_entry *AllocMidQEntry(const struct smb_hdr *smb_buffer, struct TCP_Server_Info *server); extern void DeleteMidQEntry(struct mid_q_entry *midEntry); extern void cifs_delete_mid(struct mid_q_entry *mid); +extern void cifs_mid_q_entry_release(struct mid_q_entry *midEntry); extern void cifs_wake_up_task(struct mid_q_entry *mid); extern int cifs_handle_standard(struct TCP_Server_Info *server, struct mid_q_entry *mid); diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 7a10a5d0731f..90cedf6b3228 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -920,8 +920,11 @@ cifs_demultiplex_thread(void *p) length = mid_entry->receive(server, mid_entry); } - if (length < 0) + if (length < 0) { + if (mid_entry) + cifs_mid_q_entry_release(mid_entry); continue; + } if (server->large_buf) buf = server->bigbuf; @@ -938,6 +941,8 @@ cifs_demultiplex_thread(void *p) if (!mid_entry->multiRsp || mid_entry->multiEnd) mid_entry->callback(mid_entry); + + cifs_mid_q_entry_release(mid_entry); } else if (server->ops->is_oplock_break && server->ops->is_oplock_break(buf, server)) { cifs_dbg(FYI, "Received oplock break\n"); diff --git a/fs/cifs/smb1ops.c b/fs/cifs/smb1ops.c index aff8ce8ba34d..646dcd149de1 100644 --- a/fs/cifs/smb1ops.c +++ b/fs/cifs/smb1ops.c @@ -107,6 +107,7 @@ cifs_find_mid(struct TCP_Server_Info *server, char *buffer) if (compare_mid(mid->mid, buf) && mid->mid_state == MID_REQUEST_SUBMITTED && le16_to_cpu(mid->command) == buf->Command) { + kref_get(&mid->refcount); spin_unlock(&GlobalMid_Lock); return mid; } diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c index 9c6d95ffca97..ba0bc31786d1 100644 --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -203,6 +203,7 @@ smb2_find_mid(struct TCP_Server_Info *server, char *buf) if ((mid->mid == wire_mid) && (mid->mid_state == MID_REQUEST_SUBMITTED) && (mid->command == shdr->Command)) { + kref_get(&mid->refcount); spin_unlock(&GlobalMid_Lock); return mid; } diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c index 8806f3f76c1d..97f24d82ae6b 100644 --- a/fs/cifs/smb2transport.c +++ b/fs/cifs/smb2transport.c @@ -548,6 +548,7 @@ smb2_mid_entry_alloc(const struct smb2_sync_hdr *shdr, temp = mempool_alloc(cifs_mid_poolp, GFP_NOFS); memset(temp, 0, sizeof(struct mid_q_entry)); + kref_init(&temp->refcount); temp->mid = le64_to_cpu(shdr->MessageId); temp->pid = current->pid; temp->command = shdr->Command; /* Always LE */ diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c index 927226a2122f..60faf2fcec7f 100644 --- a/fs/cifs/transport.c +++ b/fs/cifs/transport.c @@ -61,6 +61,7 @@ AllocMidQEntry(const struct smb_hdr *smb_buffer, struct TCP_Server_Info *server) temp = mempool_alloc(cifs_mid_poolp, GFP_NOFS); memset(temp, 0, sizeof(struct mid_q_entry)); + kref_init(&temp->refcount); temp->mid = get_mid(smb_buffer); temp->pid = current->pid; temp->command = cpu_to_le16(smb_buffer->Command); @@ -82,6 +83,21 @@ AllocMidQEntry(const struct smb_hdr *smb_buffer, struct TCP_Server_Info *server) return temp; } +static void _cifs_mid_q_entry_release(struct kref *refcount) +{ + struct mid_q_entry *mid = container_of(refcount, struct mid_q_entry, + refcount); + + mempool_free(mid, cifs_mid_poolp); +} + +void cifs_mid_q_entry_release(struct mid_q_entry *midEntry) +{ + spin_lock(&GlobalMid_Lock); + kref_put(&midEntry->refcount, _cifs_mid_q_entry_release); + spin_unlock(&GlobalMid_Lock); +} + void DeleteMidQEntry(struct mid_q_entry *midEntry) { @@ -110,7 +126,7 @@ DeleteMidQEntry(struct mid_q_entry *midEntry) } } #endif - mempool_free(midEntry, cifs_mid_poolp); + cifs_mid_q_entry_release(midEntry); } void