From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: [PATCH] ses: Fix racy cleanup of /sys in remove_dev() Date: Thu, 24 Aug 2017 15:13:52 +0200 Message-ID: <1503580432-105307-1-git-send-email-hare@suse.de> Return-path: Received: from mx2.suse.de ([195.135.220.15]:42760 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751349AbdHXNN4 (ORCPT ); Thu, 24 Aug 2017 09:13:56 -0400 Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "Martin K. Petersen" Cc: Christoph Hellwig , James Bottomley , linux-scsi@vger.kernel.org, Calvin Owens From: Calvin Owens Currently we free the resources backing the enclosure device before we call device_unregister(). This is racy: during rmmod of low-level SCSI drivers that hook into enclosure, we end up with a small window of time during which writing to /sys can OOPS. Example trace with mpt3sas: general protection fault: 0000 [#1] SMP KASAN Modules linked in: mpt3sas(-) <...> RIP: [] ses_get_page2_descriptor.isra.6+0x38/0x220 [ses] Call Trace: [] ses_set_fault+0xf4/0x400 [ses] [] set_component_fault+0xa9/0xf0 [enclosure] [] dev_attr_store+0x3c/0x70 [] sysfs_kf_write+0x115/0x180 [] kernfs_fop_write+0x275/0x3a0 [] __vfs_write+0xe0/0x3e0 [] vfs_write+0x13f/0x4a0 [] SyS_write+0x111/0x230 [] entry_SYSCALL_64_fastpath+0x13/0x94 Fortunately the solution is extremely simple: call device_unregister() before we free the resources, and the race no longer exists. The driver core holds a reference over ->remove_dev(), so AFAICT this is safe. Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=989094 Signed-off-by: Calvin Owens Acked-by: Hannes Reinecke --- drivers/scsi/ses.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/scsi/ses.c b/drivers/scsi/ses.c index a3f9350..ea7066c 100644 --- a/drivers/scsi/ses.c +++ b/drivers/scsi/ses.c @@ -818,8 +818,6 @@ static void ses_intf_remove_enclosure(struct scsi_device *sdev) if (!edev) return; - enclosure_unregister(edev); - ses_dev = edev->scratch; edev->scratch = NULL; @@ -831,6 +829,7 @@ static void ses_intf_remove_enclosure(struct scsi_device *sdev) kfree(edev->component[0].scratch); put_device(&edev->edev); + enclosure_unregister(edev); } static void ses_intf_remove(struct device *cdev, -- 1.8.5.6