From e120dcb6b2a11840b08f0fc0d2e90256b7b6e842 Mon Sep 17 00:00:00 2001 From: Calvin Owens Date: Fri, 13 May 2016 13:28:21 -0700 Subject: [PATCH] ses: Fix racy cleanup of /sys in remove_dev() 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. Signed-off-by: Calvin Owens Reviewed-by: James Bottomley Signed-off-by: Martin K. Petersen --- drivers/scsi/ses.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/ses.c b/drivers/scsi/ses.c index 53ef1cb6418e..0e8601aa877a 100644 --- a/drivers/scsi/ses.c +++ b/drivers/scsi/ses.c @@ -778,6 +778,8 @@ static void ses_intf_remove_enclosure(struct scsi_device *sdev) if (!edev) return; + enclosure_unregister(edev); + ses_dev = edev->scratch; edev->scratch = NULL; @@ -789,7 +791,6 @@ 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,