From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x2262uI1gL9krO9iUmDSjM+zeXJ1bL0wFgco/3a6CgIj8AsPyJ3T6nQ8eeCWsGaw3v3H2Fk+z ARC-Seal: i=1; a=rsa-sha256; t=1519676203; cv=none; d=google.com; s=arc-20160816; b=mFiEdSmEQDekhb9x+ObV11z6VXnAyX2RAJvy1XnzP2sXAU4gunsquUn/P1KPIyHX+j t/x/jc3cCX+jpu6AgsdeKL2QvGNsMKqZEMKchM8zDREuTmDpCN9XbuWLGyM7g4o9VKn2 brZ015Xk89tvpoPmgL7g32a6px3/4u4Mvx33oLE2yCm+Q8KEte7ELWFxzLSgwdAEozBF B4MD7RLzFYUiGTIyYJWsLS9tHEo+m5jB/jCkdmlD5HfaERxQPLmYx6Imv6eNkuoVyEcL DJq3TwJjxmJrg5lWDPvpDaPNcvpcSbkgK19c7k0YdnsIRqccCSWky6s4nkzSws9qytvT 7pIA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=YPLsfHGIoGJiP86dZoJUZwxf42absXtOS1LNd2rZb4Q=; b=V94dR9FUHYRIR1YtQS3mHSjcteP1SCuRuUunL/LjIBTWDnTo2ht0U7JTOJ/eZIWkYv 2/1ix3I3V32TGDChHcmcWxcTcFpnEQU/D9zNqW0qb9ASJG5zYLGAw7t5CJA0JGA4qx0+ JdafreMQ1z8N7QEZ3/9Q+ChBcgBoxCUPtJrU0jjwJFN96i+U4yiLhapUsdspA3aiaj9/ wDJwS2iWI0iC2+YCrQo4ZY/Hd8NoNxHCKfsyT4z2KGV+Kels5vqgbuOUVWwHkC+jtlME anaHRItd1Y4DAoJ6a100Z0kC1iMqw6oTBbqL1Zb4dQXoyKGqB2EI0X+5zX+XXvGWFpwU Z8HA== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 83.175.124.243 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 83.175.124.243 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alan Stern , Aman Deep , Jeffy Chen Subject: [PATCH 4.4 13/22] usb: ohci: Proper handling of ed_rm_list to handle race condition between usb_kill_urb() and finish_unlinks() Date: Mon, 26 Feb 2018 21:16:13 +0100 Message-Id: <20180226201559.317507165@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180226201558.681421374@linuxfoundation.org> References: <20180226201558.681421374@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1593495994383041854?= X-GMAIL-MSGID: =?utf-8?q?1593495994383041854?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: AMAN DEEP commit 46408ea558df13b110e0866b99624384a33bdeba upstream. There is a race condition between finish_unlinks->finish_urb() function and usb_kill_urb() in ohci controller case. The finish_urb calls spin_unlock(&ohci->lock) before usb_hcd_giveback_urb() function call, then if during this time, usb_kill_urb is called for another endpoint, then new ed will be added to ed_rm_list at beginning for unlink, and ed_rm_list will point to newly added. When finish_urb() is completed in finish_unlinks() and ed->td_list becomes empty as in below code (in finish_unlinks() function): if (list_empty(&ed->td_list)) { *last = ed->ed_next; ed->ed_next = NULL; } else if (ohci->rh_state == OHCI_RH_RUNNING) { *last = ed->ed_next; ed->ed_next = NULL; ed_schedule(ohci, ed); } The *last = ed->ed_next will make ed_rm_list to point to ed->ed_next and previously added ed by usb_kill_urb will be left unreferenced by ed_rm_list. This causes usb_kill_urb() hang forever waiting for finish_unlink to remove added ed from ed_rm_list. The main reason for hang in this race condtion is addition and removal of ed from ed_rm_list in the beginning during usb_kill_urb and later last* is modified in finish_unlinks(). As suggested by Alan Stern, the solution for proper handling of ohci->ed_rm_list is to remove ed from the ed_rm_list before finishing any URBs. Then at the end, we can add ed back to the list if necessary. This properly handle the updated ohci->ed_rm_list in usb_kill_urb(). Fixes: 977dcfdc6031 ("USB: OHCI: don't lose track of EDs when a controller dies") Acked-by: Alan Stern CC: Signed-off-by: Aman Deep Signed-off-by: Jeffy Chen Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ohci-q.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) --- a/drivers/usb/host/ohci-q.c +++ b/drivers/usb/host/ohci-q.c @@ -1018,6 +1018,8 @@ skip_ed: * have modified this list. normally it's just prepending * entries (which we'd ignore), but paranoia won't hurt. */ + *last = ed->ed_next; + ed->ed_next = NULL; modified = 0; /* unlink urbs as requested, but rescan the list after @@ -1076,21 +1078,22 @@ rescan_this: goto rescan_this; /* - * If no TDs are queued, take ED off the ed_rm_list. + * If no TDs are queued, ED is now idle. * Otherwise, if the HC is running, reschedule. - * If not, leave it on the list for further dequeues. + * If the HC isn't running, add ED back to the + * start of the list for later processing. */ if (list_empty(&ed->td_list)) { - *last = ed->ed_next; - ed->ed_next = NULL; ed->state = ED_IDLE; list_del(&ed->in_use_list); } else if (ohci->rh_state == OHCI_RH_RUNNING) { - *last = ed->ed_next; - ed->ed_next = NULL; ed_schedule(ohci, ed); } else { - last = &ed->ed_next; + ed->ed_next = ohci->ed_rm_list; + ohci->ed_rm_list = ed; + /* Don't loop on the same ED */ + if (last == &ohci->ed_rm_list) + last = &ed->ed_next; } if (modified)