From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x226wdrxqfKfM04OAavf7J6NtGw8A7LGANyRkfk2Q+C3JIZeTc1qV7fW6y4B18jZAZVNZqrEs ARC-Seal: i=1; a=rsa-sha256; t=1519676959; cv=none; d=google.com; s=arc-20160816; b=DYiJCc86g+jCn1Q+h/QEl2Nanb2vVEaChVPA7XLZavB438Z6QNKrz2cqstwro3zZaj EWdMuB1+aICG6bwW6RNElSqhgH4dF+bUR0C3Lw8qgDXL7vF60MHRcJ+rhrVJ839SK1UY tiKYdTN1fXKLVlcQsCgjmjzD4Gsm+kv66/q4eDhsN1HEI1d4D56mEmZElAyj7FFSj/py u2mGMYos/tgzlxhedQT/QCvXT4aLTnJXuFNFCj8kU/9b+GUz3C+0FFV5p4WU0wY1nSg3 /LGRZrOjVQkjT1RFOH3xlRTfzVLabqoG6KvEhbha4wtp7izlRDUn/J4Qism5WpLD+0+s BJxw== 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=Snua8oiQao0wbfTOGjx5ax24nVBhe2cEU1Z4JqBbiNk=; b=IR73kM11IPuLcplsBB4afMgXpm0Woyikpn7X0+5YsWNEs1LMdpDPTUexbRerdwAVmt 9TH1lPCZM3/K7WVNgAZ8xtOYRUyJSX31VDt6XFovXSiy71fW9dgxfEzJoGyhZu3wRmM3 GYFPR+2h0n+xbGTFYW96ZVGPlVdtjYDefG8gstIx/sepUdimdvQBQcTTLDilIAy1qUf7 PTZOoBxdTreQoFNZtc6c14up7ngcO6LJL68VFNGmoUnREmwz6OXEJ4Ktudk1REMzf3QB JP2QO7fLb0gfsqLzUuRBPxJ3uWKUln9SI/HLQ7wEMKVFshAX5fJxnhspaXcAUJOYvmbg 6fxA== 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 4.15 38/64] usb: ohci: Proper handling of ed_rm_list to handle race condition between usb_kill_urb() and finish_unlinks() Date: Mon, 26 Feb 2018 21:22:15 +0100 Message-Id: <20180226202155.079238024@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180226202153.453363333@linuxfoundation.org> References: <20180226202153.453363333@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?1593496787933214790?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.15-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 diff --git a/drivers/usb/host/ohci-q.c b/drivers/usb/host/ohci-q.c index b2ec8c399363..4ccb85a67bb3 100644 --- a/drivers/usb/host/ohci-q.c +++ b/drivers/usb/host/ohci-q.c @@ -1019,6 +1019,8 @@ static void finish_unlinks(struct ohci_hcd *ohci) * 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 @@ -1077,21 +1079,22 @@ static void finish_unlinks(struct ohci_hcd *ohci) 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)