From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x225x7ydbiGX+zBJ4LGYHCe4yJJ7M4rcqsSnrNTKBili9ievSFeOzU3hprt86MWhzm4TXMXyq ARC-Seal: i=1; a=rsa-sha256; t=1519676485; cv=none; d=google.com; s=arc-20160816; b=mCAZVN9T17739UvD+td6coQ9Sdz3UxB29rFCGmWnb2NkoDpJRNFCG22xVSe7o9rmHO 0HPtSeXCGkoSQunAOjI3tfJwL3ZyDC7BcxlwtIV6Zhg9kHFa9td20RiQ4iV76ooxoOF1 F2qvTB+t1PBPqHwuhwz0tZEcDIJY4iW58luDv+89YMCqVS8FCyyia3OAfZ7Vaf9u1ooy ywiXTSL+qQreH2Sd1KHJ03swRA1LFoXY2foufxZa180121VYCL0PSF48flwFoV4ucuA/ lprKmydv7Bp45G5GbC32JASVhuxug3aMaIx9h9q42J2LwRQ16PcV5aF3KpnqD9XzKGlA Ezag== 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=if9oOJ6fXovO1Tm8YiXbFAI0SQs3x9VXGdCe6S5r86Q=; b=BDNK37Bgf6GzrYJzBMOtIGV44J0GR7q5nS/EdTpesqPHbDK/smqGpnz1+XwXwyZWJV iTolfub0/xE9/xrSZhysp0wYpXnn3Vbcy2kg8tAGsYU8DyT3J0FoBzoAf1f33qXRRll3 lYyajjT4ncWVm1y8a1rOw8cfsTmdPNIrsjBZG6uNjBmcXwcjHaklfIBd2iMeY8IAanqa KlCVU/i/t26l3Z5bgdqOwiP6jYW1ZPmGfx/3aYTJNMXfFX0Kcet4OuHwuwIyE2vttsXC +HCXzmR/71pDkLE1PSAprQxuPUSy6vnjIztE2IiRb6ONPjgQoXsyPB4I53iIDLi3GxNM XR9w== 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 4.9 14/39] usb: ohci: Proper handling of ed_rm_list to handle race condition between usb_kill_urb() and finish_unlinks() Date: Mon, 26 Feb 2018 21:20:35 +0100 Message-Id: <20180226201644.311208882@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180226201643.660109883@linuxfoundation.org> References: <20180226201643.660109883@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?1593496290916100925?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-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)