From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:38652 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751464AbdH1JU7 (ORCPT ); Mon, 28 Aug 2017 05:20:59 -0400 Subject: patch "USB: core: Avoid race of async_completed() w/ usbdev_release()" added to usb-testing To: dianders@chromium.org, gregkh@linuxfoundation.org, stable@vger.kernel.org, stern@rowland.harvard.edu From: Date: Mon, 28 Aug 2017 11:20:54 +0200 Message-ID: <15039120542416@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled USB: core: Avoid race of async_completed() w/ usbdev_release() to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-testing branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will be merged to the usb-next branch sometime soon, after it passes testing, and the merge window is open. If you have any questions about this process, please let me know. >>From ed62ca2f4f51c17841ea39d98c0c409cb53a3e10 Mon Sep 17 00:00:00 2001 From: Douglas Anderson Date: Thu, 10 Aug 2017 15:42:22 -0700 Subject: USB: core: Avoid race of async_completed() w/ usbdev_release() While running reboot tests w/ a specific set of USB devices (and slub_debug enabled), I found that once every few hours my device would be crashed with a stack that looked like this: [ 14.012445] BUG: spinlock bad magic on CPU#0, modprobe/2091 [ 14.012460] lock: 0xffffffc0cb055978, .magic: ffffffc0, .owner: cryption contexts: %lu/%lu [ 14.012460] /1025536097, .owner_cpu: 0 [ 14.012466] CPU: 0 PID: 2091 Comm: modprobe Not tainted 4.4.79 #352 [ 14.012468] Hardware name: Google Kevin (DT) [ 14.012471] Call trace: [ 14.012483] [<....>] dump_backtrace+0x0/0x160 [ 14.012487] [<....>] show_stack+0x20/0x28 [ 14.012494] [<....>] dump_stack+0xb4/0xf0 [ 14.012500] [<....>] spin_dump+0x8c/0x98 [ 14.012504] [<....>] spin_bug+0x30/0x3c [ 14.012508] [<....>] do_raw_spin_lock+0x40/0x164 [ 14.012515] [<....>] _raw_spin_lock_irqsave+0x64/0x74 [ 14.012521] [<....>] __wake_up+0x2c/0x60 [ 14.012528] [<....>] async_completed+0x2d0/0x300 [ 14.012534] [<....>] __usb_hcd_giveback_urb+0xc4/0x138 [ 14.012538] [<....>] usb_hcd_giveback_urb+0x54/0xf0 [ 14.012544] [<....>] xhci_irq+0x1314/0x1348 [ 14.012548] [<....>] usb_hcd_irq+0x40/0x50 [ 14.012553] [<....>] handle_irq_event_percpu+0x1b4/0x3f0 [ 14.012556] [<....>] handle_irq_event+0x4c/0x7c [ 14.012561] [<....>] handle_fasteoi_irq+0x158/0x1c8 [ 14.012564] [<....>] generic_handle_irq+0x30/0x44 [ 14.012568] [<....>] __handle_domain_irq+0x90/0xbc [ 14.012572] [<....>] gic_handle_irq+0xcc/0x18c Investigation using kgdb() found that the wait queue that was passed into wake_up() had been freed (it was filled with slub_debug poison). I analyzed and instrumented the code and reproduced. My current belief is that this is happening: 1. async_completed() is called (from IRQ). Moves "as" onto the completed list. 2. On another CPU, proc_reapurbnonblock_compat() calls async_getcompleted(). Blocks on spinlock. 3. async_completed() releases the lock; keeps running; gets blocked midway through wake_up(). 4. proc_reapurbnonblock_compat() => async_getcompleted() gets the lock; removes "as" from completed list and frees it. 5. usbdev_release() is called. Frees "ps". 6. async_completed() finally continues running wake_up(). ...but wake_up() has a pointer to the freed "ps". The instrumentation that led me to believe this was based on adding some trace_printk() calls in a select few functions and then using kdb's "ftdump" at crash time. The trace follows (NOTE: in the trace below I cheated a little bit and added a udelay(1000) in async_completed() after releasing the spinlock because I wanted it to trigger quicker): <...>-2104 0d.h2 13759034us!: async_completed at start: as=ffffffc0cc638200 mtpd-2055 3.... 13759356us : async_getcompleted before spin_lock_irqsave mtpd-2055 3d..1 13759362us : async_getcompleted after list_del_init: as=ffffffc0cc638200 mtpd-2055 3.... 13759371us+: proc_reapurbnonblock_compat: free_async(ffffffc0cc638200) mtpd-2055 3.... 13759422us+: async_getcompleted before spin_lock_irqsave mtpd-2055 3.... 13759479us : usbdev_release at start: ps=ffffffc0cc042080 mtpd-2055 3.... 13759487us : async_getcompleted before spin_lock_irqsave mtpd-2055 3.... 13759497us!: usbdev_release after kfree(ps): ps=ffffffc0cc042080 <...>-2104 0d.h2 13760294us : async_completed before wake_up(): as=ffffffc0cc638200 To fix this problem we can just move the wake_up() under the ps->lock. There should be no issues there that I'm aware of. Signed-off-by: Douglas Anderson Acked-by: Alan Stern Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/devio.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c index ebe27595c4af..0ff0feddfd1f 100644 --- a/drivers/usb/core/devio.c +++ b/drivers/usb/core/devio.c @@ -623,6 +623,8 @@ static void async_completed(struct urb *urb) if (as->status < 0 && as->bulk_addr && as->status != -ECONNRESET && as->status != -ENOENT) cancel_bulk_urbs(ps, as->bulk_addr); + + wake_up(&ps->wait); spin_unlock(&ps->lock); if (signr) { @@ -630,8 +632,6 @@ static void async_completed(struct urb *urb) put_pid(pid); put_cred(cred); } - - wake_up(&ps->wait); } static void destroy_async(struct usb_dev_state *ps, struct list_head *list) -- 2.14.1