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[PATCH 3.10 05/64] HID: usbhid: fix recursive deadlock

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3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ioan-Adrian Ratiu <adi@adirat.com>

commit e470127e9606b1fa151c4184243e61296d1e0c0f upstream.

The critical section protected by usbhid->lock in hid_ctrl() is too
big and because of this it causes a recursive deadlock. "Too big" means
the case statement and the call to hid_input_report() do not need to be
protected by the spinlock (no URB operations are done inside them).

The deadlock happens because in certain rare cases drivers try to grab
the lock while handling the ctrl irq which grabs the lock before them
as described above. For example newer wacom tablets like 056a:033c try
to reschedule proximity reads from wacom_intuos_schedule_prox_event()
calling hid_hw_request() -> usbhid_request() -> usbhid_submit_report()
which tries to grab the usbhid lock already held by hid_ctrl().

There are two ways to get out of this deadlock:
    1. Make the drivers work "around" the ctrl critical region, in the
    wacom case for ex. by delaying the scheduling of the proximity read
    request itself to a workqueue.
    2. Shrink the critical region so the usbhid lock protects only the
    instructions which modify usbhid state, calling hid_input_report()
    with the spinlock unlocked, allowing the device driver to grab the
    lock first, finish and then grab the lock afterwards in hid_ctrl().

This patch implements the 2nd solution.

Signed-off-by: Ioan-Adrian Ratiu <adi@adirat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/hid/usbhid/hid-core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -490,8 +490,6 @@ static void hid_ctrl(struct urb *urb)
 	struct usbhid_device *usbhid = hid->driver_data;
 	int unplug = 0, status = urb->status;
 
-	spin_lock(&usbhid->lock);
-
 	switch (status) {
 	case 0:			/* success */
 		if (usbhid->ctrl[usbhid->ctrltail].dir == USB_DIR_IN)
@@ -511,6 +509,8 @@ static void hid_ctrl(struct urb *urb)
 		hid_warn(urb->dev, "ctrl urb status %d received\n", status);
 	}
 
+	spin_lock(&usbhid->lock);
+
 	if (unplug) {
 		usbhid->ctrltail = usbhid->ctrlhead;
 	} else {

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[PATCH 3.10 00/64] 3.10.97-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 03/64] crypto: algif_hash - Only export and import on sockets with data Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 31/64] ALSA: rawmidi: Remove kernel WARNING for NULL user-space buffer check Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 55/64] crypto: af_alg - Disallow bind/setkey/... after accept(2) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 25/64] fix sysvfs symlinks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 01/64] recordmcount: Fix endianness handling bug for nop_mcount Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 37/64] ALSA: seq: Fix lockdep warnings due to double mutex locks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 60/64] crypto: algif_hash - wait for crypto_ahash_init() to complete Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 59/64] ahci: Intel DNV device IDs SATA Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 07/64] kernel/signal.c: unexport sigsuspend() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 24/64] [media] media: vb2 dma-contig: Fully cache synchronise buffers in prepare and finish Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 39/64] ALSA: timer: Fix leftover link at closing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 28/64] ALSA: compress: Disable GET_CODEC_CAPS ioctl for some architectures Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 23/64] [media] v4l2-compat-ioctl32: fix alignment for ARM64 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 05/64] HID: usbhid: fix recursive deadlock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 57/64] AHCI: Fix softreset failed issue of Port Multiplier Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 04/64] dm btree: fix leak of bufio-backed block in btree_split_sibling error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:40 +0100
  [PATCH 3.10 16/64] vTPM: fix memory allocation flag for rtce buffer at kernel boot Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 14/64] wlcore/wl12xx: spi: fix oops on firmware load Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 15/64] wlcore/wl12xx: spi: fix NULL pointer dereference (Oops) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 22/64] parisc: Fix __ARCH_SI_PREAMBLE_SIZE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 19/64] [PATCH] fix calculation of meta_bg descriptor backups Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 18/64] jbd2: Fix unreclaimed pages after truncate in data=journal mode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 17/64] mtd: mtdpart: fix add_mtd_partitions error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 12/64] spi: atmel: Fix DMA-setup for transfers with more than 8 bits per word Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 21/64] parisc: Fix syscall restarts Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 11/64] Revert "dm mpath: fix stalls when handling invalid ioctls" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 13/64] spi: fix parent-device reference leak Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  [PATCH 3.10 02/64] xhci: fix placement of call to usb_disabled() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 00:50 +0100
  Re: [PATCH 3.10 00/64] 3.10.97-stable review Guenter Roeck <linux@roeck-us.net> - 2016-02-15 06:30 +0100
    Re: [PATCH 3.10 00/64] 3.10.97-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-15 19:20 +0100
  Re: [PATCH 3.10 00/64] 3.10.97-stable review Guenter Roeck <linux@roeck-us.net> - 2016-02-15 16:50 +0100
  Re: [PATCH 3.10 00/64] 3.10.97-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-02-15 18:20 +0100
    Re: [PATCH 3.10 00/64] 3.10.97-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-02-17 21:40 +0100
      Re: [PATCH 3.10 00/64] 3.10.97-stable review Willy Tarreau <w@1wt.eu> - 2016-02-18 00:30 +0100
        Re: [PATCH 3.10 00/64] 3.10.97-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-02-18 00:40 +0100
          Re: [PATCH 3.10 00/64] 3.10.97-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-02-18 04:30 +0100
            Re: [PATCH 3.10 00/64] 3.10.97-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-19 23:30 +0100
    Re: [PATCH 3.10 00/64] 3.10.97-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-17 21:40 +0100

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