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[PATCH 4.9 005/125] thermal: max77620: fix device-node reference imbalance

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

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

From: Johan Hovold <johan@kernel.org>

commit c592fafbdbb6b1279b76a54722d1465ca77e5bde upstream.

The thermal child device reuses the parent MFD-device device-tree node
when registering a thermal zone, but did not take a reference to the
node.

This leads to a reference imbalance, and potential use-after-free, when
the node reference is dropped by the platform-bus device destructor
(once for the child and later again for the parent).

Fix this by dropping any reference already held to a device-tree node
and getting a reference to the parent's node which will be balanced on
reprobe or on platform-device release, whichever comes first.

Note that simply clearing the of_node pointer on probe errors and on
driver unbind would not allow the use of device-managed resources as
specifically thermal_zone_of_sensor_unregister() claims that a valid
device-tree node pointer is needed during deregistration (even if it
currently does not seem to use it).

Fixes: ec4664b3fd6d ("thermal: max77620: Add thermal driver for reporting junction temp")
Cc: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/thermal/max77620_thermal.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/thermal/max77620_thermal.c
+++ b/drivers/thermal/max77620_thermal.c
@@ -104,8 +104,6 @@ static int max77620_thermal_probe(struct
 		return -EINVAL;
 	}
 
-	pdev->dev.of_node = pdev->dev.parent->of_node;
-
 	mtherm->dev = &pdev->dev;
 	mtherm->rmap = dev_get_regmap(pdev->dev.parent, NULL);
 	if (!mtherm->rmap) {
@@ -113,6 +111,14 @@ static int max77620_thermal_probe(struct
 		return -ENODEV;
 	}
 
+	/*
+	 * Drop any current reference to a device-tree node and get a
+	 * reference to the parent's node which will be balanced on reprobe or
+	 * on platform-device release.
+	 */
+	of_node_put(pdev->dev.of_node);
+	pdev->dev.of_node = of_node_get(pdev->dev.parent->of_node);
+
 	mtherm->tz_device = devm_thermal_zone_of_sensor_register(&pdev->dev, 0,
 				mtherm, &max77620_thermal_ops);
 	if (IS_ERR(mtherm->tz_device)) {

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[PATCH 4.9 000/125] 4.9.40-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 068/125] ipmi: use rcu lock around call to intf->handlers->sender() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 046/125] PCI: rockchip: Use normal register bank for config accessors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 042/125] powerpc/asm: Mark cr0 as clobbered in mftb() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 035/125] scsi: Add STARGET_CREATED_REMOVE state to scsi_target_state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 044/125] af_key: Fix sadb_x_ipsecrequest parsing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 037/125] xen/scsiback: Fix a TMR related use-after-free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 053/125] usb: storage: return on error to avoid a null pointer dereference Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 030/125] ASoC: compress: Derive substream from stream based on direction Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 008/125] ath9k: fix tx99 bus error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 027/125] wlcore: fix 64K page support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 056/125] usb: renesas_usbhs: gadget: disable all eps when the driver stops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 047/125] PCI/PM: Restore the status of PCI devices across hibernation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 049/125] xhci: fix 20000ms port resume timeout Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 028/125] btrfs: Dont clear SGID when inheriting ACLs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 033/125] PM / Domains: Fix unsafe iteration over modified list of domains Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 052/125] [media] mxl111sf: Fix driver to use heap allocate buffers for USB messages Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 009/125] ath9k: fix an invalid pointer dereference in ath9k_rng_stop() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 041/125] powerpc: Fix emulation of mfocrf in emulate_step() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 043/125] powerpc/mm/radix: Properly clear process table entry Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 039/125] powerpc/64: Fix atomic64_inc_not_zero() to return an int Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 034/125] scsi: ses: do not add a device to an enclosure if enclosure_add_links() fails. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 029/125] igb: Explicitly select page 0 at initialization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 032/125] PM / Domains: Fix unsafe iteration over modified list of domain providers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 036/125] iscsi-target: Add login_keys_workaround attribute for non RFC initiators Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 054/125] USB: cdc-acm: add device-id for quirky printer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 071/125] f2fs: sanity check size of nat and sit cache Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 050/125] xhci: Fix NULL pointer dereference when cleaning up streams for removed host Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 069/125] ipmi:ssif: Add missing unlock in error branch Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 026/125] Bluetooth: use constant time memory comparison for secret values Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 031/125] PM / Domains: Fix unsafe iteration over modified list of device links Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 040/125] powerpc: Fix emulation of mcrf in emulate_step() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 023/125] perf intel-pt: Ensure never to set last_ip when packet count is zero Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 003/125] dm mpath: cleanup -Wbool-operation warning in choose_pgpath() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 017/125] NFC: Add sockaddr length checks before accessing sa_family in bind handlers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 018/125] perf intel-pt: Move decoder error setting into one condition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 005/125] thermal: max77620: fix device-node reference imbalance Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 006/125] thermal: cpu_cooling: Avoid accessing potentially freed structures Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 004/125] [media] s5p-jpeg: dont return a random width/height Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 001/125] disable new gcc-7.1.1 warnings for now Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 015/125] nfc: Ensure presence of required attributes in the activate_target handler Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 020/125] perf intel-pt: Fix missing stack clear Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 002/125] [media] ir-core: fix gcc-7 warning on bool arithmetic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 012/125] NFC: nfcmrvl: do not use device-managed resources Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 007/125] ath9k: fix tx99 use after free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 021/125] perf intel-pt: Ensure IP is zero when state is INTEL_PT_STATE_NO_IP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 011/125] NFC: nfcmrvl_uart: add missing tty-device sanity check Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 014/125] NFC: nfcmrvl: fix firmware-management initialisation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 016/125] nfc: Fix the sockaddr length sanitization in llcp_sock_connect Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 019/125] perf intel-pt: Improve sample timestamp Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 010/125] NFC: fix broken device allocation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 013/125] NFC: nfcmrvl: use nfc-device for firmware download Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  Re: [PATCH 4.9 000/125] 4.9.40-stable review Guenter Roeck <linux@roeck-us.net> - 2017-07-26 05:00 +0200
  Re: [PATCH 4.9 000/125] 4.9.40-stable review Sumit Semwal <sumit.semwal@linaro.org> - 2017-07-26 16:20 +0200
    Re: [PATCH 4.9 000/125] 4.9.40-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-26 22:00 +0200
  Re: [PATCH 4.9 000/125] 4.9.40-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-07-26 16:30 +0200

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