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[PATCH 4.4 11/38] staging: iio: ad5933: avoid uninitialized variable in error case

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

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

From: Arnd Bergmann <arnd@arndb.de>

commit 34eee70a7b82b09dbda4cb453e0e21d460dae226 upstream.

The ad5933_i2c_read function returns an error code to indicate
whether it could read data or not. However ad5933_work() ignores
this return code and just accesses the data unconditionally,
which gets detected by gcc as a possible bug:

drivers/staging/iio/impedance-analyzer/ad5933.c: In function 'ad5933_work':
drivers/staging/iio/impedance-analyzer/ad5933.c:649:16: warning: 'status' may be used uninitialized in this function [-Wmaybe-uninitialized]

This adds minimal error handling so we only evaluate the
data if it was correctly read.

Link: https://patchwork.kernel.org/patch/8110281/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/staging/iio/impedance-analyzer/ad5933.c |   17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

--- a/drivers/staging/iio/impedance-analyzer/ad5933.c
+++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
@@ -647,6 +647,7 @@ static void ad5933_work(struct work_stru
 	__be16 buf[2];
 	int val[2];
 	unsigned char status;
+	int ret;
 
 	mutex_lock(&indio_dev->mlock);
 	if (st->state == AD5933_CTRL_INIT_START_FREQ) {
@@ -654,19 +655,22 @@ static void ad5933_work(struct work_stru
 		ad5933_cmd(st, AD5933_CTRL_START_SWEEP);
 		st->state = AD5933_CTRL_START_SWEEP;
 		schedule_delayed_work(&st->work, st->poll_time_jiffies);
-		mutex_unlock(&indio_dev->mlock);
-		return;
+		goto out;
 	}
 
-	ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
+	ret = ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
+	if (ret)
+		goto out;
 
 	if (status & AD5933_STAT_DATA_VALID) {
 		int scan_count = bitmap_weight(indio_dev->active_scan_mask,
 					       indio_dev->masklength);
-		ad5933_i2c_read(st->client,
+		ret = ad5933_i2c_read(st->client,
 				test_bit(1, indio_dev->active_scan_mask) ?
 				AD5933_REG_REAL_DATA : AD5933_REG_IMAG_DATA,
 				scan_count * 2, (u8 *)buf);
+		if (ret)
+			goto out;
 
 		if (scan_count == 2) {
 			val[0] = be16_to_cpu(buf[0]);
@@ -678,8 +682,7 @@ static void ad5933_work(struct work_stru
 	} else {
 		/* no data available - try again later */
 		schedule_delayed_work(&st->work, st->poll_time_jiffies);
-		mutex_unlock(&indio_dev->mlock);
-		return;
+		goto out;
 	}
 
 	if (status & AD5933_STAT_SWEEP_DONE) {
@@ -691,7 +694,7 @@ static void ad5933_work(struct work_stru
 		ad5933_cmd(st, AD5933_CTRL_INC_FREQ);
 		schedule_delayed_work(&st->work, st->poll_time_jiffies);
 	}
-
+out:
 	mutex_unlock(&indio_dev->mlock);
 }
 

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[PATCH 4.4 00/38] 4.4.33-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:40 +0100
  [PATCH 4.4 10/38] pinctrl: cherryview: Prevent possible interrupt storm on resume Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 06/38] coredump: fix unfreezable coredumping task Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 30/38] mei: bus: fix received data size check in NFC fixup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 05/38] swapfile: fix memory corruption via malformed swapfile Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 33/38] i40e: fix call of ndo_dflt_bridge_getlink() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 11/38] staging: iio: ad5933: avoid uninitialized variable in error case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 29/38] iommu/vt-d: Fix dead-locks in disable_dmar_iommu() path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 18/38] toshiba-wmi: Fix loading the driver on non Toshiba laptops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 28/38] iommu/amd: Free domain id when free a domain of struct dma_ops_domain Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 31/38] lib/genalloc.c: start search from start of chunk Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 32/38] hwrng: core - Dont use a stack buffer in add_early_randomness() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 22/38] scsi: qla2xxx: Fix scsi scan hang triggered if adapter fails during init Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 36/38] mmc: mxs: Initialize the spinlock prior to using it Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 38/38] netfilter: fix namespace handling in nf_log_proc_dostring Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
    Re: [PATCH 4.4 38/38] netfilter: fix namespace handling in  nf_log_proc_dostring Pablo Neira Ayuso <pablo@netfilter.org> - 2016-11-17 12:10 +0100
      Re: [PATCH 4.4 38/38] netfilter: fix namespace handling in  nf_log_proc_dostring Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 13:10 +0100
  [PATCH 4.4 35/38] ASoC: sun4i-codec: return error code instead of NULL when create_card fails Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 20/38] iio: hid-sensors: Increase the precision of scale to fix wrong reading interpretation. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 13/38] Revert "staging: nvec: ps2: change serio type to passthrough" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 17/38] drbd: Fix kernel_sendmsg() usage - potential NULL deref Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 37/38] btrfs: qgroup: Prevent qgroup->reserved from going subzero Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 34/38] ACPI / APEI: Fix incorrect return value of ghes_proc() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 12/38] drivers: staging: nvec: remove bogus reset command for PS/2 interface Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 14/38] staging: nvec: remove managed resource from PS2 driver Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 26/38] dmaengine: at_xdmac: fix spurious flag status for mem2mem transfers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 15/38] USB: cdc-acm: fix TIOCMIWAIT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 09/38] pinctrl: cherryview: Serialize register access in suspend/resume Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 01/38] ALSA: info: Return error for invalid read/write Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 12:00 +0100
  [PATCH 4.4 03/38] ASoC: cs4270: fix DAPM stream name mismatch Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 12:00 +0100
  Re: [PATCH 4.4 00/38] 4.4.33-stable review Guenter Roeck <linux@roeck-us.net> - 2016-11-17 23:30 +0100

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