Patch "media: r820t: fix r820t_write_reg for KASAN" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

media: r820t: fix r820t_write_reg for KASAN

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     media-r820t-fix-r820t_write_reg-for-kasan.patch

and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Arnd Bergmann <[email protected]>
Date: Thu, 30 Nov 2017 06:08:05 -0500
Subject: media: r820t: fix r820t_write_reg for KASAN

From: Arnd Bergmann <[email protected]>

commit 16c3ada89cff9a8c2a0eea34ffa1aa20af3f6008 upstream.

With CONFIG_KASAN, we get an overly long stack frame due to inlining the register access functions:

drivers/media/tuners/r820t.c: In function 'generic_set_freq.isra.7':
drivers/media/tuners/r820t.c:1334:1: error: the frame size of 2880 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]

This is caused by a gcc bug that has now been fixed in gcc-8. To work around the problem, we can pass the register data through a local variable that older gcc versions can optimize out as well.

---
 drivers/media/tuners/r820t.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

@@ -410,9 +410,11 @@ static int r820t_write(struct r820t_priv
 	return 0;
 }
 
-static int r820t_write_reg(struct r820t_priv *priv, u8 reg, u8 val)
+static inline int r820t_write_reg(struct r820t_priv *priv, u8 reg, u8 val)
 {
-	return r820t_write(priv, reg, &val, 1);
+	u8 tmp = val; /* work around GCC PR81715 with asan-stack=1 */
+
+	return r820t_write(priv, reg, &tmp, 1);
 }
 
 static int r820t_read_cache_reg(struct r820t_priv *priv, int reg)

@@ -425,17 +427,18 @@ static int r820t_read_cache_reg(struct r
 		return -EINVAL;
 }
 
-static int r820t_write_reg_mask(struct r820t_priv *priv, u8 reg, u8 val,
+static inline int r820t_write_reg_mask(struct r820t_priv *priv, u8 reg, u8 val,
 				u8 bit_mask)
 {
+	u8 tmp = val;
 	int rc = r820t_read_cache_reg(priv, reg);
 
 	if (rc < 0)
 		return rc;
 
-	val = (rc & ~bit_mask) | (val & bit_mask);
+	tmp = (rc & ~bit_mask) | (tmp & bit_mask);
 
-	return r820t_write(priv, reg, &val, 1);
+	return r820t_write(priv, reg, &tmp, 1);
 }
 
 static int r820t_read(struct r820t_priv *priv, u8 reg, u8 *val, int len)

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/arm-spear600-add-missing-interrupt-parent-of-rtc.patch queue-4.4/media-r820t-fix-r820t_write_reg-for-kasan.patch queue-4.4/arm-dts-sti-add-gpio-polarity-for-hdmi-hpd-gpio-property.patch queue-4.4/arm-spear13xx-fix-spics-gpio-controller-s-warning.patch queue-4.4/x86-fix-build-warnign-with-32-bit-pae.patch queue-4.4/mm-hide-a-warning-for-compile_test.patch queue-4.4/arm-pxa-tosa-bt-add-module_license-tag.patch queue-4.4/arm-dts-s5pv210-add-interrupt-parent-for-ohci.patch queue-4.4/arm-spear13xx-fix-dmas-cells.patch