[PATCH 4.14 162/167] media: r820t: fix r820t_write_reg for KASAN

Greg Kroah-Hartman
2018-02-21T12:49:33Z

From: Arnd Bergmann <arnd@arndb.de>

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.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/media/tuners/r820t.c
+++ b/drivers/media/tuners/r820t.c
@@ -396,9 +396,11 @@ 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)
@@ -411,17 +413,18 @@ 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)