[PATCH 6.1 325/451] media: dvb-frontends: avoid stack overflow warnings with clang

Sasha Levin
2024-03-24T23:17:23Z

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit 7a4cf27d1f0538f779bf31b8c99eda394e277119 ]

A previous patch worked around a KASAN issue in stv0367, now a similar
problem showed up with clang:

drivers/media/dvb-frontends/stv0367.c:1222:12: error: stack frame size (3624) exceeds limit (2048) in 'stv0367ter_set_frontend' [-Werror,-Wframe-larger-than]
1214 | static int stv0367ter_set_frontend(struct dvb_frontend *fe)

Rework the stv0367_writereg() function to be simpler and mark both
register access functions as noinline_for_stack so the temporary
i2c_msg structures do not get duplicated on the stack when KASAN_STACK
is enabled.

Fixes: 3cd890dbe2a4 ("media: dvb-frontends: fix i2c access helpers for KASAN")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/media/dvb-frontends/stv0367.c | 34 +++++++--------------------
1 file changed, 8 insertions(+), 26 deletions(-)

diff --git a/drivers/media/dvb-frontends/stv0367.c b/drivers/media/dvb-frontends/stv0367.c
index 04556b77c16c9..0977564a4a1a4 100644
--- a/drivers/media/dvb-frontends/stv0367.c
+++ b/drivers/media/dvb-frontends/stv0367.c
@@ -118,50 +118,32 @@ static const s32 stv0367cab_RF_LookUp2[RF_LOOKUP_TABLE2_SIZE][RF_LOOKUP_TABLE2_S
}
};

-static
-int stv0367_writeregs(struct stv0367_state *state, u16 reg, u8 *data, int len)
+static noinline_for_stack
+int stv0367_writereg(struct stv0367_state *state, u16 reg, u8 data)
{
- u8 buf[MAX_XFER_SIZE];
+ u8 buf[3] = { MSB(reg), LSB(reg), data };
struct i2c_msg msg = {
.addr = state->config->demod_address,
.flags = 0,
.buf = buf,
- .len = len + 2
+ .len = 3,
};
int ret;

- if (2 + len > sizeof(buf)) {
- printk(KERN_WARNING
- "%s: i2c wr reg=%04x: len=%d is too big!\n",
- KBUILD_MODNAME, reg, len);
- return -EINVAL;
- }
-
-
- buf[0] = MSB(reg);
- buf[1] = LSB(reg);
- memcpy(buf + 2, data, len);
-
if (i2cdebug)
printk(KERN_DEBUG "%s: [%02x] %02x: %02x\n", __func__,
- state->config->demod_address, reg, buf[2]);
+ state->config->demod_address, reg, data);

ret = i2c_transfer(state->i2c, &msg, 1);
if (ret != 1)
printk(KERN_ERR "%s: i2c write error! ([%02x] %02x: %02x)\n",
- __func__, state->config->demod_address, reg, buf[2]);
+ __func__, state->config->demod_address, reg, data);

return (ret != 1) ? -EREMOTEIO : 0;
}

-static int stv0367_writereg(struct stv0367_state *state, u16 reg, u8 data)
-{
- u8 tmp = data; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
-
- return stv0367_writeregs(state, reg, &tmp, 1);
-}
-
-static u8 stv0367_readreg(struct stv0367_state *state, u16 reg)
+static noinline_for_stack
+u8 stv0367_readreg(struct stv0367_state *state, u16 reg)
{
u8 b0[] = { 0, 0 };
u8 b1[] = { 0 };
--
2.43.0