From: Jonas Jelonek Date: Sun, 31 Aug 2025 10:04:47 +0000 (+0000) Subject: i2c: rtl9300: ensure data length is within supported range X-Git-Tag: v6.17-rc5~1^2^2~1 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=06418cb5a1a542a003fdb4ad8e76ea542d57cfba;p=users%2Fgriffoul%2Flinux.git i2c: rtl9300: ensure data length is within supported range Add an explicit check for the xfer length to 'rtl9300_i2c_config_xfer' to ensure the data length isn't within the supported range. In particular a data length of 0 is not supported by the hardware and causes unintended or destructive behaviour. This limitation becomes obvious when looking at the register documentation [1]. 4 bits are reserved for DATA_WIDTH and the value of these 4 bits is used as N + 1, allowing a data length range of 1 <= len <= 16. Affected by this is the SMBus Quick Operation which works with a data length of 0. Passing 0 as the length causes an underflow of the value due to: (len - 1) & 0xf and effectively specifying a transfer length of 16 via the registers. This causes a 16-byte write operation instead of a Quick Write. For example, on SFP modules without write-protected EEPROM this soft-bricks them by overwriting some initial bytes. For completeness, also add a quirk for the zero length. [1] https://svanheule.net/realtek/longan/register/i2c_mst1_ctrl2 Fixes: c366be720235 ("i2c: Add driver for the RTL9300 I2C controller") Cc: stable@vger.kernel.org # v6.13+ Signed-off-by: Jonas Jelonek Tested-by: Sven Eckelmann Reviewed-by: Chris Packham Tested-by: Chris Packham # On RTL9302C based board Tested-by: Markus Stockhausen Signed-off-by: Andi Shyti Link: https://lore.kernel.org/r/20250831100457.3114-3-jelonek.jonas@gmail.com --- diff --git a/drivers/i2c/busses/i2c-rtl9300.c b/drivers/i2c/busses/i2c-rtl9300.c index 1a63790f1957..2b3e80aa1bdf 100644 --- a/drivers/i2c/busses/i2c-rtl9300.c +++ b/drivers/i2c/busses/i2c-rtl9300.c @@ -99,6 +99,9 @@ static int rtl9300_i2c_config_xfer(struct rtl9300_i2c *i2c, struct rtl9300_i2c_c { u32 val, mask; + if (len < 1 || len > 16) + return -EINVAL; + val = chan->bus_freq << RTL9300_I2C_MST_CTRL2_SCL_FREQ_OFS; mask = RTL9300_I2C_MST_CTRL2_SCL_FREQ_MASK; @@ -323,7 +326,7 @@ static const struct i2c_algorithm rtl9300_i2c_algo = { }; static struct i2c_adapter_quirks rtl9300_i2c_quirks = { - .flags = I2C_AQ_NO_CLK_STRETCH, + .flags = I2C_AQ_NO_CLK_STRETCH | I2C_AQ_NO_ZERO_LEN, .max_read_len = 16, .max_write_len = 16, };