On Sun, Jun 14, 2020 at 02:02:54PM -0700, Sultan Alsawaf wrote: > From: Sultan Alsawaf <sultan@xxxxxxxxxxxxxxx> > > SMBus block reads can be broken because the read function will just skip > over bytes it doesn't like until reaching a byte that conforms to the > length restrictions for block reads. This is problematic when it isn't > known if the incoming payload is indeed a conforming block read. > > According to the SMBus specification, block reads will only send the > payload length in the first byte, so we can fix this by only considering > the first byte in a sequence for block read length purposes. I'm wondering if this overlaps with [1]. AFAIU that one is also makes sure that the length is not a garbage. [1]: https://lore.kernel.org/linux-i2c/20200613104109.2989-1-mans@xxxxxxxxx/T/#u > Fixes: c3ae106050b9 ("i2c: designware: Implement support for SMBus block read and write") > Signed-off-by: Sultan Alsawaf <sultan@xxxxxxxxxxxxxxx> > --- > drivers/i2c/busses/i2c-designware-master.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c > index d6425ad6e6a3..16d38b8fc19a 100644 > --- a/drivers/i2c/busses/i2c-designware-master.c > +++ b/drivers/i2c/busses/i2c-designware-master.c > @@ -398,7 +398,6 @@ i2c_dw_recv_len(struct dw_i2c_dev *dev, u8 len) > len += (flags & I2C_CLIENT_PEC) ? 2 : 1; > dev->tx_buf_len = len - min_t(u8, len, dev->rx_outstanding); > msgs[dev->msg_read_idx].len = len; > - msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN; > > return len; > } > @@ -430,10 +429,11 @@ i2c_dw_read(struct dw_i2c_dev *dev) > u32 flags = msgs[dev->msg_read_idx].flags; > > regmap_read(dev->map, DW_IC_DATA_CMD, &tmp); > - /* Ensure length byte is a valid value */ > - if (flags & I2C_M_RECV_LEN && > - tmp <= I2C_SMBUS_BLOCK_MAX && tmp > 0) { > - len = i2c_dw_recv_len(dev, tmp); > + if (flags & I2C_M_RECV_LEN) { > + /* Ensure length byte is a valid value */ > + if (tmp <= I2C_SMBUS_BLOCK_MAX && tmp > 0) > + len = i2c_dw_recv_len(dev, tmp); > + msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN; > } > *buf++ = tmp; > dev->rx_outstanding--; > -- > 2.27.0 > -- With Best Regards, Andy Shevchenko
