On Thu, Jun 21, 2018 at 01:31:23PM -0700, Kees Cook wrote: > On Thu, Jun 21, 2018 at 3:00 AM, Heikki Krogerus > <heikki.krogerus@xxxxxxxxxxxxxxx> wrote: > > On Wed, Jun 20, 2018 at 11:28:40AM -0700, Kees Cook wrote: > >> In the quest to remove all stack VLA usage from the kernel[1], this > >> uses the maximum buffer size and adds a sanity check. > >> > >> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx > >> > >> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > >> --- > >> drivers/usb/typec/tps6598x.c | 7 ++++++- > >> 1 file changed, 6 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/usb/typec/tps6598x.c b/drivers/usb/typec/tps6598x.c > >> index 4b4c8d271b27..396193f85e6d 100644 > >> --- a/drivers/usb/typec/tps6598x.c > >> +++ b/drivers/usb/typec/tps6598x.c > >> @@ -81,12 +81,17 @@ struct tps6598x { > >> struct typec_capability typec_cap; > >> }; > >> > >> +#define TPS_MAX_LEN sizeof(u64) > > > > That is not big enough. The registers of this chip can be as big as 64 > > bytes. The identity register alone is 25 bytes, so the above would > > make the driver fail quite fast. Can you set the maximum to 64? > > > > #define TPS_MAX_LEN 64 > > Oops! Yes, thanks, I missed this usage: > > struct tps6598x_rx_identity_reg id; > ... > ret = tps6598x_block_read(tps, TPS_REG_RX_IDENTITY_SOP, > &id, sizeof(id)); > > struct tps6598x_rx_identity_reg { > u8 status; /* 0 1 */ > struct usb_pd_identity identity; /* 1 12 */ > u32 vdo[3]; /* 13 12 */ > > /* size: 25, cachelines: 1, members: 3 */ > /* last cacheline: 25 bytes */ > }; > > But that's still only 25 bytes. Where is the 64? I see these: > > return tps6598x_block_read(tps, reg, val, sizeof(u16)); > return tps6598x_block_read(tps, reg, val, sizeof(u32)); > return tps6598x_block_read(tps, reg, val, sizeof(u64)); > ret = tps6598x_block_read(tps, TPS_REG_RX_IDENTITY_SOP, > &id, sizeof(id)); > ret = tps6598x_block_read(tps, TPS_REG_DATA1, > out_data, out_len); > ret = tps6598x_block_read(tps, TPS_REG_DATA1, &val, sizeof(u8)); > > 1, 2, 4, 8, 25, and "out_len" in tps6598x_exec_cmd(), which is always zero: > > ret = tps6598x_exec_cmd(tps, cmd, 0, NULL, 0, NULL); > ret = tps6598x_exec_cmd(tps, cmd, 0, NULL, 0, NULL); > > I clearly need a v2 of this patch, but I just want to make sure I get > the right value. :) 64 is the max No. Data Bytes at least for the Data1 and Data2 registers, and it seems for few other registers as well [1] (ch. 1.3.2). But I don't mind if you still prefer to use 25 as the value. I'm happy as long as we don't break the driver :-) [1] http://www.ti.com/lit/ug/slvuan1a/slvuan1a.pdf Thanks, -- heikki -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
