Re: [PATCH v3 11/11] i3c: master: svc: fix possible assignment of the same address to two devices

Miquel Raynal
2024-08-23T16:24:24Z

Hi Frank,

Frank.Li@nxp.com wrote on Mon, 19 Aug 2024 12:02:05 -0400:

> svc_i3c_master_do_daa() {
> ...
> for (i = 0; i < dev_nb; i++) {
> ret = i3c_master_add_i3c_dev_locked(m, addrs[i]);
> if (ret)
> goto rpm_out;
> }
> }
>
> If two devices (A and B) are detected in DAA and address 0xa is assigned to
> device A and 0xb to device B, a failure in i3c_master_add_i3c_dev_locked()
> for device A (addr: 0xa) could prevent device B (addr: 0xb) from being
> registered on the bus. The I3C stack might still consider 0xb a free
> address. If a subsequent Hotjoin occurs, 0xb might be assigned to Device A,
> causing both devices A and B to use the same address 0xb, violating the I3C
> specification.
>
> The return value for i3c_master_add_i3c_dev_locked() should not be checked
> because subsequent steps will scan the entire I3C bus, independent of
> whether i3c_master_add_i3c_dev_locked() returns success.
>
> If device A registration fails, there is still a chance to register device
> B. i3c_master_add_i3c_dev_locked() can reset DAA if a failure occurs while
> retrieving device information.
>
> Cc: stable@kernel.org
> Fixes: 317bacf960a4 ("i3c: master: add enable(disable) hot join in sys entry")
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
> drivers/i3c/master/svc-i3c-master.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> index 2010495906eb3..003565fddc261 100644
> --- a/drivers/i3c/master/svc-i3c-master.c
> +++ b/drivers/i3c/master/svc-i3c-master.c
> @@ -1042,11 +1042,8 @@ static int svc_i3c_master_do_daa(struct i3c_master_controller *m)
> goto rpm_out;
>
> /* Register all devices who participated to the core */
> - for (i = 0; i < dev_nb; i++) {
> - ret = i3c_master_add_i3c_dev_locked(m, addrs[i]);
> - if (ret)
> - goto rpm_out;
> - }
> + for (i = 0; i < dev_nb; i++)
> + i3c_master_add_i3c_dev_locked(m, addrs[i]);

Makes sense, but please explain why don't check the return value in a
comment (your commit log is good).

>
> /* Configure IBI auto-rules */
> ret = svc_i3c_update_ibirules(master);
>

With the comment added,

Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>

Thanks,
Miquèl