[PATCH v5 08/17] i3c: renesas: Fix out-of-bounds access for newdevs mask

[Claudiu Beznea]

From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>

When software initiates DAA (Dynamic Address Assignment), the controller
reports the result via the NRSPQP (Normal Response Queue Port Register).
The data length field of the response descriptor, which is accessible
through the NRSPQP register, indicates the number of devices remaining
after DAA. Consequently, when the bus is empty, this field contains the
maximum number of devices supported by the controller (8 for the Renesas
I3C controller).

Adjust the condition that computes the newly discovered devices bitmask
to prevent an out-of-bounds when the I3C bus is empty.

Fixes: e7218986319b ("i3c: renesas: Add suspend/resume support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
---

Changes in v5:
- none; this patch is new

 drivers/i3c/master/renesas-i3c.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/i3c/master/renesas-i3c.c b/drivers/i3c/master/renesas-i3c.c
index b9784d238f61..c459e40fd5ff 100644
--- a/drivers/i3c/master/renesas-i3c.c
+++ b/drivers/i3c/master/renesas-i3c.c
@@ -703,7 +703,11 @@ static int renesas_i3c_daa(struct i3c_master_controller *m)
 
 	renesas_i3c_wait_xfer(i3c, xfer);
 
-	newdevs = GENMASK(i3c->maxdevs - cmd->rx_count - 1, 0);
+	if (cmd->rx_count >= i3c->maxdevs)
+		newdevs = 0;
+	else
+		newdevs = GENMASK(i3c->maxdevs - cmd->rx_count - 1, 0);
+
 	newdevs &= ~olddevs;
 
 	for (pos = 0; pos < i3c->maxdevs; pos++) {
-- 
2.43.0