[PATCH 6.18 395/752] ntb: ntb_hw_switchtec: Fix shift-out-of-bounds for 0 mw lut

Sasha Levin
2026-02-28T17:53:38Z

From: Maciej Grochowski <Maciej.Grochowski@sony.com>

[ Upstream commit 186615f8855a0be4ee7d3fcd09a8ecc10e783b08 ]

Number of MW LUTs depends on NTB configuration and can be set to zero,
in such scenario rounddown_pow_of_two will cause undefined behaviour and
should not be performed.
This patch ensures that rounddown_pow_of_two is called on valid value.

Signed-off-by: Maciej Grochowski <Maciej.Grochowski@sony.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/ntb/hw/mscc/ntb_hw_switchtec.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/ntb/hw/mscc/ntb_hw_switchtec.c b/drivers/ntb/hw/mscc/ntb_hw_switchtec.c
index f15ebab138144..0536521fa6ccc 100644
--- a/drivers/ntb/hw/mscc/ntb_hw_switchtec.c
+++ b/drivers/ntb/hw/mscc/ntb_hw_switchtec.c
@@ -1202,7 +1202,8 @@ static void switchtec_ntb_init_mw(struct switchtec_ntb *sndev)
sndev->mmio_self_ctrl);

sndev->nr_lut_mw = ioread16(&sndev->mmio_self_ctrl->lut_table_entries);
- sndev->nr_lut_mw = rounddown_pow_of_two(sndev->nr_lut_mw);
+ if (sndev->nr_lut_mw)
+ sndev->nr_lut_mw = rounddown_pow_of_two(sndev->nr_lut_mw);

dev_dbg(&sndev->stdev->dev, "MWs: %d direct, %d lut\n",
sndev->nr_direct_mw, sndev->nr_lut_mw);
@@ -1212,7 +1213,8 @@ static void switchtec_ntb_init_mw(struct switchtec_ntb *sndev)

sndev->peer_nr_lut_mw =
ioread16(&sndev->mmio_peer_ctrl->lut_table_entries);
- sndev->peer_nr_lut_mw = rounddown_pow_of_two(sndev->peer_nr_lut_mw);
+ if (sndev->peer_nr_lut_mw)
+ sndev->peer_nr_lut_mw = rounddown_pow_of_two(sndev->peer_nr_lut_mw);

dev_dbg(&sndev->stdev->dev, "Peer MWs: %d direct, %d lut\n",
sndev->peer_nr_direct_mw, sndev->peer_nr_lut_mw);
--
2.51.0