linux-kernel - [PATCH v2] vfio/mlx5: fix possible overflow in tracking max message size

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Message-ID: <20250701144017.2410-2-a.sadovnikov@ispras.ru>
Date: Tue,  1 Jul 2025 14:40:17 +0000
From: Artem Sadovnikov <a.sadovnikov@...ras.ru>
To: kvm@...r.kernel.org
Cc: Artem Sadovnikov <a.sadovnikov@...ras.ru>,
	Yishai Hadas <yishaih@...dia.com>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
	Kevin Tian <kevin.tian@...el.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	linux-kernel@...r.kernel.org,
	lvc-project@...uxtesting.org
Subject: [PATCH v2] vfio/mlx5: fix possible overflow in tracking max message size

MLX cap pg_track_log_max_msg_size consists of 5 bits, value of which is
used as power of 2 for max_msg_size. This can lead to multiplication
overflow between max_msg_size (u32) and integer constant, and afterwards
incorrect value is being written to rq_size.

Fix this issue by extending integer constant to u64 type.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Suggested-by: Alex Williamson <alex.williamson@...hat.com>
Signed-off-by: Artem Sadovnikov <a.sadovnikov@...ras.ru>
---
Changes from v1:
- The constant type was changed instead of variable type.
- The patch name was accidentally cut and is now fixed.
- LKML: https://lore.kernel.org/all/20250629095843.13349-1-a.sadovnikov@ispras.ru/
---
 drivers/vfio/pci/mlx5/cmd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/mlx5/cmd.c b/drivers/vfio/pci/mlx5/cmd.c
index 5b919a0b2524..a92b095b90f6 100644
--- a/drivers/vfio/pci/mlx5/cmd.c
+++ b/drivers/vfio/pci/mlx5/cmd.c
@@ -1523,8 +1523,8 @@ int mlx5vf_start_page_tracker(struct vfio_device *vdev,
 	log_max_msg_size = MLX5_CAP_ADV_VIRTUALIZATION(mdev, pg_track_log_max_msg_size);
 	max_msg_size = (1ULL << log_max_msg_size);
 	/* The RQ must hold at least 4 WQEs/messages for successful QP creation */
-	if (rq_size < 4 * max_msg_size)
-		rq_size = 4 * max_msg_size;
+	if (rq_size < 4ULL * max_msg_size)
+		rq_size = 4ULL * max_msg_size;
 
 	memset(tracker, 0, sizeof(*tracker));
 	tracker->uar = mlx5_get_uars_page(mdev);
-- 
2.43.0