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Subject[PATCH sparc-next] sunvdc: Remove VLA usage
In the quest to remove all stack VLA usage from the kernel[1], this moves
the math for cookies calculation into macros and allocates a fixed size
array for the maximum number of cookies and adds a runtime sanity check.
(Note that the size was always fixed, but just hidden from the compiler.)

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/block/sunvdc.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/block/sunvdc.c b/drivers/block/sunvdc.c
index 5ca56bfae63c..f68e9baffad7 100644
--- a/drivers/block/sunvdc.c
+++ b/drivers/block/sunvdc.c
@@ -36,6 +36,10 @@ MODULE_VERSION(DRV_MODULE_VERSION);
#define VDC_TX_RING_SIZE 512
#define VDC_DEFAULT_BLK_SIZE 512

+#define MAX_XFER_BLKS (128 * 1024)
+#define MAX_XFER_SIZE (MAX_XFER_BLKS / VDC_DEFAULT_BLK_SIZE)
+#define MAX_RING_COOKIES ((MAX_XFER_BLKS / PAGE_SIZE) + 2)
+
#define WAITING_FOR_LINK_UP 0x01
#define WAITING_FOR_TX_SPACE 0x02
#define WAITING_FOR_GEN_CMD 0x04
@@ -450,7 +454,7 @@ static int __send_request(struct request *req)
{
struct vdc_port *port = req->rq_disk->private_data;
struct vio_dring_state *dr = &port->vio.drings[VIO_DRIVER_TX_RING];
- struct scatterlist sg[port->ring_cookies];
+ struct scatterlist sg[MAX_RING_COOKIES];
struct vdc_req_entry *rqe;
struct vio_disk_desc *desc;
unsigned int map_perm;
@@ -458,6 +462,9 @@ static int __send_request(struct request *req)
u64 len;
u8 op;

+ if (WARN_ON(port->ring_cookies > MAX_RING_COOKIES))
+ return -EINVAL;
+
map_perm = LDC_MAP_SHADOW | LDC_MAP_DIRECT | LDC_MAP_IO;

if (rq_data_dir(req) == READ) {
@@ -984,9 +991,8 @@ static int vdc_port_probe(struct vio_dev *vdev, const struct vio_device_id *id)
goto err_out_free_port;

port->vdisk_block_size = VDC_DEFAULT_BLK_SIZE;
- port->max_xfer_size = ((128 * 1024) / port->vdisk_block_size);
- port->ring_cookies = ((port->max_xfer_size *
- port->vdisk_block_size) / PAGE_SIZE) + 2;
+ port->max_xfer_size = MAX_XFER_SIZE;
+ port->ring_cookies = MAX_RING_COOKIES;

err = vio_ldc_alloc(&port->vio, &vdc_ldc_cfg, port);
if (err)
--
2.17.1

--
Kees Cook
Pixel Security

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