[PATCH] remoteproc: virtio: fix uninitialized buffer use in rproc_virtio_get()

[Kery Qi <qikeyu2017@gmail.com>]

rproc_virtio_get() returns early on out-of-bounds access without touching
the caller-provided buffer. Callers of virtio config accessors commonly
pass stack storage and do not get an error code back, so stale/uninit
bytes may be consumed as device configuration, leading to unpredictable
behavior and potentially leaking stack data if later exposed.

Always clear the destination buffer, reject offsets past config_len, and
clamp the read length to the available config bytes before copying.

Fixes: 92b38f851470 ("remoteproc: support virtio config space.")
Signed-off-by: Kery Qi <qikeyu2017@gmail.com>
---
 drivers/remoteproc/remoteproc_virtio.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c
index c5d46a878149..8fa8c8a86b4b 100644
--- a/drivers/remoteproc/remoteproc_virtio.c
+++ b/drivers/remoteproc/remoteproc_virtio.c
@@ -298,10 +298,13 @@ static void rproc_virtio_get(struct virtio_device *vdev, unsigned int offset,
 	rsc = (void *)rvdev->rproc->table_ptr + rvdev->rsc_offset;
 	cfg = &rsc->vring[rsc->num_of_vrings];
 
-	if (offset + len > rsc->config_len || offset + len < len) {
-		dev_err(&vdev->dev, "rproc_virtio_get: access out of bounds\n");
+	memset(buf, 0, len);
+
+	if (offset > rsc->config_len)
 		return;
-	}
+
+		if (len > rsc->config_len - offset)
+			len = rsc->config_len - offset;
 
 	memcpy(buf, cfg + offset, len);
 }
-- 
2.34.1