[PATCH v6 2/5] scsi: mvumi: reject an out-of-range handshake frame length

[Yehyeong Lee <yhlee@isslab.korea.ac.kr>]

mvumi_hs_process_page() checksums and parses a handshake page using
frame_length from the page header, a u16 the firmware fills in, without
checking it against the HSP_MAX_SIZE buffer the page lives in.
mvumi_calculate_checksum() then walks frame_length bytes of frame_content
with an unsigned char loop counter, so a frame_length of 256 or more never
terminates and the probe path hangs; values between the buffer size and
255 read past the page.

Reject a frame_length that does not fit the handshake buffer before using
it.

Read frame_length once into a local and use it for both the bound check
and the checksum, so the device cannot change the value in the DMA page
between the two, and use READ_ONCE() so the single fetch is guaranteed
rather than left to the compiler.

Fixes: f0c568a478f0 ("[SCSI] mvumi: Add Marvell UMI driver")
Cc: stable@vger.kernel.org
Signed-off-by: Yehyeong Lee <yhlee@isslab.korea.ac.kr>
---
 drivers/scsi/mvumi.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/mvumi.c b/drivers/scsi/mvumi.c
index 38a92f8c25f5b..2378b676a7a78 100644
--- a/drivers/scsi/mvumi.c
+++ b/drivers/scsi/mvumi.c
@@ -1039,9 +1039,15 @@ static int mvumi_hs_process_page(struct mvumi_hba *mhba,
 {
 	struct mvumi_hs_page1 *hs_page1;
 	unsigned char page_checksum;
+	u16 frame_length = READ_ONCE(hs_header->frame_length);
 
-	page_checksum = mvumi_calculate_checksum(hs_header,
-						hs_header->frame_length);
+	if (frame_length > HSP_MAX_SIZE - sizeof(struct mvumi_hs_header)) {
+		dev_err(&mhba->pdev->dev, "invalid handshake frame length %d\n",
+			frame_length);
+		return -1;
+	}
+
+	page_checksum = mvumi_calculate_checksum(hs_header, frame_length);
 	if (page_checksum != hs_header->checksum) {
 		dev_err(&mhba->pdev->dev, "checksum error\n");
 		return -1;
-- 
2.43.0