linux-kernel - [PATCH 3/3] Input: ims-pcu - Check record size in ims_pcu_flash

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Message-ID: <131fd1ae92c828ee9f4fa2de03d8c210ae1f3524.1748463049.git.dan.carpenter@linaro.org>
Date: Wed, 28 May 2025 23:22:24 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Kees Cook <kees@...nel.org>
Cc: Javier Carrasco <javier.carrasco.cruz@...il.com>,
	David Lechner <dlechner@...libre.com>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Erick Archer <erick.archer@...look.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] Input: ims-pcu - Check record size in
 ims_pcu_flash_firmware()

The "len" variable comes from the firmware and we generally do
trust firmware, but it's always better to double check.  If the "len"
is too large it could result in memory corruption when we do
"memcpy(fragment->data, rec->data, len);"

Fixes: 628329d52474 ("Input: add IMS Passenger Control Unit driver")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
Kees, this is a __counted_by() thing.  Would the checkers catch this?
We know the maximum valid length for "fragment" is and so it's maybe
possible to know that "fragment->len = len;" is too long?

 drivers/input/misc/ims-pcu.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/input/misc/ims-pcu.c b/drivers/input/misc/ims-pcu.c
index d9ee14b1f451..4581f1c53644 100644
--- a/drivers/input/misc/ims-pcu.c
+++ b/drivers/input/misc/ims-pcu.c
@@ -844,6 +844,12 @@ static int ims_pcu_flash_firmware(struct ims_pcu *pcu,
 		addr = be32_to_cpu(rec->addr) / 2;
 		len = be16_to_cpu(rec->len);
 
+		if (len > sizeof(pcu->cmd_buf) - 1 - sizeof(*fragment)) {
+			dev_err(pcu->dev,
+				"Invalid record length in firmware: %d\n", len);
+			return -EINVAL;
+		}
+
 		fragment = (void *)&pcu->cmd_buf[1];
 		put_unaligned_le32(addr, &fragment->addr);
 		fragment->len = len;
-- 
2.47.2