linux-kernel - [PATCH] rapidio: potential overflow in riocm_ch

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Message-ID: <YLX6p+NXg2w+UqRq@mwanda>
Date:   Tue, 1 Jun 2021 12:15:19 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Matt Porter <mporter@...nel.crashing.org>
Cc:     Alexandre Bounine <alex.bou9@...il.com>,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] rapidio: potential overflow in riocm_ch_send()

The "buf" variable has "len" bytes, and the size is controlled by the
user in cm_chan_msg_send().  If the length is fewer than sizeof(*hdr)
then it could lead to memory corruption.

Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
Strictly speaking the last two bytes of length are reserved and not
written to but it's simpler and better to check "< sizeof(*hdr)" instead
of "< sizeof(*hdr) - 2".  This is better for future proofing.

 drivers/rapidio/rio_cm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/rapidio/rio_cm.c b/drivers/rapidio/rio_cm.c
index db4c265287ae..5c332b9867e1 100644
--- a/drivers/rapidio/rio_cm.c
+++ b/drivers/rapidio/rio_cm.c
@@ -784,7 +784,8 @@ static int riocm_ch_send(u16 ch_id, void *buf, int len)
 	struct rio_ch_chan_hdr *hdr;
 	int ret;
 
-	if (buf == NULL || ch_id == 0 || len == 0 || len > RIO_MAX_MSG_SIZE)
+	if (buf == NULL || ch_id == 0 ||
+	    len < sizeof(*hdr) || len > RIO_MAX_MSG_SIZE)
 		return -EINVAL;
 
 	ch = riocm_get_channel(ch_id);
-- 
2.30.2