linux-kernel - [PATCH] char: pcmcia: fix possible array index out of bounds in set

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Date:   Fri, 21 May 2021 18:07:05 +0800
From:   Yu Kuai <yukuai3@...wei.com>
To:     <laforge@...monks.org>, <arnd@...db.de>,
        <gregkh@...uxfoundation.org>, <akpm@...l.org>
CC:     <linux-kernel@...r.kernel.org>, <yukuai3@...wei.com>,
        <yi.zhang@...wei.com>
Subject: [PATCH] char: pcmcia: fix possible array index out of bounds in set_protocol()

The length of array 'pts_reply' is 4, and the loop in set_protocol()
will access array element from 0 to num_bytes_read - 1. Thus if
io_read_num_rec_bytes() gets 'num_bytes_read' more than 4, it will
cause index out of bounds errors.

Fixes: c1986ee9bea3 ("[PATCH] New Omnikey Cardman 4000 driver")
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 drivers/char/pcmcia/cm4000_cs.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/char/pcmcia/cm4000_cs.c b/drivers/char/pcmcia/cm4000_cs.c
index 89681f07bc78..86b7c8e44198 100644
--- a/drivers/char/pcmcia/cm4000_cs.c
+++ b/drivers/char/pcmcia/cm4000_cs.c
@@ -564,16 +564,15 @@ static int set_protocol(struct cm4000_dev *dev, struct ptsreq *ptsreq)
 
 	/* Read PPS reply */
 	DEBUGP(5, dev, "Read PPS reply\n");
-	for (i = 0; i < num_bytes_read; i++) {
+	for (i = 0; i < 4; i++) {
 		xoutb(i, REG_BUF_ADDR(iobase));
 		pts_reply[i] = inb(REG_BUF_DATA(iobase));
 	}
 
 #ifdef CM4000_DEBUG
 	DEBUGP(2, dev, "PTSreply: ");
-	for (i = 0; i < num_bytes_read; i++) {
+	for (i = 0; i < 4; i++)
 		pr_debug("0x%.2x ", pts_reply[i]);
-	}
 	pr_debug("\n");
 #endif	/* CM4000_DEBUG */
 
-- 
2.25.4