linux-kernel - [PATCH 36/36] tty/vt: consolemap: walk the buffer only once in con_set_trans

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Message-Id: <20220607104946.18710-36-jslaby@suse.cz>
Date:   Tue,  7 Jun 2022 12:49:46 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     gregkh@...uxfoundation.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 36/36] tty/vt: consolemap: walk the buffer only once in con_set_trans_old()

Fetch the user data one by one (by get_user()) and fill in the local
buffer simultaneously. I.e. we no longer require to walk two buffers and
save thus 256 B from stack (whole ubuf).

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/tty/vt/consolemap.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
index f97f7ee6268b..fff97ae87e00 100644
--- a/drivers/tty/vt/consolemap.c
+++ b/drivers/tty/vt/consolemap.c
@@ -343,15 +343,15 @@ static void update_user_maps(void)
  */
 int con_set_trans_old(unsigned char __user * arg)
 {
-	int i;
 	unsigned short inbuf[E_TABSZ];
-	unsigned char ubuf[E_TABSZ];
-
-	if (copy_from_user(ubuf, arg, E_TABSZ))
-		return -EFAULT;
+	unsigned int i;
+	unsigned char ch;
 
-	for (i = 0; i < E_TABSZ ; i++)
-		inbuf[i] = UNI_DIRECT_BASE | ubuf[i];
+	for (i = 0; i < ARRAY_SIZE(inbuf); i++) {
+		if (get_user(ch, &arg[i]))
+			return -EFAULT;
+		inbuf[i] = UNI_DIRECT_BASE | ch;
+	}
 
 	console_lock();
 	memcpy(translations[USER_MAP], inbuf, sizeof(inbuf));
-- 
2.36.1