linux-kernel - [PATCH v2 14/14] tty: n_tty: deduplicate copy code in n_tty_receive_buf_real

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20230827074147.2287-15-jirislaby@kernel.org>
Date:   Sun, 27 Aug 2023 09:41:47 +0200
From:   "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To:     gregkh@...uxfoundation.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Subject: [PATCH v2 14/14] tty: n_tty: deduplicate copy code in n_tty_receive_buf_real_raw()

The code is duplicated to perform the copy twice -- to handle buffer
wrap-around. Instead of the duplication, roll this into the loop.

(And add some blank lines around to have the code a bit more readable.)

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
---
 drivers/tty/n_tty.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index edf59f6fc669..6c9a408d67cd 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1528,19 +1528,18 @@ n_tty_receive_buf_real_raw(const struct tty_struct *tty, const u8 *cp,
 			   size_t count)
 {
 	struct n_tty_data *ldata = tty->disc_data;
-	size_t n, head;
-
-	head = MASK(ldata->read_head);
-	n = min(count, N_TTY_BUF_SIZE - head);
-	memcpy(read_buf_addr(ldata, head), cp, n);
-	ldata->read_head += n;
-	cp += n;
-	count -= n;
-
-	head = MASK(ldata->read_head);
-	n = min(count, N_TTY_BUF_SIZE - head);
-	memcpy(read_buf_addr(ldata, head), cp, n);
-	ldata->read_head += n;
+
+	/* handle buffer wrap-around by a loop */
+	for (unsigned int i = 0; i < 2; i++) {
+		size_t head = MASK(ldata->read_head);
+		size_t n = min(count, N_TTY_BUF_SIZE - head);
+
+		memcpy(read_buf_addr(ldata, head), cp, n);
+
+		ldata->read_head += n;
+		cp += n;
+		count -= n;
+	}
 }
 
 static void
-- 
2.42.0