[PATCH 4.14 065/124] termios, tty/tty_baudrate.c: fix buffer overrun

Greg Kroah-Hartman
2018-11-19T16:49:41Z

From: H. Peter Anvin <hpa@zytor.com>

commit 991a25194097006ec1e0d2e0814ff920e59e3465 upstream.

On architectures with CBAUDEX == 0 (Alpha and PowerPC), the code in tty_baudrate.c does
not do any limit checking on the tty_baudrate[] array, and in fact a
buffer overrun is possible on both architectures. Add a limit check to
prevent that situation.

This will be followed by a much bigger cleanup/simplification patch.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Requested-by: Cc: Johan Hovold <johan@kernel.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Eugene Syromiatnikov <esyr@redhat.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/tty/tty_baudrate.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/tty/tty_baudrate.c
+++ b/drivers/tty/tty_baudrate.c
@@ -76,7 +76,7 @@ speed_t tty_termios_baud_rate(struct kte
else
cbaud += 15;
}
- return baud_table[cbaud];
+ return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
}
EXPORT_SYMBOL(tty_termios_baud_rate);

@@ -112,7 +112,7 @@ speed_t tty_termios_input_baud_rate(stru
else
cbaud += 15;
}
- return baud_table[cbaud];
+ return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
#else
return tty_termios_baud_rate(termios);
#endif