[PATCH 5.17 0713/1126] mxser: fix xmit_buf leak in activate when LSR == 0xff

Greg Kroah-Hartman
2022-04-05T08:37:16Z

From: Jiri Slaby <jslaby@suse.cz>

[ Upstream commit cd3a4907ee334b40d7aa880c7ab310b154fd5cd4 ]

When LSR is 0xff in ->activate() (rather unlike), we return an error.
Provided ->shutdown() is not called when ->activate() fails, nothing
actually frees the buffer in this case.

Fix this by properly freeing the buffer in a designated label. We jump
there also from the "!info->type" if now too.

Fixes: 6769140d3047 ("tty: mxser: use the tty_port_open method")
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220124071430.14907-6-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/mxser.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index c858aff721c4..fbb796f83753 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -744,6 +744,7 @@ static int mxser_activate(struct tty_port *port, struct tty_struct *tty)
struct mxser_port *info = container_of(port, struct mxser_port, port);
unsigned long page;
unsigned long flags;
+ int ret;

page = __get_free_page(GFP_KERNEL);
if (!page)
@@ -753,9 +754,9 @@ static int mxser_activate(struct tty_port *port, struct tty_struct *tty)

if (!info->type) {
set_bit(TTY_IO_ERROR, &tty->flags);
- free_page(page);
spin_unlock_irqrestore(&info->slock, flags);
- return 0;
+ ret = 0;
+ goto err_free_xmit;
}
info->port.xmit_buf = (unsigned char *) page;

@@ -775,8 +776,10 @@ static int mxser_activate(struct tty_port *port, struct tty_struct *tty)
if (capable(CAP_SYS_ADMIN)) {
set_bit(TTY_IO_ERROR, &tty->flags);
return 0;
- } else
- return -ENODEV;
+ }
+
+ ret = -ENODEV;
+ goto err_free_xmit;
}

/*
@@ -821,6 +824,10 @@ static int mxser_activate(struct tty_port *port, struct tty_struct *tty)
spin_unlock_irqrestore(&info->slock, flags);

return 0;
+err_free_xmit:
+ free_page(page);
+ info->port.xmit_buf = NULL;
+ return ret;
}

/*
--
2.34.1