From: "Samo Pogačnik" <samo_pogacnik@t-2.net>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jirislaby@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
John Ogness <john.ogness@linutronix.de>,
linux-kernel@vger.kernel.org,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: [PATCH] ttyprintk: Add TTY hangup callback.
Date: Sun, 18 Apr 2021 13:16:05 +0200 [thread overview]
Message-ID: <8043d41d48a0f4f13bd891b4c3e9ad28c76b430e.camel@t-2.net> (raw)
In-Reply-To: <17e0652d-89b7-c8c0-fb53-e7566ac9add4@i-love.sakura.ne.jp>
Dne 15.04.2021 (čet) ob 09:22 +0900 je Tetsuo Handa napisal(a):
> syzbot is reporting hung task due to flood of
>
> tty_warn(tty, "%s: tty->count = 1 port count = %d\n", __func__,
> port->count);
>
> message [1], for ioctl(TIOCVHANGUP) prevents tty_port_close() from
> decrementing port->count due to tty_hung_up_p() == true.
>
> ----------
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <sys/ioctl.h>
> #include <unistd.h>
>
> int main(int argc, char *argv[])
> {
> int i;
> int fd[10];
>
> for (i = 0; i < 10; i++)
> fd[i] = open("/dev/ttyprintk", O_WRONLY);
> ioctl(fd[0], TIOCVHANGUP);
> for (i = 0; i < 10; i++)
> close(fd[i]);
> close(open("/dev/ttyprintk", O_WRONLY));
> return 0;
> }
> ----------
>
> When TTY hangup happens, port->count needs to be reset via
> "struct tty_operations"->hangup callback.
>
> [1]
> https://syzkaller.appspot.com/bug?id=39ea6caa479af471183997376dc7e90bc7d64a6a
>
> Reported-by: syzbot <syzbot+43e93968b964e369db0b@syzkaller.appspotmail.com>
> Reported-by: syzbot <syzbot+3ed715090790806d8b18@syzkaller.appspotmail.com>
> Tested-by: syzbot <syzbot+43e93968b964e369db0b@syzkaller.appspotmail.com>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Fixes: 24b4b67d17c308aa ("add ttyprintk driver")
> ---
> drivers/char/ttyprintk.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
> index 6a0059e508e3..93f5d11c830b 100644
> --- a/drivers/char/ttyprintk.c
> +++ b/drivers/char/ttyprintk.c
> @@ -158,12 +158,23 @@ static int tpk_ioctl(struct tty_struct *tty,
> return 0;
> }
>
> +/*
> + * TTY operations hangup function.
> + */
> +static void tpk_hangup(struct tty_struct *tty)
> +{
> + struct ttyprintk_port *tpkp = tty->driver_data;
> +
> + tty_port_hangup(&tpkp->port);
> +}
> +
> static const struct tty_operations ttyprintk_ops = {
> .open = tpk_open,
> .close = tpk_close,
> .write = tpk_write,
> .write_room = tpk_write_room,
> .ioctl = tpk_ioctl,
> + .hangup = tpk_hangup,
> };
>
> static const struct tty_port_operations null_ops = { };
Using the supplied test code, i've tested the patch on my desktop running the
5.4 kernel. After applying the patch, the kernel warnings like "ttyprintk:
tty_port_close_start: tty->count = 1 port count = 11" do not appear any more,
when the test code is run.
I think the patch is ok.
best regards, Samo
next prev parent reply other threads:[~2021-04-18 11:17 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-03 4:14 [PATCH] tty: use printk_safe context at tty_msg() Tetsuo Handa
2021-04-03 6:52 ` kernel test robot
2021-04-03 10:11 ` [PATCH] printk: Make multiple inclusion of kernel/printk/internal.h safe Tetsuo Handa
2021-04-06 4:51 ` [PATCH] tty: use printk_safe context at tty_msg() Jiri Slaby
2021-04-06 5:31 ` Tetsuo Handa
2021-04-06 7:10 ` Greg Kroah-Hartman
2021-04-06 11:16 ` Tetsuo Handa
2021-04-06 13:42 ` Greg Kroah-Hartman
2021-04-06 15:10 ` Petr Mladek
2021-04-06 16:22 ` Tetsuo Handa
2021-04-06 19:10 ` Greg Kroah-Hartman
2021-04-07 9:20 ` Petr Mladek
2021-04-07 13:26 ` [PATCH v2] tty: use printk_deferred() " Tetsuo Handa
2021-04-07 13:48 ` Greg Kroah-Hartman
2021-04-07 14:24 ` Tetsuo Handa
2021-04-12 10:39 ` How to handle concurrent access to /dev/ttyprintk ? Tetsuo Handa
2021-04-12 10:44 ` Greg Kroah-Hartman
2021-04-12 11:25 ` Tetsuo Handa
2021-04-12 12:04 ` Greg Kroah-Hartman
2021-04-14 0:45 ` Tetsuo Handa
2021-04-14 11:11 ` Tetsuo Handa
2021-04-14 16:15 ` Samo Pogačnik
2021-04-15 0:22 ` [PATCH] ttyprintk: Add TTY hangup callback Tetsuo Handa
2021-04-18 11:16 ` Samo Pogačnik [this message]
2021-04-22 10:02 ` Greg Kroah-Hartman
2021-04-23 4:22 ` Jiri Slaby
2021-04-23 9:55 ` Samo Pogačnik
2021-04-23 10:12 ` Tetsuo Handa
2021-04-23 19:47 ` Samo Pogačnik
2021-04-24 1:16 ` Tetsuo Handa
2021-04-24 9:57 ` Samo Pogačnik
2021-04-26 10:00 ` Petr Mladek
2021-04-26 16:42 ` Samo Pogačnik
2021-04-27 10:08 ` Petr Mladek
2021-04-27 11:31 ` Samo Pogačnik
2021-04-23 10:28 ` Jiri Slaby
2021-04-23 12:23 ` [PATCH] ttyprintk: Add TTY port shutdown callback Samo Pogačnik
2021-04-12 12:41 ` How to handle concurrent access to /dev/ttyprintk ? Samo Pogačnik
2021-04-13 9:41 ` Petr Mladek
2021-04-13 11:10 ` Samo Pogačnik
2021-04-13 14:32 ` Petr Mladek
2021-04-13 15:22 ` Samo Pogačnik
2021-04-14 17:36 ` Petr Mladek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=8043d41d48a0f4f13bd891b4c3e9ad28c76b430e.camel@t-2.net \
--to=samo_pogacnik@t-2.net \
--cc=gregkh@linuxfoundation.org \
--cc=jirislaby@kernel.org \
--cc=john.ogness@linutronix.de \
--cc=linux-kernel@vger.kernel.org \
--cc=penguin-kernel@i-love.sakura.ne.jp \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=sergey.senozhatsky@gmail.com \
--cc=syzkaller-bugs@googlegroups.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).