diff options
| author | Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> | 2021-04-15 09:22:22 +0900 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-04-22 12:01:26 +0200 |
| commit | c0070e1e60270f6a1e09442a9ab2335f3eaeaad2 (patch) | |
| tree | d292f1bf3d8524792f14786275489d9195fdb12f /drivers/char | |
| parent | f9f54983005cdd1060b85b16933677442139d88d (diff) | |
ttyprintk: Add TTY hangup callback.
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")
Link: https://lore.kernel.org/r/17e0652d-89b7-c8c0-fb53-e7566ac9add4@i-love.sakura.ne.jp
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/ttyprintk.c | 11 |
1 files changed, 11 insertions, 0 deletions
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 = { }; |