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authorTetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>2021-04-15 09:22:22 +0900
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-04-22 12:01:26 +0200
commitc0070e1e60270f6a1e09442a9ab2335f3eaeaad2 (patch)
treed292f1bf3d8524792f14786275489d9195fdb12f /drivers/char
parentf9f54983005cdd1060b85b16933677442139d88d (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.c11
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 = { };