FAILED: patch "[PATCH] speakup: Reject setting the speakup line discipline outside" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Dec 9, 2020

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Stable branch Speakup console speech driver

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2020-12-09 15:52 UTC #0 lore raw

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f0992098cadb4c9c6a00703b66cafe604e178fea Mon Sep 17 00:00:00 2001
From: Samuel Thibault <[email protected]>
Date: Sun, 29 Nov 2020 20:35:23 +0100
Subject: [PATCH] speakup: Reject setting the speakup line discipline outside
of speakup

Speakup exposing a line discipline allows userland to try to use it, while it is deemed to be useless, and thus uselessly exposes potential bugs. One of them is simply that in such a case if the line sends data, spk_ttyio_receive_buf2 is called and crashes since spk_ttyio_synth is NULL.

This change restricts the use of the speakup line discipline to speakup drivers, thus avoiding such kind of issues altogether.

Cc [email protected]

Reported-by Shisong Qin <[email protected]>

Signed-off-by Samuel Thibault <[email protected]>

Tested-by Shisong Qin <[email protected]>

Link https://lore.kernel.org/r/20201129193523.hm3f6n5xrn6fiyyc@function open here

Signed-off-by Greg Kroah-Hartman <[email protected]>

drivers/accessibility/speakup/spk_ttyio.c +23 ~~-14~~

index 669392f31d4e..6284aff434a1 100644
@@ -47,27 +47,20 @@ static int spk_ttyio_ldisc_open(struct tty_struct *tty)
 {
 	struct spk_ldisc_data *ldisc_data;
 
+	if (tty != speakup_tty)
+		/* Somebody tried to use this line discipline outside speakup */
+		return -ENODEV;
+
 	if (!tty->ops->write)
 		return -EOPNOTSUPP;
 
-	mutex_lock(&speakup_tty_mutex);
-	if (speakup_tty) {
-		mutex_unlock(&speakup_tty_mutex);
-		return -EBUSY;
-	}
-	speakup_tty = tty;
-
 	ldisc_data = kmalloc(sizeof(*ldisc_data), GFP_KERNEL);
-	if (!ldisc_data) {
-		speakup_tty = NULL;
-		mutex_unlock(&speakup_tty_mutex);
+	if (!ldisc_data)
 		return -ENOMEM;
-	}
 
 	init_completion(&ldisc_data->completion);
 	ldisc_data->buf_free = true;
-	speakup_tty->disc_data = ldisc_data;
-	mutex_unlock(&speakup_tty_mutex);
+	tty->disc_data = ldisc_data;
 
 	return 0;
 }

@@ -191,9 +184,25 @@ static int spk_ttyio_initialise_ldisc(struct spk_synth *synth)
 
 	tty_unlock(tty);
 
+	mutex_lock(&speakup_tty_mutex);
+	speakup_tty = tty;
 	ret = tty_set_ldisc(tty, N_SPEAKUP);
 	if (ret)
-		pr_err("speakup: Failed to set N_SPEAKUP on tty\n");
+		speakup_tty = NULL;
+	mutex_unlock(&speakup_tty_mutex);
+
+	if (!ret)
+		/* Success */
+		return 0;
+
+	pr_err("speakup: Failed to set N_SPEAKUP on tty\n");
+
+	tty_lock(tty);
+	if (tty->ops->close)
+		tty->ops->close(tty, NULL);
+	tty_unlock(tty);
+
+	tty_kclose(tty);
 
 	return ret;
 }