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authorSamuel Thibault <samuel.thibault@ens-lyon.org>2020-11-29 22:35:23 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-11-30 11:20:32 +0300
commitf0992098cadb4c9c6a00703b66cafe604e178fea (patch)
tree46ba746d25bb147727c739d61d1aaac35a7b40f3 /drivers/accessibility
parentb65054597872ce3aefbc6a666385eabdf9e288da (diff)
downloadlinux-f0992098cadb4c9c6a00703b66cafe604e178fea.tar.xz
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: stable@vger.kernel.org Reported-by: Shisong Qin <qinshisong1205@gmail.com> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org> Tested-by: Shisong Qin <qinshisong1205@gmail.com> Link: https://lore.kernel.org/r/20201129193523.hm3f6n5xrn6fiyyc@function Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/accessibility')
-rw-r--r--drivers/accessibility/speakup/spk_ttyio.c37
1 files changed, 23 insertions, 14 deletions
diff --git a/drivers/accessibility/speakup/spk_ttyio.c b/drivers/accessibility/speakup/spk_ttyio.c
index 669392f31d4e..6284aff434a1 100644
--- a/drivers/accessibility/speakup/spk_ttyio.c
+++ b/drivers/accessibility/speakup/spk_ttyio.c
@@ -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;
}