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| author | Samuel Thibault <samuel.thibault@ens-lyon.org> | 2020-11-29 20:35:23 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-11-30 09:20:32 +0100 |
| commit | f0992098cadb4c9c6a00703b66cafe604e178fea (patch) | |
| tree | 46ba746d25bb147727c739d61d1aaac35a7b40f3 /drivers/accessibility | |
| parent | Linux 5.10-rc6 (diff) | |
| download | linux-f0992098cadb4c9c6a00703b66cafe604e178fea.tar.xz linux-f0992098cadb4c9c6a00703b66cafe604e178fea.zip | |
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.c | 37 |
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; } |