diff options
| author | Daniel Starke <daniel.starke@siemens.com> | 2022-07-01 09:16:52 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-07-01 11:07:40 +0300 |
| commit | 32dd59f96924f45e33bc79854f7a00679c0fa28e (patch) | |
| tree | c45bdc462f2dfa290fb83f8a675e05b34463229e /drivers/tty/n_gsm.c | |
| parent | 4fae831b3a71fc5a44cc5c7d0b8c1267ee7659f5 (diff) | |
| download | linux-32dd59f96924f45e33bc79854f7a00679c0fa28e.tar.xz | |
tty: n_gsm: fix race condition in gsmld_write()
The function may be used by the user directly and also by the n_gsm
internal functions. They can lead into a race condition which results in
interleaved frames if both are writing at the same time. The receiving side
is not able to decode those interleaved frames correctly.
Add a lock around the low side tty write to avoid race conditions and frame
interleaving between user originated writes and n_gsm writes.
Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220701061652.39604-9-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/n_gsm.c')
| -rw-r--r-- | drivers/tty/n_gsm.c | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 39359274096d..9a3d7db33394 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2859,11 +2859,24 @@ static ssize_t gsmld_read(struct tty_struct *tty, struct file *file, static ssize_t gsmld_write(struct tty_struct *tty, struct file *file, const unsigned char *buf, size_t nr) { - int space = tty_write_room(tty); + struct gsm_mux *gsm = tty->disc_data; + unsigned long flags; + int space; + int ret; + + if (!gsm) + return -ENODEV; + + ret = -ENOBUFS; + spin_lock_irqsave(&gsm->tx_lock, flags); + space = tty_write_room(tty); if (space >= nr) - return tty->ops->write(tty, buf, nr); - set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); - return -ENOBUFS; + ret = tty->ops->write(tty, buf, nr); + else + set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); + spin_unlock_irqrestore(&gsm->tx_lock, flags); + + return ret; } /** |