diff options
| author | Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> | 2023-05-11 15:32:43 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-05-17 11:13:27 +0200 |
| commit | 3271859c2d2709515db4ad7a6cbdd3617da04405 (patch) | |
| tree | ecfffc52d104b7bb6ab690dda6f027dd330263cd /include/linux | |
| parent | f30f3391d089dc91aef91d08f4b04a6c0df2b067 (diff) | |
tty: Prevent writing chars during tcsetattr TCSADRAIN/FLUSH
If userspace races tcsetattr() with a write, the drained condition
might not be guaranteed by the kernel. There is a race window after
checking Tx is empty before tty_set_termios() takes termios_rwsem for
write. During that race window, more characters can be queued by a
racing writer.
Any ongoing transmission might produce garbage during HW's
->set_termios() call. The intent of TCSADRAIN/FLUSH seems to be
preventing such a character corruption. If those flags are set, take
tty's write lock to stop any writer before performing the lower layer
Tx empty check and wait for the pending characters to be sent (if any).
The initial wait for all-writers-done must be placed outside of tty's
write lock to avoid deadlock which makes it impossible to use
tty_wait_until_sent(). The write lock is retried if a racing write is
detected.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230317113318.31327-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 094fb49a2d0d6827c86d2e0840873e6db0c491d2)
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/tty.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h index d808ab9c9aff..487ce56b88e8 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -480,6 +480,8 @@ extern void __stop_tty(struct tty_struct *tty); extern void stop_tty(struct tty_struct *tty); extern void __start_tty(struct tty_struct *tty); extern void start_tty(struct tty_struct *tty); +void tty_write_unlock(struct tty_struct *tty); +int tty_write_lock(struct tty_struct *tty, int ndelay); extern int tty_register_driver(struct tty_driver *driver); extern int tty_unregister_driver(struct tty_driver *driver); extern struct device *tty_register_device(struct tty_driver *driver, |