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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2024-04-23 19:33:39 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-06-27 14:49:05 +0300 |
| commit | 287b569a5b914903ba7c438a3c0dbc3410ebb409 (patch) | |
| tree | 872d3b5f1e120817c6ccb7df987eaaa61cf873fe /include/linux | |
| parent | a94a56004082df6f2106356f5497d274a10ff109 (diff) | |
| download | linux-287b569a5b914903ba7c438a3c0dbc3410ebb409.tar.xz | |
tty: add the option to have a tty reject a new ldisc
[ Upstream commit 6bd23e0c2bb6c65d4f5754d1456bc9a4427fc59b ]
... and use it to limit the virtual terminals to just N_TTY. They are
kind of special, and in particular, the "con_write()" routine violates
the "writes cannot sleep" rule that some ldiscs rely on.
This avoids the
BUG: sleeping function called from invalid context at kernel/printk/printk.c:2659
when N_GSM has been attached to a virtual console, and gsmld_write()
calls con_write() while holding a spinlock, and con_write() then tries
to get the console lock.
Tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Daniel Starke <daniel.starke@siemens.com>
Reported-by: syzbot <syzbot+dbac96d8e73b61aa559c@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=dbac96d8e73b61aa559c
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20240423163339.59780-1-torvalds@linux-foundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/tty_driver.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h index 18beff0cec1a..b4f99f6a5385 100644 --- a/include/linux/tty_driver.h +++ b/include/linux/tty_driver.h @@ -155,6 +155,13 @@ struct serial_struct; * * Optional. Called under the @tty->termios_rwsem. May sleep. * + * @ldisc_ok: ``int ()(struct tty_struct *tty, int ldisc)`` + * + * This routine allows the @tty driver to decide if it can deal + * with a particular @ldisc. + * + * Optional. Called under the @tty->ldisc_sem and @tty->termios_rwsem. + * * @set_ldisc: ``void ()(struct tty_struct *tty)`` * * This routine allows the @tty driver to be notified when the device's @@ -373,6 +380,7 @@ struct tty_operations { void (*hangup)(struct tty_struct *tty); int (*break_ctl)(struct tty_struct *tty, int state); void (*flush_buffer)(struct tty_struct *tty); + int (*ldisc_ok)(struct tty_struct *tty, int ldisc); void (*set_ldisc)(struct tty_struct *tty); void (*wait_until_sent)(struct tty_struct *tty, int timeout); void (*send_xchar)(struct tty_struct *tty, char ch); |