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android_kernel_samsung_a7y1.../drivers/tty
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Jiri Slaby a09da7215c vt: selection, push sel_lock up 
commit e8c75a30a23c6ba63f4ef6895cbf41fd42f21aa2 upstream.

sel_lock cannot nest in the console lock. Thanks to syzkaller, the
kernel states firmly:

> WARNING: possible circular locking dependency detected
> 5.6.0-rc3-syzkaller #0 Not tainted
> ------------------------------------------------------
> syz-executor.4/20336 is trying to acquire lock:
> ffff8880a2e952a0 (&tty->termios_rwsem){++++}, at: tty_unthrottle+0x22/0x100 drivers/tty/tty_ioctl.c:136
>
> but task is already holding lock:
> ffffffff89462e70 (sel_lock){+.+.}, at: paste_selection+0x118/0x470 drivers/tty/vt/selection.c:374
>
> which lock already depends on the new lock.
>
> the existing dependency chain (in reverse order) is:
>
> -> #2 (sel_lock){+.+.}:
>        mutex_lock_nested+0x1b/0x30 kernel/locking/mutex.c:1118
>        set_selection_kernel+0x3b8/0x18a0 drivers/tty/vt/selection.c:217
>        set_selection_user+0x63/0x80 drivers/tty/vt/selection.c:181
>        tioclinux+0x103/0x530 drivers/tty/vt/vt.c:3050
>        vt_ioctl+0x3f1/0x3a30 drivers/tty/vt/vt_ioctl.c:364

This is ioctl(TIOCL_SETSEL).
Locks held on the path: console_lock -> sel_lock

> -> #1 (console_lock){+.+.}:
>        console_lock+0x46/0x70 kernel/printk/printk.c:2289
>        con_flush_chars+0x50/0x650 drivers/tty/vt/vt.c:3223
>        n_tty_write+0xeae/0x1200 drivers/tty/n_tty.c:2350
>        do_tty_write drivers/tty/tty_io.c:962 [inline]
>        tty_write+0x5a1/0x950 drivers/tty/tty_io.c:1046

This is write().
Locks held on the path: termios_rwsem -> console_lock

> -> #0 (&tty->termios_rwsem){++++}:
>        down_write+0x57/0x140 kernel/locking/rwsem.c:1534
>        tty_unthrottle+0x22/0x100 drivers/tty/tty_ioctl.c:136
>        mkiss_receive_buf+0x12aa/0x1340 drivers/net/hamradio/mkiss.c:902
>        tty_ldisc_receive_buf+0x12f/0x170 drivers/tty/tty_buffer.c:465
>        paste_selection+0x346/0x470 drivers/tty/vt/selection.c:389
>        tioclinux+0x121/0x530 drivers/tty/vt/vt.c:3055
>        vt_ioctl+0x3f1/0x3a30 drivers/tty/vt/vt_ioctl.c:364

This is ioctl(TIOCL_PASTESEL).
Locks held on the path: sel_lock -> termios_rwsem

> other info that might help us debug this:
>
> Chain exists of:
>   &tty->termios_rwsem --> console_lock --> sel_lock

Clearly. From the above, we have:
 console_lock -> sel_lock
 sel_lock -> termios_rwsem
 termios_rwsem -> console_lock

Fix this by reversing the console_lock -> sel_lock dependency in
ioctl(TIOCL_SETSEL). First, lock sel_lock, then console_lock.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: syzbot+26183d9746e62da329b8@syzkaller.appspotmail.com
Fixes: 07e6124a1a46 ("vt: selection, close sel_buffer race")
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200228115406.5735-2-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-04-07 14:10:27 +02:00
..
hvc powerpc/pseries/hvconsole: Fix stack overread via udbg 2020-04-07 13:24:58 +02:00
ipwireless tty: ipwireless: Fix potential NULL pointer dereference 2020-04-07 13:40:15 +02:00
serial serial: ar933x_uart: set UART_CS_{RX,TX}_READY_ORIDE 2020-04-07 14:09:52 +02:00
vt vt: selection, push sel_lock up 2020-04-07 14:10:27 +02:00
amiserial.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
bfin_jtag_comm.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
cyclades.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
ehv_bytechan.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
goldfish.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
isicom.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
Kconfig tty: ldisc: add sysctl to prevent autoloading of ldiscs 2020-04-06 15:07:28 +02:00
Makefile A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
metag_da.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
mips_ejtag_fdc.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
moxa.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
moxa.h A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
mxser.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
mxser.h A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
n_gsm.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
n_hdlc.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
n_r3964.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
n_tracerouter.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
n_tracesink.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
n_tracesink.h A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
n_tty.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
nozomi.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
pty.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
rocket_int.h A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
rocket.c tty: rocket: fix incorrect forward declaration of 'rp_init()' 2020-04-06 19:21:10 +02:00
rocket.h A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
synclink_gt.c synclink_gt(): fix compat_ioctl() 2020-04-07 12:34:19 +02:00
synclink.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
synclinkmp.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
sysrq.c sysrq: Remove duplicated sysrq message 2020-04-07 14:04:26 +02:00
tty_audit.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
tty_buffer.c tty: increase the default flip buffer limit to 2*640K 2020-04-06 14:52:07 +02:00
tty_io.c tty: ldisc: add sysctl to prevent autoloading of ldiscs 2020-04-06 15:07:28 +02:00
tty_ioctl.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
tty_ldisc.c tty: ldisc: add sysctl to prevent autoloading of ldiscs 2020-04-06 15:07:28 +02:00
tty_ldsem.c tty/ldsem, locking/rwsem: Add missing ACQUIRE to read_failed sleep loop 2020-04-06 20:39:18 +02:00
tty_mutex.c A750FXXU4CTBC 2020-03-27 21:51:54 +05:30
tty_port.c tty: always relink the port 2020-04-07 13:32:54 +02:00