diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2015-11-27 14:30:21 -0500 |
|---|---|---|
| committer | jenkins_ndg <jenkins_ndg@intel.com> | 2016-11-09 14:07:41 +0000 |
| commit | d63b2a33d38a3ce56d84157db11d9ddd86737cdd (patch) | |
| tree | 0887b9d2b550f41e62270c7d94cbccd1eb2bf325 | |
| parent | cb9051564bc92ff42fccdb2525f39a64adb9a591 (diff) | |
| download | x86-d63b2a33d38a3ce56d84157db11d9ddd86737cdd.tar.gz | |
tty: Prevent ldisc drivers from re-using stale tty fields
Line discipline drivers may mistakenly misuse ldisc-related fields
when initializing. For example, a failure to initialize tty->receive_room
in the N_GIGASET_M101 line discipline was recently found and fixed [1].
Now, the N_X25 line discipline has been discovered accessing the previous
line discipline's already-freed private data [2].
Harden the ldisc interface against misuse by initializing revelant
tty fields before instancing the new line discipline.
[1]
commit fd98e9419d8d622a4de91f76b306af6aa627aa9c
Author: Tilman Schmidt <tilman@imap.cc>
Date: Tue Jul 14 00:37:13 2015 +0200
isdn/gigaset: reset tty->receive_room when attaching ser_gigaset
[2] Report from Sasha Levin <sasha.levin@oracle.com>
[ 634.336761] ==================================================================
[ 634.338226] BUG: KASAN: use-after-free in x25_asy_open_tty+0x13d/0x490 at addr ffff8800a743efd0
[ 634.339558] Read of size 4 by task syzkaller_execu/8981
[ 634.340359] =============================================================================
[ 634.341598] BUG kmalloc-512 (Not tainted): kasan: bad access detected
...
[ 634.405018] Call Trace:
[ 634.405277] dump_stack (lib/dump_stack.c:52)
[ 634.405775] print_trailer (mm/slub.c:655)
[ 634.406361] object_err (mm/slub.c:662)
[ 634.406824] kasan_report_error (mm/kasan/report.c:138 mm/kasan/report.c:236)
[ 634.409581] __asan_report_load4_noabort (mm/kasan/report.c:279)
[ 634.411355] x25_asy_open_tty (drivers/net/wan/x25_asy.c:559 (discriminator 1))
[ 634.413997] tty_ldisc_open.isra.2 (drivers/tty/tty_ldisc.c:447)
[ 634.414549] tty_set_ldisc (drivers/tty/tty_ldisc.c:567)
[ 634.415057] tty_ioctl (drivers/tty/tty_io.c:2646 drivers/tty/tty_io.c:2879)
[ 634.423524] do_vfs_ioctl (fs/ioctl.c:43 fs/ioctl.c:607)
[ 634.427491] SyS_ioctl (fs/ioctl.c:622 fs/ioctl.c:613)
[ 634.427945] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:188)
Change-Id: I4a6357f3900762dea5542b2f38946a3db0d754d0
Tracked-On: https://jira01.devtools.intel.com/browse/AW-2339
Cc: Tilman Schmidt <tilman@imap.cc>
Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-on: https://android.intel.com/546407
Reviewed-by: Mahe, Erwan <erwan.mahe@intel.com>
Tested-by: Maalem, Saadi <saadi.maalem@intel.com>
Reviewed-by: Tasayco Loarte, VictorX <victorx.tasayco.loarte@intel.com>
Tested-by: Tasayco Loarte, VictorX <victorx.tasayco.loarte@intel.com>
Reviewed-by: Maalem, Saadi <saadi.maalem@intel.com>
| -rw-r--r-- | drivers/tty/tty_ldisc.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index d11ad0785316..95380f6acdb8 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -400,6 +400,10 @@ EXPORT_SYMBOL_GPL(tty_ldisc_flush); * they are not on hot paths so a little discipline won't do * any harm. * + * The line discipline-related tty_struct fields are reset to + * prevent the ldisc driver from re-using stale information for + * the new ldisc instance. + * * Locking: takes termios_mutex */ @@ -408,6 +412,9 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num) mutex_lock(&tty->termios_mutex); tty->termios.c_line = num; mutex_unlock(&tty->termios_mutex); + + tty->disc_data = NULL; + tty->receive_room = 0; } /** |