diff options
| author | DaeRyong Jeong <threeearcat@gmail.com> | 2018-05-01 00:27:04 +0900 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-05-14 13:52:35 +0200 |
| commit | b6da31b2c07c46f2dcad1d86caa835227a16d9ff (patch) | |
| tree | 3d1ad537c7587eea304b3821cfb7db3076bf16fc /drivers | |
| parent | 638a6f4ebeba82ad098fdfa4449011074d3e2673 (diff) | |
tty: Fix data race in tty_insert_flip_string_fixed_flag
Unlike normal serials, in pty layer, there is no guarantee that multiple
threads don't insert input characters at the same time. If it is happened,
tty_insert_flip_string_fixed_flag can be executed concurrently. This can
lead slab out-of-bounds write in tty_insert_flip_string_fixed_flag.
Call sequences are as follows.
CPU0 CPU1
n_tty_ioctl_helper n_tty_ioctl_helper
__start_tty tty_send_xchar
tty_wakeup pty_write
n_hdlc_tty_wakeup tty_insert_flip_string
n_hdlc_send_frames tty_insert_flip_string_fixed_flag
pty_write
tty_insert_flip_string
tty_insert_flip_string_fixed_flag
To fix the race, acquire port->lock in pty_write() before it inserts input
characters to tty buffer. It prevents multiple threads from inserting
input characters concurrently.
The crash log is as follows:
BUG: KASAN: slab-out-of-bounds in tty_insert_flip_string_fixed_flag+0xb5/
0x130 drivers/tty/tty_buffer.c:316 at addr ffff880114fcc121
Write of size 1792 by task syz-executor0/30017
CPU: 1 PID: 30017 Comm: syz-executor0 Not tainted 4.8.0 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014
0000000000000000 ffff88011638f888 ffffffff81694cc3 ffff88007d802140
ffff880114fcb300 ffff880114fcc300 ffff880114fcb300 ffff88011638f8b0
ffffffff8130075c ffff88011638f940 ffff88007d802140 ffff880194fcc121
Call Trace:
__dump_stack lib/dump_stack.c:15 [inline]
dump_stack+0xb3/0x110 lib/dump_stack.c:51
kasan_object_err+0x1c/0x70 mm/kasan/report.c:156
print_address_description mm/kasan/report.c:194 [inline]
kasan_report_error+0x1f7/0x4e0 mm/kasan/report.c:283
kasan_report+0x36/0x40 mm/kasan/report.c:303
check_memory_region_inline mm/kasan/kasan.c:292 [inline]
check_memory_region+0x13e/0x1a0 mm/kasan/kasan.c:299
memcpy+0x37/0x50 mm/kasan/kasan.c:335
tty_insert_flip_string_fixed_flag+0xb5/0x130 drivers/tty/tty_buffer.c:316
tty_insert_flip_string include/linux/tty_flip.h:35 [inline]
pty_write+0x7f/0xc0 drivers/tty/pty.c:115
n_hdlc_send_frames+0x1d4/0x3b0 drivers/tty/n_hdlc.c:419
n_hdlc_tty_wakeup+0x73/0xa0 drivers/tty/n_hdlc.c:496
tty_wakeup+0x92/0xb0 drivers/tty/tty_io.c:601
__start_tty.part.26+0x66/0x70 drivers/tty/tty_io.c:1018
__start_tty+0x34/0x40 drivers/tty/tty_io.c:1013
n_tty_ioctl_helper+0x146/0x1e0 drivers/tty/tty_ioctl.c:1138
n_hdlc_tty_ioctl+0xb3/0x2b0 drivers/tty/n_hdlc.c:794
tty_ioctl+0xa85/0x16d0 drivers/tty/tty_io.c:2992
vfs_ioctl fs/ioctl.c:43 [inline]
do_vfs_ioctl+0x13e/0xba0 fs/ioctl.c:679
SYSC_ioctl fs/ioctl.c:694 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
entry_SYSCALL_64_fastpath+0x1f/0xbd
Signed-off-by: DaeRyong Jeong <threeearcat@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/tty/pty.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c index 6c7151edd715..b0e2c4847a5d 100644 --- a/drivers/tty/pty.c +++ b/drivers/tty/pty.c @@ -110,16 +110,19 @@ static void pty_unthrottle(struct tty_struct *tty) static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c) { struct tty_struct *to = tty->link; + unsigned long flags; if (tty->stopped) return 0; if (c > 0) { + spin_lock_irqsave(&to->port->lock, flags); /* Stuff the data into the input queue of the other end */ c = tty_insert_flip_string(to->port, buf, c); /* And shovel */ if (c) tty_flip_buffer_push(to->port); + spin_unlock_irqrestore(&to->port->lock, flags); } return c; } |