sound: use-after-free in snd_seq_deliver_single_event

Dmitry Vyukov
2016-02-01T10:27:20Z

Hello,

The following program triggers use-after-free in
snd_seq_deliver_single_event (run in a tight parallel loop):

// autogenerated by syzkaller (http://github.com/google/syzkaller)
#include <pthread.h>
#include <stdint.h>
#include <string.h>
#include <sys/syscall.h>
#include <unistd.h>

#ifndef SYS_mmap
#define SYS_mmap 9
#endif
#ifndef SYS_syz_open_dev
#define SYS_syz_open_dev 1000001
#endif
#ifndef SYS_ioctl
#define SYS_ioctl 16
#endif
#ifndef SYS_getpgrp
#define SYS_getpgrp 111
#endif
#ifndef SYS_migrate_pages
#define SYS_migrate_pages 256
#endif
#ifndef SYS_read
#define SYS_read 0
#endif
#ifndef SYS_write
#define SYS_write 1
#endif
#ifndef SYS_dup3
#define SYS_dup3 292
#endif

long r[59];

void* thr(void* arg)
{
switch ((long)arg) {
case 0:
r[0] = syscall(SYS_mmap, 0x20000000ul, 0x47000ul, 0x3ul, 0x32ul,
0xfffffffffffffffful, 0x0ul);
break;
case 1:
memcpy((void*)0x20000000,
"\x2f\x64\x65\x76\x2f\x73\x65\x71\x75\x65\x6e\x63\x65\x72",
14);
r[2] =
syscall(SYS_open, "/dev/sequencer", 0x2ul, 0, 0, 0);
break;
case 2:
r[3] = syscall(SYS_mmap, 0x20047000ul, 0x1000ul, 0x3ul, 0x32ul,
0xfffffffffffffffful, 0x0ul);
break;
case 3:
r[4] = syscall(SYS_ioctl, r[2], 0x540ful, 0x20047ffcul, 0, 0, 0);
if (r[4] != -1)
r[5] = *(uint32_t*)0x20047ffc;
break;
case 4:
r[6] = syscall(SYS_getpgrp, r[5], 0, 0, 0, 0, 0);
break;
case 5:
r[7] = syscall(SYS_mmap, 0x20047000ul, 0x1000ul, 0x3ul, 0x32ul,
0xfffffffffffffffful, 0x0ul);
break;
case 6:
r[8] = syscall(SYS_mmap, 0x20047000ul, 0x1000ul, 0x3ul, 0x32ul,
0xfffffffffffffffful, 0x0ul);
break;
case 7:
*(uint64_t*)0x20047000 = (uint64_t)0x5;
*(uint64_t*)0x20047000 = (uint64_t)0xfffffffffffffff8;
r[11] = syscall(SYS_migrate_pages, r[6], 0xfful, 0x20047000ul,
0x20047000ul, 0, 0);
break;
case 8:
memcpy((void*)0x20043684,
"\x2f\x64\x65\x76\x2f\x64\x6d\x6d\x69\x64\x69\x23", 12);
r[13] = syscall(SYS_open, "/dev/dmmidi2", 0x8a000ul, 0, 0, 0);
break;
case 9:
r[14] = syscall(SYS_read, r[13], 0x20045000ul, 0x36ul, 0, 0, 0);
break;
case 10:
*(uint8_t*)0x2000042c = (uint8_t)0x0;
*(uint8_t*)0x2000042d = (uint8_t)0x9cf;
*(uint8_t*)0x2000042e = (uint8_t)0x9;
*(uint8_t*)0x2000042f = (uint8_t)0x0;
*(uint64_t*)0x20000444 = (uint64_t)0x0;
*(uint64_t*)0x2000044c = (uint64_t)0x989680;
*(uint8_t*)0x20000454 = (uint8_t)0x2;
*(uint8_t*)0x20000455 = (uint8_t)0x100000000;
*(uint8_t*)0x20000456 = (uint8_t)0x8d;
*(uint8_t*)0x20000457 = (uint8_t)0x7;
*(uint8_t*)0x20000464 = (uint8_t)0x51b2;
*(uint8_t*)0x20000465 = (uint8_t)0xfffffffffffff15a;
*(uint8_t*)0x20000466 = (uint8_t)0x4;
*(uint8_t*)0x20000467 = (uint8_t)0x4;
*(uint32_t*)0x20000468 = (uint32_t)0xffffffff;
*(uint8_t*)0x2000046c = (uint8_t)0x5;
*(uint8_t*)0x2000046d = (uint8_t)0xfffffffffffffff8;
*(uint8_t*)0x2000046e = (uint8_t)0x401;
*(uint8_t*)0x2000046f = (uint8_t)0x5;
*(uint64_t*)0x20000484 = (uint64_t)0x4;
*(uint64_t*)0x2000048c = (uint64_t)0x0;
*(uint8_t*)0x20000494 = (uint8_t)0xc2c1;
*(uint8_t*)0x20000495 = (uint8_t)0x1;
*(uint8_t*)0x20000496 = (uint8_t)0x6b;
*(uint8_t*)0x20000497 = (uint8_t)0x6;
*(uint8_t*)0x200004a0 = (uint8_t)0xfffffffffffffffa;
*(uint8_t*)0x200004a1 = (uint8_t)0x81;
*(uint8_t*)0x200004a2 = (uint8_t)0x0;
*(uint8_t*)0x200004a3 = (uint8_t)0xa6;
*(uint8_t*)0x200004a4 = (uint8_t)0x400;
*(uint8_t*)0x200004a5 = (uint8_t)0x3ff;
*(uint8_t*)0x200004a6 = (uint8_t)0x8;
*(uint8_t*)0x200004a7 = (uint8_t)0x3;
*(uint64_t*)0x200004bc = (uint64_t)0x0;
*(uint64_t*)0x200004c4 = (uint64_t)0x0;
*(uint8_t*)0x200004cc = (uint8_t)0x9e;
*(uint8_t*)0x200004cd = (uint8_t)0x7ff;
*(uint8_t*)0x200004ce = (uint8_t)0x7fff;
*(uint8_t*)0x200004cf = (uint8_t)0x9;
*(uint8_t*)0x200004e0 = (uint8_t)0xa;
*(uint32_t*)0x200004e4 = (uint32_t)0x6;
*(uint32_t*)0x200004e8 = (uint32_t)0xffffffff;
r[57] = syscall(SYS_write, r[2], 0x2000042cul, 0x78ul, 0, 0, 0);
break;
case 11:
r[58] = syscall(SYS_dup3, r[13], r[2], 0x80000ul, 0, 0, 0);
break;
}
return 0;
}

int main()
{
long i;
pthread_t th[12];

memset(r, -1, sizeof(r));
for (i = 0; i < 12; i++) {
pthread_create(&th[i], 0, thr, (void*)i);
usleep(10000);
}
for (i = 0; i < 12; i++) {
pthread_create(&th[i], 0, thr, (void*)i);
if (i % 2 == 0)
usleep(10000);
}
usleep(100000);
return 0;
}

==================================================================
BUG: KASAN: use-after-free in do_raw_spin_lock+0x281/0x2b0 at addr
ffff88002abf1654
Read of size 4 by task syz-executor/13987
=============================================================================
BUG kmalloc-96 (Not tainted): kasan: bad access detected
-----------------------------------------------------------------------------

INFO: Allocated in snd_midi_event_new+0x73/0x200 age=10 cpu=0 pid=13996
[< none >] ___slab_alloc+0x564/0x5b0 mm/slub.c:2470
[< none >] __slab_alloc+0x66/0xc0 mm/slub.c:2499
[< inline >] slab_alloc_node mm/slub.c:2562
[< inline >] slab_alloc mm/slub.c:2604
[< none >] kmem_cache_alloc_trace+0x25c/0x300 mm/slub.c:2621
[< inline >] kmalloc include/linux/slab.h:463
[< inline >] kzalloc include/linux/slab.h:607
[< none >] snd_midi_event_new+0x73/0x200
sound/core/seq/seq_midi_event.c:120
[< none >] snd_virmidi_input_open+0xfd/0x380
sound/core/seq/seq_virmidi.c:214
[< none >] open_substream+0x3eb/0x780 sound/core/rawmidi.c:269
[< none >] rawmidi_open_priv+0x144/0x300 sound/core/rawmidi.c:312
[< none >] snd_rawmidi_open+0x3fb/0xa90 sound/core/rawmidi.c:416
[< none >] soundcore_open+0x30f/0x640 sound/sound_core.c:639
[< none >] chrdev_open+0x22a/0x4c0 fs/char_dev.c:388
[< none >] do_dentry_open+0x6a2/0xcb0 fs/open.c:736
[< none >] vfs_open+0x17b/0x1f0 fs/open.c:853
[< inline >] do_last fs/namei.c:3254
[< none >] path_openat+0xde9/0x5e30 fs/namei.c:3386
[< none >] do_filp_open+0x18e/0x250 fs/namei.c:3421
[< none >] do_sys_open+0x1fc/0x420 fs/open.c:1022
[< inline >] SYSC_open fs/open.c:1040
[< none >] SyS_open+0x2d/0x40 fs/open.c:1035

INFO: Freed in snd_midi_event_free+0x43/0x60 age=17 cpu=0 pid=13996
[< none >] __slab_free+0x1fc/0x320 mm/slub.c:2680
[< inline >] slab_free mm/slub.c:2835
[< none >] kfree+0x2ac/0x2c0 mm/slub.c:3664
[< none >] snd_midi_event_free+0x43/0x60
sound/core/seq/seq_midi_event.c:142
[< none >] snd_virmidi_input_close+0x87/0x120
sound/core/seq/seq_virmidi.c:261
[< none >] close_substream.part.14+0xda/0x540 sound/core/rawmidi.c:486
[< inline >] close_substream sound/core/rawmidi.c:514
[< none >] rawmidi_release_priv+0x1e4/0x250 sound/core/rawmidi.c:504
[< none >] snd_rawmidi_release+0x62/0xf0 sound/core/rawmidi.c:539
[< none >] __fput+0x236/0x780 fs/file_table.c:208
[< none >] ____fput+0x15/0x20 fs/file_table.c:244
[< none >] task_work_run+0x170/0x210 kernel/task_work.c:115
[< inline >] exit_task_work include/linux/task_work.h:21
[< none >] do_exit+0x8b5/0x2cb0 kernel/exit.c:748
[< none >] do_group_exit+0x108/0x330 kernel/exit.c:878
[< none >] get_signal+0x5e4/0x14f0 kernel/signal.c:2307
[< none >] do_signal+0x83/0x1c90 arch/x86/kernel/signal.c:712
[< none >] exit_to_usermode_loop+0x1a5/0x210
arch/x86/entry/common.c:247
[< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:282
[< none >] syscall_return_slowpath+0x2ba/0x340
arch/x86/entry/common.c:344

INFO: Slab 0xffffea0000aafc00 objects=28 used=11 fp=0xffff88002abf0470
flags=0x1fffc0000004080
INFO: Object 0xffff88002abf1630 @offset=5680 fp=0xffff88002abf06a8
CPU: 1 PID: 13987 Comm: syz-executor Tainted: G B 4.5.0-rc1+ #305
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
00000000ffffffff ffff880061aaf7d8 ffffffff82be11ad ffff88003e804900
ffff88002abf1630 ffff88002abf0000 ffff880061aaf808 ffffffff8175b454
ffff88003e804900 ffffea0000aafc00 ffff88002abf1630 000000000000000a

Call Trace:
[<ffffffff81764e3e>] __asan_report_load4_noabort+0x3e/0x40
mm/kasan/report.c:294
[< inline >] debug_spin_lock_before kernel/locking/spinlock_debug.c:83
[<ffffffff814663d1>] do_raw_spin_lock+0x281/0x2b0
kernel/locking/spinlock_debug.c:135
[< inline >] __raw_spin_lock_irqsave
include/linux/spinlock_api_smp.h:119
[<ffffffff86652b67>] _raw_spin_lock_irqsave+0xa7/0xd0
kernel/locking/spinlock.c:159
[<ffffffff852bb6a7>] snd_midi_event_decode+0x1f7/0x5c0
sound/core/seq/seq_midi_event.c:391
[< inline >] snd_virmidi_dev_receive_event
sound/core/seq/seq_virmidi.c:95
[<ffffffff852ce754>] snd_virmidi_event_input+0x214/0x310
sound/core/seq/seq_virmidi.c:133
[<ffffffff852a7934>]
snd_seq_deliver_single_event.constprop.11+0x3f4/0x740
sound/core/seq/seq_clientmgr.c:634
[<ffffffff852a7da2>] snd_seq_deliver_event+0x122/0x800
sound/core/seq/seq_clientmgr.c:828
[<ffffffff852a9186>] snd_seq_kernel_client_dispatch+0x126/0x170
sound/core/seq/seq_clientmgr.c:2401
[< inline >] snd_seq_oss_dispatch
sound/core/seq/oss/seq_oss_device.h:151
[<ffffffff852ca423>] snd_seq_oss_midi_reset+0x303/0x4a0
sound/core/seq/oss/seq_oss_midi.c:481
[<ffffffff852bd490>] snd_seq_oss_reset+0x130/0x260
sound/core/seq/oss/seq_oss_init.c:469
[<ffffffff852bd631>] snd_seq_oss_release+0x71/0x130
sound/core/seq/oss/seq_oss_init.c:425
[<ffffffff852bbcca>] odev_release+0x5a/0x80 sound/core/seq/oss/seq_oss.c:155
[<ffffffff817c0156>] __fput+0x236/0x780 fs/file_table.c:208
[<ffffffff817c0725>] ____fput+0x15/0x20 fs/file_table.c:244
[<ffffffff813b14e0>] task_work_run+0x170/0x210 kernel/task_work.c:115
[< inline >] tracehook_notify_resume include/linux/tracehook.h:191
[<ffffffff810066b1>] exit_to_usermode_loop+0x1d1/0x210
arch/x86/entry/common.c:251
[< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:282
[<ffffffff810084ea>] syscall_return_slowpath+0x2ba/0x340
arch/x86/entry/common.c:344
[<ffffffff86653322>] int_ret_from_sys_call+0x25/0x9f
arch/x86/entry/entry_64.S:281
==================================================================

general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN
Modules linked in:
CPU: 1 PID: 14982 Comm: syz-executor Tainted: G W 4.5.0-rc1+ #305
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88005e362f80 ti: ffff88005fba8000 task.ti: ffff88005fba8000
RIP: 0010:[<ffffffff852ce6d5>] [<ffffffff852ce6d5>]
snd_virmidi_event_input+0x195/0x310
RSP: 0018:ffff88005fbaf608 EFLAGS: 00010202
RAX: 1bd5a00000000023 RBX: dead000000000100 RCX: 0000000000000002
RDX: 0000000000000004 RSI: 0000000000000100 RDI: dead00000000011c
RBP: ffff88005fbaf6b8 R08: 0000000000000001 R09: 0000000000000000
R10: ffff88005e362f80 R11: ffff8800009fe110 R12: dffffc0000000000
R13: ffff88005fbaf900 R14: ffff8800009fe130 R15: 1ffff1000bf75ec6
FS: 00007fb93c201700(0000) GS:ffff88003ed00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000020045000 CR3: 000000005f9bd000 CR4: 00000000000006e0
Stack:
ffff8800009fe0f8 ffffed000bf75f20 ffff88005fbaf901 0000000000000000
ffff88003639fa50 0000000041b58ab3 ffffffff879486ce ffffffff852ce540
ffff88003639fa28 0000000000000000 ffff88003639fa38 ffff88005fbaf678
Call Trace:
[<ffffffff852a7934>]
snd_seq_deliver_single_event.constprop.11+0x3f4/0x740
sound/core/seq/seq_clientmgr.c:634
[<ffffffff852a7da2>] snd_seq_deliver_event+0x122/0x800
sound/core/seq/seq_clientmgr.c:828
[<ffffffff852a9186>] snd_seq_kernel_client_dispatch+0x126/0x170
sound/core/seq/seq_clientmgr.c:2401
[< inline >] snd_seq_oss_dispatch
sound/core/seq/oss/seq_oss_device.h:151
[<ffffffff852ca527>] snd_seq_oss_midi_reset+0x407/0x4a0
sound/core/seq/oss/seq_oss_midi.c:475
[<ffffffff852bd490>] snd_seq_oss_reset+0x130/0x260
sound/core/seq/oss/seq_oss_init.c:469
[<ffffffff852bd631>] snd_seq_oss_release+0x71/0x130
sound/core/seq/oss/seq_oss_init.c:425
[<ffffffff852bbcca>] odev_release+0x5a/0x80 sound/core/seq/oss/seq_oss.c:155
[<ffffffff817c0156>] __fput+0x236/0x780 fs/file_table.c:208
[<ffffffff817c0725>] ____fput+0x15/0x20 fs/file_table.c:244
[<ffffffff813b14e0>] task_work_run+0x170/0x210 kernel/task_work.c:115
[< inline >] exit_task_work include/linux/task_work.h:21
[<ffffffff8135ca55>] do_exit+0x8b5/0x2cb0 kernel/exit.c:748
[<ffffffff8135efc8>] do_group_exit+0x108/0x330 kernel/exit.c:878
[<ffffffff81382144>] get_signal+0x5e4/0x14f0 kernel/signal.c:2307
[<ffffffff811a0db3>] do_signal+0x83/0x1c90 arch/x86/kernel/signal.c:712
[<ffffffff81006685>] exit_to_usermode_loop+0x1a5/0x210
arch/x86/entry/common.c:247
[< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:282
[<ffffffff810084ea>] syscall_return_slowpath+0x2ba/0x340
arch/x86/entry/common.c:344
[<ffffffff86653322>] int_ret_from_sys_call+0x25/0x9f
arch/x86/entry/entry_64.S:281
Code: 3c 20 00 0f 85 31 01 00 00 48 8b 1b 49 39 de 0f 84 d9 00 00 00
e8 ec bb 29 fc 48 8d 7b 1c 48 89 f8 48 89 fa 48 c1 e8 03 83 e2 07 <42>
0f b6 04 20 38 d0 7f 08 84 c0 0f 85 3d 01 00 00 f6 43 1c 01
RIP [< inline >] snd_virmidi_dev_receive_event
sound/core/seq/seq_virmidi.c:88
RIP [<ffffffff852ce6d5>] snd_virmidi_event_input+0x195/0x310
sound/core/seq/seq_virmidi.c:133
RSP <ffff88005fbaf608>
---[ end trace 35fa82e449e91fba ]---
Fixing recursive fault but reboot is needed!

On commit 26cd83670f2f5a3d5b5514a1f7d96567cdb9558b.