On Mon, 01 Feb 2016 11:26:57 +0100, Dmitry Vyukov wrote:
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
Looks like a race at closing virmidi device. Does the patch below fix it?
thanks,
Takashi
--- diff --git a/sound/core/seq/seq_virmidi.c b/sound/core/seq/seq_virmidi.c index 3da2d48610b3..f71aedfb408c 100644 --- a/sound/core/seq/seq_virmidi.c +++ b/sound/core/seq/seq_virmidi.c @@ -254,9 +254,13 @@ static int snd_virmidi_output_open(struct snd_rawmidi_substream *substream) */ static int snd_virmidi_input_close(struct snd_rawmidi_substream *substream) { + struct snd_virmidi_dev *rdev = substream->rmidi->private_data; struct snd_virmidi *vmidi = substream->runtime->private_data; - snd_midi_event_free(vmidi->parser); + + write_lock_irq(&rdev->filelist_lock); list_del(&vmidi->list); + write_unlock_irq(&rdev->filelist_lock); + snd_midi_event_free(vmidi->parser); substream->runtime->private_data = NULL; kfree(vmidi); return 0;