syzbot has found a reproducer for the following issue on:
HEAD commit: d3590ebf Merge tag 'audit-pr-20200729' of git://git.kernel.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1207e0b8900000 kernel config: https://syzkaller.appspot.com/x/.config?x=812bbfcb6ae2cd60 dashboard link: https://syzkaller.appspot.com/bug?extid=1a54a94bd32716796edd compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11b227f8900000
IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+1a54a94bd32716796edd@syzkaller.appspotmail.com
================================================================== BUG: KASAN: use-after-free in list_empty include/linux/list.h:282 [inline] BUG: KASAN: use-after-free in delete_and_unsubscribe_port+0x8b/0x450 sound/core/seq/seq_ports.c:530 Read of size 8 at addr ffff888098523060 by task syz-executor.0/7202
CPU: 1 PID: 7202 Comm: syz-executor.0 Not tainted 5.8.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1f0/0x31e lib/dump_stack.c:118 print_address_description+0x66/0x5a0 mm/kasan/report.c:383 __kasan_report mm/kasan/report.c:513 [inline] kasan_report+0x132/0x1d0 mm/kasan/report.c:530 list_empty include/linux/list.h:282 [inline] delete_and_unsubscribe_port+0x8b/0x450 sound/core/seq/seq_ports.c:530 snd_seq_port_disconnect+0x568/0x610 sound/core/seq/seq_ports.c:612 snd_seq_ioctl_unsubscribe_port+0x349/0x6c0 sound/core/seq/seq_clientmgr.c:1525 snd_seq_oss_midi_close+0x397/0x620 sound/core/seq/oss/seq_oss_midi.c:405 snd_seq_oss_synth_reset+0x335/0x8b0 sound/core/seq/oss/seq_oss_synth.c:406 snd_seq_oss_reset+0x5b/0x250 sound/core/seq/oss/seq_oss_init.c:435 snd_seq_oss_ioctl+0x5c2/0x1090 sound/core/seq/oss/seq_oss_ioctl.c:93 odev_ioctl+0x51/0x70 sound/core/seq/oss/seq_oss.c:174 vfs_ioctl fs/ioctl.c:48 [inline] ksys_ioctl fs/ioctl.c:753 [inline] __do_sys_ioctl fs/ioctl.c:762 [inline] __se_sys_ioctl+0xf9/0x160 fs/ioctl.c:760 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45c429 Code: 8d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 5b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f6e48930c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000000154c0 RCX: 000000000045c429 RDX: 0000000000000000 RSI: 0000000000005100 RDI: 0000000000000003 RBP: 000000000078bf38 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c R13: 00007ffe51b9d10f R14: 00007f6e489319c0 R15: 000000000078bf0c
Allocated by task 7202: save_stack mm/kasan/common.c:48 [inline] set_track mm/kasan/common.c:56 [inline] __kasan_kmalloc+0x103/0x140 mm/kasan/common.c:494 kmem_cache_alloc_trace+0x234/0x300 mm/slab.c:3551 kmalloc include/linux/slab.h:555 [inline] kzalloc include/linux/slab.h:669 [inline] snd_seq_port_connect+0x66/0x460 sound/core/seq/seq_ports.c:553 snd_seq_ioctl_subscribe_port+0x349/0x6c0 sound/core/seq/seq_clientmgr.c:1484 snd_seq_oss_midi_open+0x4db/0x830 sound/core/seq/oss/seq_oss_midi.c:364 snd_seq_oss_synth_setup_midi+0x108/0x510 sound/core/seq/oss/seq_oss_synth.c:269 snd_seq_oss_open+0x899/0xe90 sound/core/seq/oss/seq_oss_init.c:261 odev_open+0x5e/0x90 sound/core/seq/oss/seq_oss.c:125 chrdev_open+0x498/0x580 fs/char_dev.c:414 do_dentry_open+0x813/0x1070 fs/open.c:828 do_open fs/namei.c:3243 [inline] path_openat+0x278d/0x37f0 fs/namei.c:3360 do_filp_open+0x191/0x3a0 fs/namei.c:3387 do_sys_openat2+0x463/0x770 fs/open.c:1179 do_sys_open fs/open.c:1195 [inline] __do_sys_openat fs/open.c:1209 [inline] __se_sys_openat fs/open.c:1204 [inline] __x64_sys_openat+0x1c8/0x1f0 fs/open.c:1204 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 7203: save_stack mm/kasan/common.c:48 [inline] set_track mm/kasan/common.c:56 [inline] kasan_set_free_info mm/kasan/common.c:316 [inline] __kasan_slab_free+0x114/0x170 mm/kasan/common.c:455 __cache_free mm/slab.c:3426 [inline] kfree+0x10a/0x220 mm/slab.c:3757 snd_seq_port_disconnect+0x570/0x610 sound/core/seq/seq_ports.c:614 snd_seq_ioctl_unsubscribe_port+0x349/0x6c0 sound/core/seq/seq_clientmgr.c:1525 snd_seq_oss_midi_close+0x397/0x620 sound/core/seq/oss/seq_oss_midi.c:405 snd_seq_oss_synth_reset+0x335/0x8b0 sound/core/seq/oss/seq_oss_synth.c:406 snd_seq_oss_reset+0x5b/0x250 sound/core/seq/oss/seq_oss_init.c:435 snd_seq_oss_ioctl+0x5c2/0x1090 sound/core/seq/oss/seq_oss_ioctl.c:93 odev_ioctl+0x51/0x70 sound/core/seq/oss/seq_oss.c:174 vfs_ioctl fs/ioctl.c:48 [inline] ksys_ioctl fs/ioctl.c:753 [inline] __do_sys_ioctl fs/ioctl.c:762 [inline] __se_sys_ioctl+0xf9/0x160 fs/ioctl.c:760 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9
The buggy address belongs to the object at ffff888098523000 which belongs to the cache kmalloc-128 of size 128 The buggy address is located 96 bytes inside of 128-byte region [ffff888098523000, ffff888098523080) The buggy address belongs to the page: page:ffffea00026148c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0xfffe0000000200(slab) raw: 00fffe0000000200 ffffea0002613988 ffffea000262c648 ffff8880aa400700 raw: 0000000000000000 ffff888098523000 0000000100000010 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff888098522f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888098522f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888098523000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff888098523080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888098523100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================