bisecting fixing commit since 0f1b4cb77d7f5a442b03f8ad597768b422e8ec58 building syzkaller on c59079a693ad1d89c782f7db14b9f1c5629e2abc testing commit 0f1b4cb77d7f5a442b03f8ad597768b422e8ec58 with gcc (GCC) 8.4.1 20210217 kernel signature: c8b9dd63466b601837d17dba15cb869b8af8281ca78af491e7661377fb84063f run #0: crashed: KASAN: use-after-free Read in nbd_put run #1: crashed: KASAN: use-after-free Read in nbd_put run #2: crashed: KASAN: use-after-free Read in nbd_put run #3: crashed: KASAN: use-after-free Write in ex_handler_refcount run #4: crashed: KASAN: use-after-free Read in nbd_put run #5: crashed: KASAN: use-after-free Read in nbd_put run #6: crashed: WARNING: refcount bug in nbd_put run #7: crashed: KASAN: use-after-free Read in nbd_put run #8: crashed: KASAN: use-after-free Read in nbd_put run #9: crashed: KASAN: use-after-free Read in nbd_put run #10: crashed: KASAN: use-after-free Read in nbd_put run #11: crashed: KASAN: use-after-free Read in nbd_put run #12: crashed: WARNING: refcount bug in nbd_put run #13: crashed: WARNING: refcount bug in nbd_put run #14: crashed: KASAN: use-after-free Read in nbd_put run #15: crashed: KASAN: use-after-free Read in nbd_put run #16: crashed: KASAN: use-after-free Read in nbd_put run #17: crashed: KASAN: use-after-free Read in nbd_put run #18: crashed: KASAN: use-after-free Read in nbd_put run #19: crashed: KASAN: use-after-free Write in ex_handler_refcount testing current HEAD 3c8c23092588a23bf1856a64f58c37f477a413be testing commit 3c8c23092588a23bf1856a64f58c37f477a413be with gcc (GCC) 8.4.1 20210217 kernel signature: 3c3cb85674cabd15222ab7f2640bfb52fc4dd363a378f00d415318de4247a3f7 run #0: crashed: KASAN: use-after-free Read in nbd_put run #1: crashed: KASAN: use-after-free Read in nbd_put run #2: crashed: WARNING: refcount bug in nbd_put run #3: crashed: KASAN: use-after-free Read in nbd_put run #4: crashed: KASAN: use-after-free Read in nbd_put run #5: crashed: KASAN: use-after-free Read in nbd_put run #6: crashed: WARNING: refcount bug in nbd_put run #7: crashed: KASAN: use-after-free Read in nbd_put run #8: crashed: KASAN: use-after-free Read in nbd_put run #9: crashed: KASAN: use-after-free Read in nbd_put revisions tested: 2, total time: 30m33.110717564s (build: 22m42.022982969s, test: 7m22.536765822s) the crash still happens on HEAD commit msg: Linux 4.19.190 crash: KASAN: use-after-free Read in nbd_put netlink: 4 bytes leftover after parsing attributes in process `syz-executor.1'. netlink: 4 bytes leftover after parsing attributes in process `syz-executor.2'. Bluetooth: hci5: command 0x0419 tx timeout syz-executor.2 (8465) used greatest stack depth: 22888 bytes left ================================================================== BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:21 [inline] BUG: KASAN: use-after-free in refcount_dec_not_one+0x72/0x160 lib/refcount.c:269 Read of size 4 at addr ffff88809e321b18 by task systemd-udevd/12451 CPU: 0 PID: 12451 Comm: systemd-udevd Not tainted 4.19.190-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+0x17c/0x226 lib/dump_stack.c:118 print_address_description.cold.6+0x9/0x211 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report mm/kasan/report.c:412 [inline] kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:396 check_memory_region_inline mm/kasan/kasan.c:260 [inline] check_memory_region+0x13c/0x1b0 mm/kasan/kasan.c:267 kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272 atomic_read include/asm-generic/atomic-instrumented.h:21 [inline] refcount_dec_not_one+0x72/0x160 lib/refcount.c:269 refcount_dec_and_mutex_lock+0x17/0x50 lib/refcount.c:308 nbd_put+0x1f/0x150 drivers/block/nbd.c:228 nbd_release+0xe1/0x140 drivers/block/nbd.c:1462 __blkdev_put+0x5fc/0x760 fs/block_dev.c:1819 blkdev_put+0x73/0x470 fs/block_dev.c:1881 blkdev_close+0x88/0xd0 fs/block_dev.c:1888 __fput+0x249/0x7f0 fs/file_table.c:278 ____fput+0x9/0x10 fs/file_table.c:309 task_work_run+0x108/0x180 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:193 [inline] exit_to_usermode_loop+0x185/0x1e0 arch/x86/entry/common.c:167 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f3e67fee270 Code: 73 01 c3 48 8b 0d 38 7d 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 59 c1 20 00 00 75 10 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 ee fb ff ff 48 89 04 24 RSP: 002b:00007ffdcc38af78 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007f3e67fee270 RDX: 000000000aba9500 RSI: 0000000000000000 RDI: 0000000000000007 RBP: 00007f3e68ea8710 R08: 0000000000000045 R09: 0000000000000018 R10: 0000560d81cd55f8 R11: 0000000000000246 R12: 0000000000000000 R13: 0000560d81cd9770 R14: 0000000000000003 R15: 000000000000000e Allocated by task 12441: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:553 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:538 kmem_cache_alloc_trace+0x152/0x3a0 mm/slab.c:3625 kmalloc include/linux/slab.h:515 [inline] kzalloc include/linux/slab.h:709 [inline] nbd_dev_add+0x4c/0x820 drivers/block/nbd.c:1627 nbd_genl_connect+0x3e8/0x1510 drivers/block/nbd.c:1773 genl_family_rcv_msg+0x599/0x1000 net/netlink/genetlink.c:602 genl_rcv_msg+0xa7/0x140 net/netlink/genetlink.c:627 netlink_rcv_skb+0x13e/0x3d0 net/netlink/af_netlink.c:2455 genl_rcv+0x23/0x40 net/netlink/genetlink.c:638 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x443/0x660 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1909 sock_sendmsg_nosec net/socket.c:622 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:632 ___sys_sendmsg+0x647/0x950 net/socket.c:2115 __sys_sendmsg+0xd9/0x180 net/socket.c:2153 __do_sys_sendmsg net/socket.c:2162 [inline] __se_sys_sendmsg net/socket.c:2160 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 12451: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x13c/0x220 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3503 [inline] kfree+0xcf/0x220 mm/slab.c:3822 nbd_dev_remove drivers/block/nbd.c:223 [inline] nbd_put drivers/block/nbd.c:231 [inline] nbd_put+0x111/0x150 drivers/block/nbd.c:226 nbd_config_put+0x539/0x7a0 drivers/block/nbd.c:1185 nbd_release+0xd9/0x140 drivers/block/nbd.c:1461 __blkdev_put+0x5fc/0x760 fs/block_dev.c:1819 blkdev_put+0x73/0x470 fs/block_dev.c:1881 blkdev_close+0x88/0xd0 fs/block_dev.c:1888 __fput+0x249/0x7f0 fs/file_table.c:278 ____fput+0x9/0x10 fs/file_table.c:309 task_work_run+0x108/0x180 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:193 [inline] exit_to_usermode_loop+0x185/0x1e0 arch/x86/entry/common.c:167 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe The buggy address belongs to the object at ffff88809e321a40 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 216 bytes inside of 512-byte region [ffff88809e321a40, ffff88809e321c40) The buggy address belongs to the page: page:ffffea000278c840 count:1 mapcount:0 mapping:ffff88813bff6940 index:0x0 flags: 0xfff00000000100(slab) raw: 00fff00000000100 ffffea000295e808 ffffea00029421c8 ffff88813bff6940 raw: 0000000000000000 ffff88809e321040 0000000100000006 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88809e321a00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ffff88809e321a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88809e321b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88809e321b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809e321c00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ==================================================================