bisecting fixing commit since 3f2ecb86cb909da0b9157fd2952ad79924cbe5ae building syzkaller on bca53db974f570410921f59b8c2c59a3d263cb44 testing commit 3f2ecb86cb909da0b9157fd2952ad79924cbe5ae with gcc (GCC) 8.1.0 kernel signature: 75647a5e8980484d792adf839814eaae9b6e2a2141fc12753b0265178c629e88 run #0: crashed: WARNING in md_ioctl run #1: crashed: WARNING in md_ioctl run #2: crashed: WARNING in md_ioctl run #3: crashed: KASAN: use-after-free Read in disk_unblock_events run #4: crashed: WARNING in md_ioctl run #5: crashed: KASAN: use-after-free Read in disk_unblock_events run #6: crashed: WARNING in md_ioctl run #7: crashed: WARNING in md_ioctl run #8: crashed: KASAN: use-after-free Read in disk_unblock_events run #9: crashed: WARNING in md_ioctl testing current HEAD 2d2791fce891fc20709232d49a6bae075b9a77f8 testing commit 2d2791fce891fc20709232d49a6bae075b9a77f8 with gcc (GCC) 8.1.0 kernel signature: 961aebf2532cc4951499d9cda04d0d91517e50246fab6439a45bb92afa5e5043 all runs: crashed: KASAN: use-after-free Read in disk_unblock_events revisions tested: 2, total time: 21m45.651927282s (build: 15m50.467499378s, test: 5m27.977364107s) the crash still happens on HEAD commit msg: Linux 4.14.217 crash: KASAN: use-after-free Read in disk_unblock_events md: md1 stopped. md: md1 stopped. md: md1 stopped. md: md1 stopped. ================================================================== BUG: KASAN: use-after-free in disk_unblock_events+0x42/0x50 block/genhd.c:1647 Read of size 8 at addr ffff8880b3500608 by task syz-executor.0/11195 CPU: 1 PID: 11195 Comm: syz-executor.0 Not tainted 4.14.217-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x14b/0x1e7 lib/dump_stack.c:58 print_address_description.cold.6+0x9/0x1ca mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report.cold.7+0x11a/0x2d3 mm/kasan/report.c:409 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430 md: md1 stopped. disk_unblock_events+0x42/0x50 block/genhd.c:1647 __blkdev_get+0x6ef/0xff0 fs/block_dev.c:1556 blkdev_get+0x265/0x890 fs/block_dev.c:1611 blkdev_open+0x19f/0x200 fs/block_dev.c:1772 do_dentry_open+0x3e4/0xde0 fs/open.c:777 vfs_open+0xfc/0x240 fs/open.c:888 do_last fs/namei.c:3428 [inline] path_openat+0xb73/0x27a0 fs/namei.c:3569 do_filp_open+0x16b/0x220 fs/namei.c:3603 do_sys_open+0x1c2/0x340 fs/open.c:1081 SYSC_openat fs/open.c:1108 [inline] SyS_openat+0xf/0x20 fs/open.c:1102 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x45e159 RSP: 002b:00007f73403d6c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000045e159 RDX: 0000000000000000 RSI: 00000000200020c0 RDI: ffffffffffffff9c RBP: 000000000119c070 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119c034 R13: 00007ffd34c420ef R14: 00007f73403d79c0 R15: 000000000119c034 Allocated by task 11210: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack mm/kasan/kasan.c:447 [inline] set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:551 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:536 kmem_cache_alloc_node_trace+0x151/0x3f0 mm/slab.c:3661 kmalloc_node include/linux/slab.h:526 [inline] kzalloc_node include/linux/slab.h:672 [inline] alloc_disk_node+0x5e/0x380 block/genhd.c:1390 alloc_disk+0xe/0x10 block/genhd.c:1374 md_alloc+0x1e0/0x7b0 drivers/md/md.c:5332 md_probe+0x17/0x20 drivers/md/md.c:5389 kobj_lookup+0x20a/0x410 drivers/base/map.c:124 get_gendisk+0x2d/0x1d0 block/genhd.c:788 __blkdev_get+0x3d4/0xff0 fs/block_dev.c:1449 blkdev_get+0x265/0x890 fs/block_dev.c:1611 blkdev_open+0x19f/0x200 fs/block_dev.c:1772 do_dentry_open+0x3e4/0xde0 fs/open.c:777 vfs_open+0xfc/0x240 fs/open.c:888 do_last fs/namei.c:3428 [inline] path_openat+0xb73/0x27a0 fs/namei.c:3569 do_filp_open+0x16b/0x220 fs/namei.c:3603 do_sys_open+0x1c2/0x340 fs/open.c:1081 SYSC_openat fs/open.c:1108 [inline] SyS_openat+0xf/0x20 fs/open.c:1102 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb Freed by task 11195: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack mm/kasan/kasan.c:447 [inline] set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0xab/0x190 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3496 [inline] kfree+0xcc/0x270 mm/slab.c:3815 disk_release+0x215/0x290 block/genhd.c:1233 device_release+0xd7/0x170 drivers/base/core.c:831 kobject_cleanup lib/kobject.c:646 [inline] kobject_release lib/kobject.c:675 [inline] kref_put include/linux/kref.h:70 [inline] kobject_put+0x14f/0x3d0 lib/kobject.c:692 put_disk+0x15/0x20 block/genhd.c:1455 __blkdev_get+0x65c/0xff0 fs/block_dev.c:1549 blkdev_get+0x265/0x890 fs/block_dev.c:1611 blkdev_open+0x19f/0x200 fs/block_dev.c:1772 do_dentry_open+0x3e4/0xde0 fs/open.c:777 vfs_open+0xfc/0x240 fs/open.c:888 do_last fs/namei.c:3428 [inline] path_openat+0xb73/0x27a0 fs/namei.c:3569 do_filp_open+0x16b/0x220 fs/namei.c:3603 do_sys_open+0x1c2/0x340 fs/open.c:1081 SYSC_openat fs/open.c:1108 [inline] SyS_openat+0xf/0x20 fs/open.c:1102 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb The buggy address belongs to the object at ffff8880b3500080 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 1416 bytes inside of 2048-byte region [ffff8880b3500080, ffff8880b3500880) The buggy address belongs to the page: page:ffffea0002cd4000 count:1 mapcount:0 mapping:ffff8880b3500080 index:0x0 compound_mapcount: 0 flags: 0xfff00000008100(slab|head) raw: 00fff00000008100 ffff8880b3500080 0000000000000000 0000000100000003 raw: ffffea0002cda4a0 ffffea000257c320 ffff88813fe64c40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880b3500500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880b3500580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8880b3500600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880b3500680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880b3500700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================