bisecting fixing commit since b499cf4b3a901e87e1f933df04abf69b54de4457 building syzkaller on 5be3a391ba78f7f11b725cee6783880974b9895a testing commit b499cf4b3a901e87e1f933df04abf69b54de4457 with gcc (GCC) 8.1.0 kernel signature: 32a2e750b6d3c056a89f65787bb8fa02c3ce29fb15cf2f88eca01c7ba2b2bc5f run #0: crashed: KASAN: use-after-free Write in ex_handler_refcount run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close run #3: crashed: KASAN: use-after-free Write in ex_handler_refcount run #4: crashed: KASAN: use-after-free Write in ex_handler_refcount run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close run #9: crashed: KASAN: use-after-free Write in ex_handler_refcount testing current HEAD 84920cc7fbe10e838689e8e1437dfd18d6e54a2c testing commit 84920cc7fbe10e838689e8e1437dfd18d6e54a2c with gcc (GCC) 8.1.0 kernel signature: a204a560c7209991f6e54a6039b76c2ecd9086c54e3ecea5df7d2f6780a58c62 run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close run #1: crashed: KASAN: use-after-free Write in ex_handler_refcount run #2: crashed: KASAN: use-after-free Write in ex_handler_refcount run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close run #4: crashed: KASAN: use-after-free Write in ex_handler_refcount run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close run #6: crashed: KASAN: use-after-free Write in ex_handler_refcount run #7: crashed: KASAN: use-after-free Write in ex_handler_refcount run #8: crashed: KASAN: use-after-free Write in ex_handler_refcount run #9: OK revisions tested: 2, total time: 35m31.638399376s (build: 18m40.962202648s, test: 15m15.204289507s) the crash still happens on HEAD commit msg: Linux 4.19.121 crash: KASAN: use-after-free Write in ex_handler_refcount batman_adv: batadv0: Interface activated: batadv_slave_1 IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready ================================================================== BUG: KASAN: use-after-free in ex_handler_refcount+0x141/0x180 arch/x86/mm/extable.c:49 Write of size 4 at addr ffff8880a95e9498 by task kworker/0:2/3392 CPU: 0 PID: 3392 Comm: kworker/0:2 Not tainted 4.19.121-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events do_enable_set Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x123/0x177 lib/dump_stack.c:118 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412 __asan_report_store4_noabort+0x17/0x20 mm/kasan/report.c:437 ex_handler_refcount+0x141/0x180 arch/x86/mm/extable.c:49 fixup_exception+0x7c/0xb3 arch/x86/mm/extable.c:197 do_trap_no_signal arch/x86/kernel/traps.c:209 [inline] do_trap+0x63/0x240 arch/x86/kernel/traps.c:258 do_error_trap+0x189/0x350 arch/x86/kernel/traps.c:303 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1037 RIP: 0010:csum_partial_copy_generic+0x63ef/0x8385 Code: 0b 48 8d 8f 80 00 00 00 0f 0b 48 8d 8b 80 00 00 00 0f 0b 48 8d 0f 0f 0b 48 8d 0f 0f 0b 48 8d 8f b8 02 00 00 0f 0b 48 8d 4f 18 <0f> 0b 48 8d 8f b8 02 00 00 0f 0b 48 8d 4b 18 0f 0b 48 8d 4b 18 0f RSP: 0018:ffff88809b24fc40 EFLAGS: 00010296 RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffff8880a95e9498 RDX: 1ffffffff0f9aca3 RSI: 0000000000000000 RDI: ffff8880a95e9480 RBP: ffff88809b24fc40 R08: fffffbfff1210981 R09: fffffbfff1210980 R10: fffffbfff1210980 R11: ffffffff89084c03 R12: ffff88809b24fd30 R13: ffff88809b24fcb0 R14: ffff88809b24fcb0 R15: ffff88809b24fcb0 do_enable_set+0x48a/0x8b0 net/bluetooth/6lowpan.c:1087 process_one_work+0x830/0x1670 kernel/workqueue.c:2155 worker_thread+0x85/0xb60 kernel/workqueue.c:2298 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Allocated by task 3392: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553 kmem_cache_alloc_trace+0x152/0x740 mm/slab.c:3625 kmalloc include/linux/slab.h:515 [inline] kzalloc include/linux/slab.h:709 [inline] l2cap_chan_create+0x41/0x340 net/bluetooth/l2cap_core.c:441 chan_create+0xa/0xc0 net/bluetooth/6lowpan.c:652 bt_6lowpan_listen net/bluetooth/6lowpan.c:971 [inline] do_enable_set+0x4af/0x8b0 net/bluetooth/6lowpan.c:1090 process_one_work+0x830/0x1670 kernel/workqueue.c:2155 worker_thread+0x85/0xb60 kernel/workqueue.c:2298 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Freed by task 7555: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x102/0x150 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 l2cap_chan_destroy+0x132/0x1a0 net/bluetooth/l2cap_core.c:479 kref_put include/linux/kref.h:70 [inline] l2cap_chan_put+0x1e/0x20 net/bluetooth/l2cap_core.c:493 do_enable_set+0x48a/0x8b0 net/bluetooth/6lowpan.c:1087 process_one_work+0x830/0x1670 kernel/workqueue.c:2155 worker_thread+0x85/0xb60 kernel/workqueue.c:2298 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 The buggy address belongs to the object at ffff8880a95e9480 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 24 bytes inside of 2048-byte region [ffff8880a95e9480, ffff8880a95e9c80) The buggy address belongs to the page: page:ffffea0002a57a00 count:1 mapcount:0 mapping:ffff88812c29cc40 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffffea00023bd188 ffffea0002a4f108 ffff88812c29cc40 raw: 0000000000000000 ffff8880a95e8380 0000000100000003 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a95e9380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8880a95e9400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff8880a95e9480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880a95e9500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a95e9580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================