bisecting fixing commit since 78d697fc93f98054e36a3ab76dca1a88802ba7be building syzkaller on 4a4e0509de520c7139ca2b5606712cbadc550db2 testing commit 78d697fc93f98054e36a3ab76dca1a88802ba7be with gcc (GCC) 8.1.0 kernel signature: e40eeda39e7ed6344ed151c50bdc91d8a5ba80219c810b33272485c489273fe5 run #0: crashed: KASAN: use-after-free Write in ex_handler_refcount 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 Read in l2cap_chan_close run #5: crashed: KASAN: use-after-free Write in ex_handler_refcount run #6: crashed: KASAN: use-after-free Write in ex_handler_refcount 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 Read in l2cap_chan_close testing current HEAD 050272a0423e68207fd2367831ae610680129062 testing commit 050272a0423e68207fd2367831ae610680129062 with gcc (GCC) 8.1.0 kernel signature: d714082d37104bcf6d459b543462bce50ee4cd2513cc0fddfbaee2486f8d95f4 run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close 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 Write in ex_handler_refcount run #6: crashed: KASAN: use-after-free Write in ex_handler_refcount 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 revisions tested: 2, total time: 24m56.460272963s (build: 17m32.360951607s, test: 6m20.983952888s) the crash still happens on HEAD commit msg: Linux 4.14.177 crash: KASAN: use-after-free Write in ex_handler_refcount IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready 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 ffff8880a91a8ad8 by task kworker/1:1/23 CPU: 1 PID: 23 Comm: kworker/1:1 Not tainted 4.14.177-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:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 print_address_description.cold.7+0x9/0x1c9 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report.cold.8+0x11a/0x2d3 mm/kasan/report.c:409 __asan_report_store4_noabort+0x17/0x20 mm/kasan/report.c:434 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:208 [inline] do_trap+0x63/0x240 arch/x86/kernel/traps.c:257 do_error_trap+0x159/0x310 arch/x86/kernel/traps.c:301 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:963 RIP: 0010:inat_get_avx_attribute+0x574c/0x7689 RSP: 0018:ffff8880a9ed7c80 EFLAGS: 00010296 RAX: ffffed10153daf77 RBX: 0000000000000080 RCX: ffff8880a91a8ad8 RDX: 1ffffffff0ec72cf RSI: 0000000000000000 RDI: ffff8880a91a8ac0 RBP: ffff8880a9ed7c80 R08: ffff8880a9ec8ed0 R09: 0000000000000938 R10: 0000000000000028 R11: ffff8880a9ec8600 R12: ffff8880a9dfea00 R13: ffff8880a9ed7d38 R14: ffff8880aed2f200 R15: ffff88808b242100 do_enable_set+0x468/0x870 net/bluetooth/6lowpan.c:1087 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2116 worker_thread+0xcc/0xee0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Allocated by task 3: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:551 kmem_cache_alloc_trace+0x152/0x7a0 mm/slab.c:3618 kmalloc include/linux/slab.h:488 [inline] kzalloc include/linux/slab.h:661 [inline] l2cap_chan_create+0x41/0x380 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+0x48f/0x870 net/bluetooth/6lowpan.c:1090 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2116 worker_thread+0xcc/0xee0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Freed by task 3: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3496 [inline] kfree+0xcc/0x270 mm/slab.c:3815 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+0x468/0x870 net/bluetooth/6lowpan.c:1087 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2116 worker_thread+0xcc/0xee0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 The buggy address belongs to the object at ffff8880a91a8ac0 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 24 bytes inside of 2048-byte region [ffff8880a91a8ac0, ffff8880a91a92c0) The buggy address belongs to the page: page:ffffea0002a46a00 count:1 mapcount:0 mapping:ffff8880a91a8240 index:0xffff8880a91a9340 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff8880a91a8240 ffff8880a91a9340 0000000100000002 raw: ffffea0002a39920 ffffea00022bd120 ffff8880aa800c40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a91a8980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a91a8a00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc >ffff8880a91a8a80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ^ ffff8880a91a8b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a91a8b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================