bisecting fixing commit since 78d697fc93f98054e36a3ab76dca1a88802ba7be building syzkaller on 4a4e0509de520c7139ca2b5606712cbadc550db2 testing commit 78d697fc93f98054e36a3ab76dca1a88802ba7be with gcc (GCC) 8.1.0 kernel signature: 548b23e20f793d093c391b63a3999163871c28243faf96fef745255632fa175a 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 Read in l2cap_chan_close 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 Write in ex_handler_refcount run #8: crashed: KASAN: use-after-free Write in ex_handler_refcount run #9: crashed: KASAN: use-after-free Read in l2cap_chan_close testing current HEAD 4f68020fef1c6cf1b680ffb6481ac41379283ea3 testing commit 4f68020fef1c6cf1b680ffb6481ac41379283ea3 with gcc (GCC) 8.1.0 kernel signature: 8e36adb2656ca2aba38d24276dd333ef79b3630486d35ad93c26aa317717536a 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 Read in l2cap_chan_close run #7: crashed: KASAN: use-after-free Write in ex_handler_refcount 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: 23m43.741721213s (build: 17m5.375238791s, test: 6m2.292331249s) the crash still happens on HEAD commit msg: Linux 4.14.182 crash: KASAN: use-after-free Write in ex_handler_refcount IPv6: ADDRCONF(NETDEV_UP): batadv_slave_1: link is not ready 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 ffff88809e090258 by task kworker/1:3/3647 CPU: 1 PID: 3647 Comm: kworker/1:3 Not tainted 4.14.182-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:964 RIP: 0010:inat_get_avx_attribute+0x575a/0x76cc RSP: 0018:ffff8880a905fc80 EFLAGS: 00010296 RAX: ffffed101520bf77 RBX: 0000000000000080 RCX: ffff88809e090258 RDX: 1ffffffff0ec7477 RSI: 0000000000000000 RDI: ffff88809e090240 RBP: ffff8880a905fc80 R08: ffff8880a9690e50 R09: 00000000000023d6 R10: 0000000000000028 R11: ffff8880a9690580 R12: ffff88808eb44600 R13: ffff8880a905fd38 R14: ffff8880aed2f200 R15: ffff888084b2be00 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 3647: 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 ffff88809e090240 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 24 bytes inside of 2048-byte region [ffff88809e090240, ffff88809e090a40) The buggy address belongs to the page: page:ffffea0002782400 count:1 mapcount:0 mapping:ffff88809e090240 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff88809e090240 0000000000000000 0000000100000003 raw: ffffea00025f4220 ffffea00027fc7a0 ffff8880aa800c40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88809e090100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88809e090180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88809e090200: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ^ ffff88809e090280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809e090300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================