bisecting fixing commit since c6db52a88798e5a0dfef80041ad4d33cc8cf04eb building syzkaller on 2420d1bcbcd9f5d5893c1aab8096cce81721dac2 testing commit c6db52a88798e5a0dfef80041ad4d33cc8cf04eb with gcc (GCC) 8.1.0 kernel signature: 8e8d06aee70603637271edc2167c49515192ac1aab7ea66028c8a2c6f4eb2cb3 run #0: crashed: KASAN: use-after-free Read in tasklet_action run #1: crashed: KASAN: use-after-free Read in bcm_can_tx run #2: crashed: KASAN: use-after-free Read in tasklet_action run #3: crashed: KASAN: use-after-free Read in tasklet_action run #4: crashed: KASAN: use-after-free Read in tasklet_action run #5: crashed: KASAN: use-after-free Read in bcm_can_tx run #6: crashed: KASAN: use-after-free Read in bcm_tx_start_timer run #7: crashed: KASAN: use-after-free Read in tasklet_action run #8: crashed: WARNING: ODEBUG bug in enqueue_hrtimer run #9: crashed: KASAN: use-after-free Read in tasklet_action testing current HEAD 1752938529c614a8ed4432ecce6ebc95d3b87207 testing commit 1752938529c614a8ed4432ecce6ebc95d3b87207 with gcc (GCC) 8.1.0 kernel signature: 0cb15ae6a79d40b378865538d83cfa5588cef2f0330a2f7de521652c3071631e run #0: crashed: KASAN: use-after-free Read in tasklet_action run #1: crashed: KASAN: use-after-free Read in bcm_can_tx run #2: crashed: KASAN: use-after-free Read in tasklet_action run #3: crashed: KASAN: use-after-free Read in tasklet_action run #4: crashed: KASAN: use-after-free Read in bcm_can_tx run #5: crashed: KASAN: use-after-free Read in tasklet_action run #6: crashed: KASAN: use-after-free Read in bcm_can_tx run #7: crashed: KASAN: use-after-free Read in tasklet_action run #8: crashed: KASAN: use-after-free Read in tasklet_action run #9: crashed: KASAN: use-after-free Read in tasklet_action revisions tested: 2, total time: 31m13.674797426s (build: 16m8.444337628s, test: 14m30.152965116s) the crash still happens on HEAD commit msg: Linux 4.14.213 crash: KASAN: use-after-free Read in tasklet_action ================================================================== BUG: KASAN: use-after-free in tasklet_action+0x2aa/0x360 kernel/softirq.c:506 Read of size 8 at addr ffff8881ded7dc10 by task syz-executor.5/24111 CPU: 1 PID: 24111 Comm: syz-executor.5 Not tainted 4.14.213-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/0x1f1 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/0x2d4 mm/kasan/report.c:409 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430 tasklet_action+0x2aa/0x360 kernel/softirq.c:506 __do_softirq+0x246/0x9b5 kernel/softirq.c:288 invoke_softirq kernel/softirq.c:368 [inline] irq_exit+0x15f/0x1a0 kernel/softirq.c:409 exiting_irq arch/x86/include/asm/apic.h:648 [inline] smp_apic_timer_interrupt+0x145/0x5d0 arch/x86/kernel/apic/apic.c:1102 apic_timer_interrupt+0x9a/0xa0 arch/x86/entry/entry_64.S:793 RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline] RIP: 0010:_raw_spin_unlock_irq+0x56/0x90 kernel/locking/spinlock.c:200 RSP: 0018:ffff8881d8da7d80 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10 RAX: dffffc0000000000 RBX: ffff8881f672b680 RCX: 0000000000000000 RDX: 1ffffffff0fe2bc3 RSI: 0000000000000001 RDI: ffffffff87f15e18 RBP: ffff8881d8da7d88 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881f2c2c280 R13: ffff8881e7be8600 R14: 0000000000000000 R15: ffff8881f2c2c6b8 finish_lock_switch kernel/sched/sched.h:1346 [inline] finish_task_switch+0x172/0x650 kernel/sched/core.c:2675 context_switch kernel/sched/core.c:2811 [inline] __schedule+0x82c/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 exit_to_usermode_loop+0x13c/0x190 arch/x86/entry/common.c:153 prepare_exit_to_usermode+0x16a/0x1b0 arch/x86/entry/common.c:199 retint_user+0x8/0x18 RIP: 0033:0x416661 RSP: 002b:00007ffe9df5b740 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff10 RAX: fffffffffffffff7 RBX: 0000000000000014 RCX: 0000000000416661 RDX: fffffffffffffff7 RSI: 0000000000000081 RDI: 0000000000000013 RBP: 0000000000000000 R08: 0000000000790700 R09: 0000000000000000 R10: 00007ffe9df5b660 R11: 0000000000000293 R12: 0000000000000001 R13: 00007ffe9df5b780 R14: 0000000000000000 R15: 00007ffe9df5b790 Allocated by task 24123: 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_trace+0x152/0x3f0 mm/slab.c:3618 kmalloc include/linux/slab.h:488 [inline] kzalloc include/linux/slab.h:661 [inline] bcm_tx_setup net/can/bcm.c:952 [inline] bcm_sendmsg+0x1994/0x4520 net/can/bcm.c:1388 sock_sendmsg_nosec net/socket.c:646 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:656 ___sys_sendmsg+0x625/0x920 net/socket.c:2062 __sys_sendmsg+0xc1/0x140 net/socket.c:2096 SYSC_sendmsg net/socket.c:2107 [inline] SyS_sendmsg+0xd/0x20 net/socket.c:2103 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb Freed by task 24118: 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 bcm_remove_op+0x1cd/0x240 net/can/bcm.c:781 bcm_release+0xe7/0x500 net/can/bcm.c:1540 __sock_release+0xc2/0x2a0 net/socket.c:602 sock_close+0x10/0x20 net/socket.c:1139 __fput+0x232/0x740 fs/file_table.c:210 ____fput+0x9/0x10 fs/file_table.c:244 task_work_run+0xe5/0x170 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x14a/0x190 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x416/0x5b0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x46/0xbb The buggy address belongs to the object at ffff8881ded7db40 which belongs to the cache kmalloc-1024 of size 1024 The buggy address is located 208 bytes inside of 1024-byte region [ffff8881ded7db40, ffff8881ded7df40) The buggy address belongs to the page: page:ffffea00077b5f00 count:1 mapcount:0 mapping:ffff8881ded7c040 index:0x0 compound_mapcount: 0 flags: 0x17ffe0000008100(slab|head) raw: 017ffe0000008100 ffff8881ded7c040 0000000000000000 0000000100000007 raw: ffffea00077dcb20 ffffea00077ae1a0 ffff8881f6000ac0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8881ded7db00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ffff8881ded7db80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8881ded7dc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8881ded7dc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881ded7dd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================