bisecting fixing commit since c6db52a88798e5a0dfef80041ad4d33cc8cf04eb building syzkaller on 2420d1bcbcd9f5d5893c1aab8096cce81721dac2 testing commit c6db52a88798e5a0dfef80041ad4d33cc8cf04eb with gcc (GCC) 8.1.0 kernel signature: d1e5fe414be47b6d78bf5ec9ed615939ebfc5946dd265d36b60d694c2955e7f2 run #0: crashed: KASAN: use-after-free Read in tasklet_action run #1: crashed: WARNING: ODEBUG bug in enqueue_hrtimer 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 tasklet_action run #7: crashed: KASAN: use-after-free Read in hrtimer_debug_hint run #8: crashed: KASAN: use-after-free Read in bcm_can_tx run #9: crashed: KASAN: use-after-free Read in bcm_can_tx testing current HEAD d7e78d08fa77acdea351c8f628f49ca9a0e1029a testing commit d7e78d08fa77acdea351c8f628f49ca9a0e1029a with gcc (GCC) 8.1.0 kernel signature: 9b6ba8b8b59f1fae441174aa92931ae361ac080d3ad30ba56a28384033babc74 run #0: crashed: WARNING: ODEBUG bug in enqueue_hrtimer run #1: crashed: KASAN: use-after-free Write in __tasklet_schedule run #2: crashed: KASAN: use-after-free Read in bcm_can_tx run #3: crashed: KASAN: use-after-free Read in bcm_can_tx 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: WARNING: ODEBUG bug in enqueue_hrtimer run #8: crashed: KASAN: use-after-free Read in bcm_can_tx run #9: crashed: KASAN: use-after-free Read in bcm_can_tx revisions tested: 2, total time: 35m3.182048915s (build: 19m39.297246435s, test: 13m58.718932018s) the crash still happens on HEAD commit msg: Linux 4.14.195 crash: KASAN: use-after-free Read in bcm_can_tx ================================================================== BUG: KASAN: use-after-free in bcm_can_tx+0x4b7/0x640 net/can/bcm.c:312 Read of size 4 at addr ffff8880942da610 by task syz-executor.2/6464 CPU: 0 PID: 6464 Comm: syz-executor.2 Not tainted 4.14.195-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_load4_noabort+0x14/0x20 mm/kasan/report.c:429 bcm_can_tx+0x4b7/0x640 net/can/bcm.c:312 bcm_tx_timeout_tsklet+0xed/0x260 net/can/bcm.c:422 tasklet_action+0x19e/0x360 kernel/softirq.c:513 __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 include/linux/spinlock_api_smp.h:150 [inline] RIP: 0010:_raw_spin_unlock+0x1/0x50 kernel/locking/spinlock.c:184 RSP: 0018:ffff88809496fae0 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10 RAX: dffffc0000000000 RBX: 1ffff1101292df6a RCX: 0000000000000000 RDX: 1ffff11042a9117f RSI: ffff88821543d05e RDI: ffff88809a54ce80 RBP: ffff88809496fbd8 R08: 0000000000000400 R09: 0000000000000000 R10: 0000000000000050 R11: ffff888094146040 R12: ffff88809a54a240 R13: ffffffff88b26b70 R14: 000000000000a000 R15: ffff888215488980 ext4_evict_inode+0xcb1/0x14a0 fs/ext4/inode.c:341 evict+0x29c/0x590 fs/inode.c:555 iput_final fs/inode.c:1524 [inline] iput+0x3ac/0x810 fs/inode.c:1551 do_unlinkat+0x44e/0x640 fs/namei.c:4098 SYSC_unlink fs/namei.c:4139 [inline] SyS_unlink+0x11/0x20 fs/namei.c:4137 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x45c897 RSP: 002b:00007fffb1104bc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000057 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000045c897 RDX: 00007fffb1104be0 RSI: 00007fffb1104be0 RDI: 00007fffb1104c70 RBP: 00000000000014c5 R08: 0000000000000000 R09: 000000000000000d R10: 0000000000000006 R11: 0000000000000246 R12: 00007fffb1105d00 R13: 00000000010a7940 R14: 0000000000000000 R15: 00007fffb1105d00 Allocated by task 10360: 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 10358: 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 ffff8880942da4c0 which belongs to the cache kmalloc-1024 of size 1024 The buggy address is located 336 bytes inside of 1024-byte region [ffff8880942da4c0, ffff8880942da8c0) The buggy address belongs to the page: page:ffffea000250b680 count:1 mapcount:0 mapping:ffff8880942da040 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff8880942da040 0000000000000000 0000000100000007 raw: ffffea000291f2a0 ffffea0002854ca0 ffff8880aa800ac0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880942da500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880942da580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8880942da600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880942da680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880942da700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================