bisecting fixing commit since 958e517f4e16952e9a2e2d58fd32d28ae4e23dda building syzkaller on fcdb12ba70875c410749932abf39160d19c753d9 testing commit 958e517f4e16952e9a2e2d58fd32d28ae4e23dda with gcc (GCC) 8.4.1 20210217 kernel signature: 901ac327a6a29f6d86b26bf0006c8db26b8d354387df4c6b11a3e38e4eeb2693 run #0: crashed: KASAN: use-after-free Read in tasklet_action run #1: crashed: KASAN: use-after-free Read in tasklet_action 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 tasklet_action run #6: crashed: KASAN: use-after-free Read in tasklet_action 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 run #10: crashed: KASAN: use-after-free Read in tasklet_action run #11: crashed: KASAN: use-after-free Read in tasklet_action run #12: crashed: KASAN: use-after-free Read in tasklet_action run #13: crashed: KASAN: use-after-free Read in tasklet_action run #14: crashed: KASAN: use-after-free Read in tasklet_action run #15: crashed: KASAN: use-after-free Read in tasklet_action run #16: crashed: KASAN: use-after-free Read in tasklet_action run #17: crashed: KASAN: use-after-free Read in tasklet_action run #18: crashed: KASAN: use-after-free Read in tasklet_action run #19: OK testing current HEAD 7d7d1c0ab3eb7c8d8f63a126535018007823b207 testing commit 7d7d1c0ab3eb7c8d8f63a126535018007823b207 with gcc (GCC) 8.4.1 20210217 kernel signature: a3149e8865f8a30f8548c37dbfdb5470ff96875d8eff42a44e582ddf804fe51e run #0: crashed: KASAN: use-after-free Read in tasklet_action run #1: crashed: KASAN: use-after-free Write in __tasklet_schedule 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 tasklet_action run #6: crashed: KASAN: use-after-free Read in tasklet_action 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: 36m50.076673172s (build: 15m46.52265836s, test: 20m40.410302829s) the crash still happens on HEAD commit msg: Linux 4.14.232 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 ffff8880b6126a10 by task syz-executor.1/11595 CPU: 1 PID: 11595 Comm: syz-executor.1 Not tainted 4.14.232-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/0x1e7 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 mm/kasan/report.c:409 [inline] kasan_report.cold.7+0x11a/0x2d3 mm/kasan/report.c:393 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430 tasklet_action+0x2aa/0x360 kernel/softirq.c:506 __do_softirq+0x247/0x9a2 kernel/softirq.c:288 do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1016 do_softirq kernel/softirq.c:332 [inline] do_softirq+0xee/0x160 kernel/softirq.c:319 __local_bh_enable_ip+0x130/0x150 kernel/softirq.c:185 __raw_write_unlock_bh include/linux/rwlock_api_smp.h:275 [inline] _raw_write_unlock_bh+0x30/0x40 kernel/locking/spinlock.c:352 sock_orphan include/net/sock.h:1715 [inline] bcm_release+0x3cf/0x500 net/can/bcm.c:1582 __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 RIP: 0033:0x466459 RSP: 002b:00007f893c287188 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 000000000056c008 RCX: 0000000000466459 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005 RBP: 00000000004bf9fb R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c008 R13: 00007ffc7139c35f R14: 00007f893c287300 R15: 0000000000022000 Allocated by task 11588: 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+0x1a3a/0x4680 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 11595: 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 ffff8880b6126940 which belongs to the cache kmalloc-1024 of size 1024 The buggy address is located 208 bytes inside of 1024-byte region [ffff8880b6126940, ffff8880b6126d40) The buggy address belongs to the page: page:ffffea0002d84980 count:1 mapcount:0 mapping:ffff8880b6126040 index:0xffff8880b61264c0 compound_mapcount: 0 flags: 0xfff00000008100(slab|head) raw: 00fff00000008100 ffff8880b6126040 ffff8880b61264c0 0000000100000005 raw: ffffea000283bb20 ffffea0002995d20 ffff88813fe60ac0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880b6126900: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ffff8880b6126980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8880b6126a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880b6126a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880b6126b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================