bisecting fixing commit since cbfa1702aaf69b2311ea1b35e04f113c48368c67 building syzkaller on 4a77ae0bdc5cd75ebe88ce7c896aae6bbf457a29 testing commit cbfa1702aaf69b2311ea1b35e04f113c48368c67 with gcc (GCC) 8.1.0 kernel signature: 2869ab8a4202683f8db25ed60aba65dd8e2a95db8015e0c3a831ec3303032fb2 all runs: crashed: KASAN: use-after-free Read in tasklet_action testing current HEAD e98f3c4269fda898b913259a7d9b60fb38269869 testing commit e98f3c4269fda898b913259a7d9b60fb38269869 with gcc (GCC) 8.1.0 kernel signature: 8ca77ebb9f384c0c654eb79637d73e1a99f9c5328193286dcc0fcf7f35fa7cad all runs: crashed: KASAN: use-after-free Read in tasklet_action revisions tested: 2, total time: 33m21.832333373s (build: 16m21.273752443s, test: 16m17.351603646s) the crash still happens on HEAD commit msg: Linux 4.14.205 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 ffff8880a0885750 by task syz-executor.2/8594 CPU: 0 PID: 8594 Comm: syz-executor.2 Not tainted 4.14.205-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 do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1016 do_softirq+0xee/0x160 kernel/softirq.c:332 __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 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x953/0x2c40 kernel/exit.c:865 do_group_exit+0xf8/0x2c0 kernel/exit.c:962 get_signal+0x2f6/0x1ab0 kernel/signal.c:2423 do_signal+0x7f/0x18b0 arch/x86/kernel/signal.c:814 exit_to_usermode_loop+0x11e/0x190 arch/x86/entry/common.c:160 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: 0033:0x45de59 RSP: 002b:00007ffeda2815e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: 0000000000000000 RBX: 000000000000002d RCX: 000000000045de59 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000118bf2c RBP: 000000000118bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 00007ffeda2816c0 R11: 0000000000000246 R12: 0000000000057f38 R13: 0000000000057f0b R14: 00000000000003e8 R15: 000000000118bf2c Allocated by task 8600: 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 8594: 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 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x953/0x2c40 kernel/exit.c:865 do_group_exit+0xf8/0x2c0 kernel/exit.c:962 get_signal+0x2f6/0x1ab0 kernel/signal.c:2423 do_signal+0x7f/0x18b0 arch/x86/kernel/signal.c:814 exit_to_usermode_loop+0x11e/0x190 arch/x86/entry/common.c:160 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 ffff8880a0885680 which belongs to the cache kmalloc-1024 of size 1024 The buggy address is located 208 bytes inside of 1024-byte region [ffff8880a0885680, ffff8880a0885a80) The buggy address belongs to the page: page:ffffea0002822100 count:1 mapcount:0 mapping:ffff8880a0884000 index:0xffff8880a0885b00 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff8880a0884000 ffff8880a0885b00 0000000100000005 raw: ffffea00029100a0 ffffea0002629020 ffff8880b6400ac0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a0885600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8880a0885680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8880a0885700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880a0885780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a0885800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================