bisecting fixing commit since c6db52a88798e5a0dfef80041ad4d33cc8cf04eb building syzkaller on 2420d1bcbcd9f5d5893c1aab8096cce81721dac2 testing commit c6db52a88798e5a0dfef80041ad4d33cc8cf04eb with gcc (GCC) 8.1.0 kernel signature: f35ee71a33019c13d136e7a13ab2bd75a430ea05df0b3dfdea954d1d3278a58d 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: WARNING: ODEBUG bug in enqueue_hrtimer run #3: crashed: KASAN: use-after-free Read in hrtimer_debug_hint 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 tasklet_action run #7: crashed: KASAN: use-after-free Read in tasklet_action 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 2b79150141611d3c6e1b55d4e70f49602482f0b8 testing commit 2b79150141611d3c6e1b55d4e70f49602482f0b8 with gcc (GCC) 8.1.0 kernel signature: 70f37fb0be4bc22c1312936cb333d99b12a6f89d1768250cb1c0634bd440bb50 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 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: WARNING: ODEBUG bug in bcm_remove_op run #6: crashed: KASAN: use-after-free Read in bcm_can_tx run #7: crashed: KASAN: use-after-free Read in bcm_can_tx run #8: OK run #9: OK revisions tested: 2, total time: 35m6.434966649s (build: 15m58.913985627s, test: 18m27.995634297s) the crash still happens on HEAD commit msg: Linux 4.14.203 crash: KASAN: use-after-free Read in bcm_can_tx ================================================================== BUG: KASAN: use-after-free in bcm_can_tx+0x538/0x640 net/can/bcm.c:304 Read of size 4 at addr ffff8880a5297384 by task syz-executor.4/5821 CPU: 1 PID: 5821 Comm: syz-executor.4 Not tainted 4.14.203-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+0x538/0x640 net/can/bcm.c:304 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:touch_buffer fs/buffer.c:66 [inline] RIP: 0010:__find_get_block+0x229/0xbd0 fs/buffer.c:1361 RSP: 0018:ffff8880878c79f8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10 RAX: dffffc0000000000 RBX: ffff88808b69e9d8 RCX: ffffed1014228998 RDX: 1ffff110116d3d3d RSI: 0000000000000000 RDI: ffff88808b69e9e8 RBP: ffff8880878c7a50 R08: 1ffff11014228998 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 000000000000041e R14: ffff88823999e700 R15: ffffffff87f15e18 sb_find_get_block include/linux/buffer_head.h:346 [inline] recently_deleted fs/ext4/ialloc.c:693 [inline] find_inode_bit.isra.1+0x1c8/0x4c0 fs/ext4/ialloc.c:733 __ext4_new_inode+0xb93/0x47f0 fs/ext4/ialloc.c:925 ext4_symlink+0x2a8/0xb90 fs/ext4/namei.c:3175 vfs_symlink+0x2f8/0x520 fs/namei.c:4156 SYSC_symlinkat fs/namei.c:4183 [inline] SyS_symlinkat+0x17e/0x1c0 fs/namei.c:4163 SYSC_symlink fs/namei.c:4196 [inline] SyS_symlink+0x11/0x20 fs/namei.c:4194 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x45c877 RSP: 002b:00007ffcd8fbc908 EFLAGS: 00000202 ORIG_RAX: 0000000000000058 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000045c877 RDX: 00007ffcd8fbc9a3 RSI: 00000000004c2645 RDI: 00007ffcd8fbc990 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000013 R10: 0000000000000075 R11: 0000000000000202 R12: 0000000000000001 R13: 00007ffcd8fbc940 R14: 0000000000000000 R15: 00007ffcd8fbc950 Allocated by task 5817: 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 5807: 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 ffff8880a5297240 which belongs to the cache kmalloc-1024 of size 1024 The buggy address is located 324 bytes inside of 1024-byte region [ffff8880a5297240, ffff8880a5297640) The buggy address belongs to the page: page:ffffea000294a580 count:1 mapcount:0 mapping:ffff8880a5296040 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff8880a5296040 0000000000000000 0000000100000007 raw: ffffea0002c209a0 ffffea0002990ba0 ffff8880b6400ac0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a5297280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a5297300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8880a5297380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880a5297400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a5297480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================