bisecting fixing commit since 3ffe1e79c174b2093f7ee3df589a7705572c9620 building syzkaller on faeffb0030134849d132c0040f330500e9056b24 testing commit 3ffe1e79c174b2093f7ee3df589a7705572c9620 with gcc (GCC) 8.1.0 kernel signature: d830a558843ca7520258af9948f2397045f741d35edef20795b4f20e9e542ccc run #0: crashed: WARNING in __vb2_queue_cancel run #1: crashed: WARNING in __vb2_queue_cancel run #2: crashed: WARNING in __vb2_queue_cancel run #3: crashed: WARNING in __vb2_queue_cancel run #4: crashed: INFO: task hung in vivid_stop_generating_vid_cap run #5: crashed: INFO: task hung in vivid_stop_generating_vid_cap run #6: crashed: INFO: task hung in vivid_stop_generating_vid_cap run #7: crashed: INFO: task hung in vivid_stop_generating_vid_cap run #8: crashed: INFO: task hung in vivid_stop_generating_vid_cap run #9: crashed: INFO: task hung in vivid_stop_generating_vid_cap testing current HEAD e0f8b8a65a473a8baa439cf865a694bbeb83fe90 testing commit e0f8b8a65a473a8baa439cf865a694bbeb83fe90 with gcc (GCC) 8.1.0 kernel signature: c28ce72367176e7a644c5794c4fb929fa45df308c7e9bbd9d5b0da92e87dbe3e all runs: crashed: KASAN: use-after-free Read in __vb2_perform_fileio revisions tested: 2, total time: 27m38.358080255s (build: 16m32.791843943s, test: 10m15.051275881s) the crash still happens on HEAD commit msg: Linux 4.14.170 crash: KASAN: use-after-free Read in __vb2_perform_fileio 8021q: adding VLAN 0 to HW filter on device batadv0 8021q: adding VLAN 0 to HW filter on device batadv0 IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready 8021q: adding VLAN 0 to HW filter on device batadv0 ================================================================== BUG: KASAN: use-after-free in __vb2_perform_fileio+0x10fd/0x12b0 drivers/media/v4l2-core/videobuf2-core.c:2379 Read of size 4 at addr ffff888086fb435c by task syz-executor.1/7119 CPU: 0 PID: 7119 Comm: syz-executor.1 Not tainted 4.14.170-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+0xf7/0x13b lib/dump_stack.c:58 print_address_description.cold.7+0x9/0x1c9 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report.cold.8+0x11a/0x2d3 mm/kasan/report.c:409 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429 __vb2_perform_fileio+0x10fd/0x12b0 drivers/media/v4l2-core/videobuf2-core.c:2379 vb2_read+0xf/0x20 drivers/media/v4l2-core/videobuf2-core.c:2490 vb2_fop_read+0x1b6/0x390 drivers/media/v4l2-core/videobuf2-v4l2.c:895 v4l2_read+0x133/0x240 drivers/media/v4l2-core/v4l2-dev.c:309 do_loop_readv_writev fs/read_write.c:695 [inline] do_iter_read+0x35e/0x570 fs/read_write.c:919 vfs_readv+0xb6/0x110 fs/read_write.c:981 do_readv+0x10d/0x320 fs/read_write.c:1014 SYSC_readv fs/read_write.c:1101 [inline] SyS_readv+0xb/0x10 fs/read_write.c:1098 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x459829 RSP: 002b:00007f23dd964c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000013 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829 RDX: 0000000000000001 RSI: 0000000020000180 RDI: 0000000000000003 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f23dd9656d4 R13: 00000000004c6b54 R14: 00000000004dc048 R15: 00000000ffffffff Allocated by task 7119: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:551 kmem_cache_alloc_trace+0x152/0x7a0 mm/slab.c:3618 kmalloc include/linux/slab.h:488 [inline] kzalloc include/linux/slab.h:661 [inline] __vb2_init_fileio+0x160/0xaf0 drivers/media/v4l2-core/videobuf2-core.c:2224 __vb2_perform_fileio+0xa9f/0x12b0 drivers/media/v4l2-core/videobuf2-core.c:2358 vb2_read+0xf/0x20 drivers/media/v4l2-core/videobuf2-core.c:2490 vb2_fop_read+0x1b6/0x390 drivers/media/v4l2-core/videobuf2-v4l2.c:895 v4l2_read+0x133/0x240 drivers/media/v4l2-core/v4l2-dev.c:309 do_loop_readv_writev fs/read_write.c:695 [inline] do_iter_read+0x35e/0x570 fs/read_write.c:919 vfs_readv+0xb6/0x110 fs/read_write.c:981 do_readv+0x10d/0x320 fs/read_write.c:1014 SYSC_readv fs/read_write.c:1101 [inline] SyS_readv+0xb/0x10 fs/read_write.c:1098 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 Freed by task 7121: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3496 [inline] kfree+0xcc/0x270 mm/slab.c:3815 __vb2_cleanup_fileio+0xee/0x140 drivers/media/v4l2-core/videobuf2-core.c:2317 vb2_core_queue_release+0xf/0x70 drivers/media/v4l2-core/videobuf2-core.c:2040 vb2_queue_release drivers/media/v4l2-core/videobuf2-v4l2.c:669 [inline] _vb2_fop_release+0x1ac/0x280 drivers/media/v4l2-core/videobuf2-v4l2.c:840 vb2_fop_release+0x66/0xd0 drivers/media/v4l2-core/videobuf2-v4l2.c:854 vivid_fop_release+0x15f/0x3a0 drivers/media/platform/vivid/vivid-core.c:486 v4l2_release+0xeb/0x1a0 drivers/media/v4l2-core/v4l2-dev.c:446 __fput+0x232/0x750 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+0x16a/0x1b0 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+0x42/0xb7 The buggy address belongs to the object at ffff888086fb4040 which belongs to the cache kmalloc-1024 of size 1024 The buggy address is located 796 bytes inside of 1024-byte region [ffff888086fb4040, ffff888086fb4440) The buggy address belongs to the page: page:ffffea00021bed00 count:1 mapcount:0 mapping:ffff888086fb4040 index:0x0 compound_mapcount: 0 flags: 0x1fffc0000008100(slab|head) raw: 01fffc0000008100 ffff888086fb4040 0000000000000000 0000000100000007 raw: ffffea000268dca0 ffffea00021e9920 ffff8880aa800ac0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888086fb4200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888086fb4280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888086fb4300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888086fb4380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888086fb4400: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ==================================================================