bisecting fixing commit since fa5941f45d7ed070118b7c209b7f2c3a034293bd building syzkaller on b617407b25b37a7a8efa47127005d1f20dd0abe1 testing commit fa5941f45d7ed070118b7c209b7f2c3a034293bd with gcc (GCC) 8.1.0 kernel signature: ee7b6f5b901e9e30e4ae91e75cdd043269374d890b28b3c7f406b3113821e533 all runs: crashed: INFO: task hung in vivid_stop_generating_vid_cap testing current HEAD 9fa690a2a016e1b55356835f047b952e67d3d73a testing commit 9fa690a2a016e1b55356835f047b952e67d3d73a with gcc (GCC) 8.1.0 kernel signature: a9df5a04f3dbdc1cdd1df6319f81bb1f9d8aaf8b20291ea5bb8664e4ac18954e all runs: crashed: KASAN: use-after-free Read in __vb2_perform_fileio revisions tested: 2, total time: 28m2.422489363s (build: 16m52.255846577s, test: 10m24.258386792s) the crash still happens on HEAD commit msg: Linux 4.14.169 crash: KASAN: use-after-free Read in __vb2_perform_fileio IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_1: link becomes ready IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready 8021q: adding VLAN 0 to HW filter on device batadv0 vivid-000: kernel_thread() failed ================================================================== 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 ffff88809f71be5c by task syz-executor.2/7183 CPU: 1 PID: 7183 Comm: syz-executor.2 Not tainted 4.14.169-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+0x135/0x240 drivers/media/v4l2-core/v4l2-dev.c:309 __vfs_read+0xde/0x840 fs/read_write.c:411 vfs_read+0xf5/0x300 fs/read_write.c:447 SYSC_read fs/read_write.c:574 [inline] SyS_read+0x100/0x250 fs/read_write.c:567 do_syscall_64+0x1c9/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x458da9 RSP: 002b:00007fd61ca2ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458da9 RDX: 0000000000000052 RSI: 0000000020000540 RDI: 0000000000000003 RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fd61ca2f6d4 R13: 00000000004c4ac8 R14: 00000000004da088 R15: 00000000ffffffff Allocated by task 7174: 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+0x152/0x7b0 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+0x135/0x240 drivers/media/v4l2-core/v4l2-dev.c:309 __vfs_read+0xde/0x840 fs/read_write.c:411 vfs_read+0xf5/0x300 fs/read_write.c:447 SYSC_read fs/read_write.c:574 [inline] SyS_read+0x100/0x250 fs/read_write.c:567 do_syscall_64+0x1c9/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 Freed by task 7164: 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+0xee/0x1a0 drivers/media/v4l2-core/v4l2-dev.c:446 __fput+0x235/0x750 fs/file_table.c:210 ____fput+0x9/0x10 fs/file_table.c:244 task_work_run+0xeb/0x180 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+0x418/0x5b0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x42/0xb7 The buggy address belongs to the object at ffff88809f71bb40 which belongs to the cache kmalloc-1024 of size 1024 The buggy address is located 796 bytes inside of 1024-byte region [ffff88809f71bb40, ffff88809f71bf40) The buggy address belongs to the page: page:ffffea00027dc680 count:1 mapcount:0 mapping:ffff88809f71a040 index:0x0 compound_mapcount: 0 flags: 0x1fffc0000008100(slab|head) raw: 01fffc0000008100 ffff88809f71a040 0000000000000000 0000000100000007 raw: ffffea00029a4520 ffffea000264e3a0 ffff8880aa800ac0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88809f71bd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809f71bd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88809f71be00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88809f71be80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809f71bf00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc 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