bisecting fixing commit since 59456c9cc40c8f75b5a7efa0fe1f211d9c6fcaf1 building syzkaller on 2489ab887a86e8b1b253aef742e365a606db3a4f testing commit 59456c9cc40c8f75b5a7efa0fe1f211d9c6fcaf1 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 82812192a9d7ce3b10bb7ca76b12f951d793160c18fccfd27c2374462179bdd9 run #0: crashed: KASAN: use-after-free Read in skb_dequeue run #1: crashed: KASAN: use-after-free Read in h4_recv_buf run #2: crashed: KASAN: use-after-free Read in skb_dequeue run #3: crashed: KASAN: use-after-free Read in skb_dequeue run #4: crashed: KASAN: use-after-free Read in skb_dequeue run #5: crashed: KASAN: use-after-free Read in skb_dequeue run #6: crashed: KASAN: use-after-free Read in skb_dequeue run #7: crashed: KASAN: use-after-free Read in skb_dequeue run #8: crashed: KASAN: use-after-free Read in skb_dequeue run #9: crashed: KASAN: use-after-free Read in skb_dequeue run #10: crashed: KASAN: use-after-free Read in skb_dequeue run #11: crashed: KASAN: use-after-free Read in h4_recv_buf run #12: crashed: KASAN: use-after-free Read in skb_dequeue run #13: crashed: KASAN: use-after-free Read in skb_dequeue run #14: crashed: KASAN: use-after-free Read in skb_dequeue run #15: crashed: KASAN: use-after-free Write in hci_recv_frame run #16: crashed: KASAN: use-after-free Read in skb_dequeue run #17: crashed: KASAN: use-after-free Read in skb_dequeue run #18: crashed: KASAN: use-after-free Write in hci_recv_frame run #19: crashed: KASAN: use-after-free Read in skb_dequeue testing current HEAD b172b44fcb1771e083aad806fa96f3f60e2ddfac testing commit b172b44fcb1771e083aad806fa96f3f60e2ddfac compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 6cb549b63ef7dcc2ca93ba82e5b87e3830ef10fbe5779bb6a0e9b2255856c30e run #0: crashed: KASAN: use-after-free Read in skb_dequeue run #1: crashed: KASAN: use-after-free Read in skb_dequeue run #2: crashed: KASAN: use-after-free Read in skb_dequeue run #3: crashed: KASAN: use-after-free Read in skb_dequeue run #4: crashed: KASAN: use-after-free Read in skb_dequeue run #5: crashed: KASAN: use-after-free Read in h4_recv_buf run #6: crashed: KASAN: use-after-free Write in hci_recv_frame run #7: crashed: KASAN: use-after-free Read in skb_dequeue run #8: crashed: KASAN: use-after-free Read in skb_dequeue run #9: crashed: KASAN: use-after-free Read in skb_dequeue revisions tested: 2, total time: 32m55.757193369s (build: 18m34.076165977s, test: 13m54.767926863s) the crash still happens on HEAD commit msg: Linux 4.19.206 crash: KASAN: use-after-free Read in skb_dequeue Bluetooth: hci11: command 0x1009 tx timeout Bluetooth: hci8: command 0x1009 tx timeout Bluetooth: hci6: Received unexpected HCI Event 00000000 Bluetooth: hci6: Frame reassembly failed (-84) ================================================================== BUG: KASAN: use-after-free in __skb_unlink include/linux/skbuff.h:1916 [inline] BUG: KASAN: use-after-free in __skb_dequeue include/linux/skbuff.h:1936 [inline] BUG: KASAN: use-after-free in skb_dequeue+0x1e7/0x1f0 net/core/skbuff.c:2838 Read of size 8 at addr ffff8880a2028cc0 by task kworker/u5:4/8478 Bluetooth: hci8: Frame reassembly failed (-84) CPU: 0 PID: 8478 Comm: kworker/u5:4 Not tainted 4.19.206-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: hci6 hci_rx_work Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x17c/0x226 lib/dump_stack.c:118 print_address_description.cold.6+0x9/0x211 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report mm/kasan/report.c:412 [inline] kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:396 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 __skb_unlink include/linux/skbuff.h:1916 [inline] __skb_dequeue include/linux/skbuff.h:1936 [inline] skb_dequeue+0x1e7/0x1f0 net/core/skbuff.c:2838 hci_rx_work+0x54/0xa70 net/bluetooth/hci_core.c:4331 process_one_work+0x7b9/0x15a0 kernel/workqueue.c:2153 worker_thread+0x85/0xb60 kernel/workqueue.c:2296 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Allocated by task 10824: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:553 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:538 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490 kmem_cache_alloc_node+0x14f/0x3e0 mm/slab.c:3649 Bluetooth: hci8: Received unexpected HCI Event 00000000 __alloc_skb+0xa7/0x580 net/core/skbuff.c:193 Bluetooth: hci9: Frame reassembly failed (-84) alloc_skb include/linux/skbuff.h:995 [inline] bt_skb_alloc include/net/bluetooth/bluetooth.h:339 [inline] h4_recv_buf+0x429/0xba0 drivers/bluetooth/hci_h4.c:197 h4_recv+0xc8/0x1d0 drivers/bluetooth/hci_h4.c:131 hci_uart_tty_receive+0x1ce/0x460 drivers/bluetooth/hci_ldisc.c:621 tiocsti drivers/tty/tty_io.c:2194 [inline] tty_ioctl+0x647/0x1290 drivers/tty/tty_io.c:2580 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 Bluetooth: hci9: Received unexpected HCI Event 00000000 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 8478: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x13c/0x220 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3503 [inline] kmem_cache_free+0x83/0x290 mm/slab.c:3765 kfree_skbmem+0x89/0xf0 net/core/skbuff.c:595 __kfree_skb net/core/skbuff.c:655 [inline] kfree_skb+0xa1/0x280 net/core/skbuff.c:672 hci_event_packet+0x304/0x68e0 net/bluetooth/hci_event.c:5963 hci_rx_work+0x385/0xa70 net/bluetooth/hci_core.c:4366 process_one_work+0x7b9/0x15a0 kernel/workqueue.c:2153 Bluetooth: hci10: Frame reassembly failed (-84) worker_thread+0x85/0xb60 kernel/workqueue.c:2296 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 The buggy address belongs to the object at ffff8880a2028cc0 which belongs to the cache skbuff_head_cache of size 232 The buggy address is located 0 bytes inside of 232-byte region [ffff8880a2028cc0, ffff8880a2028da8) The buggy address belongs to the page: page:ffffea0002880a00 count:1 mapcount:0 mapping:ffff88823b331240 index:0x0 Bluetooth: hci11: Frame reassembly failed (-84) flags: 0xfff00000000100(slab) raw: 00fff00000000100 ffffea0002884188 ffffea0002538a88 ffff88823b331240 raw: 0000000000000000 ffff8880a2028040 000000010000000c 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a2028b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a2028c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc >ffff8880a2028c80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ^ ffff8880a2028d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a2028d80: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc ==================================================================