bisecting fixing commit since 98db2bf27b9ed2d5ed0b6c9c8a4bfcb127a19796 building syzkaller on 2ffa6679c4790a83f26a1b674ed34800e028fe2e testing commit 98db2bf27b9ed2d5ed0b6c9c8a4bfcb127a19796 with gcc (GCC) 8.1.0 kernel signature: 2b8da29cb070680ea7e9cbfcf51510c48b36a4d9eea1316831b9d4f94f18a2b2 run #0: crashed: KASAN: slab-out-of-bounds Write in decode_data run #1: crashed: KASAN: slab-out-of-bounds Write in decode_data run #2: crashed: KASAN: slab-out-of-bounds Write in decode_data run #3: crashed: KASAN: use-after-free Write in decode_data run #4: crashed: KASAN: slab-out-of-bounds Write in decode_data run #5: crashed: KASAN: slab-out-of-bounds Write in decode_data run #6: crashed: KASAN: slab-out-of-bounds Write in decode_data run #7: crashed: KASAN: slab-out-of-bounds Write in decode_data run #8: crashed: KASAN: slab-out-of-bounds Write in decode_data run #9: crashed: KASAN: slab-out-of-bounds Write in decode_data testing current HEAD 01364dad1d4577e27a57729d41053f661bb8a5b9 testing commit 01364dad1d4577e27a57729d41053f661bb8a5b9 with gcc (GCC) 8.1.0 kernel signature: 46ef990ab0bcbf6d1eb7aa5c0d251673bbf06d1d1e74e236a7bdb8e83020c5c9 all runs: crashed: KASAN: slab-out-of-bounds Write in decode_data revisions tested: 2, total time: 25m43.469372005s (build: 17m18.661811054s, test: 6m47.839606599s) the crash still happens on HEAD commit msg: Linux 4.14.174 crash: KASAN: slab-out-of-bounds Write in decode_data IPv6: ADDRCONF(NETDEV_UP): veth1_to_batadv: link is not ready ================================================================== batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 BUG: KASAN: slab-out-of-bounds in decode_data.part.2+0x23c/0x280 drivers/net/hamradio/6pack.c:874 Write of size 1 at addr ffff8880a53ed84e by task kworker/u4:4/2459 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! CPU: 1 PID: 2459 Comm: kworker/u4:4 Not tainted 4.14.174-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events_unbound flush_to_ldisc batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 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_store1_noabort+0x17/0x20 mm/kasan/report.c:432 decode_data.part.2+0x23c/0x280 drivers/net/hamradio/6pack.c:874 decode_data drivers/net/hamradio/6pack.c:1004 [inline] sixpack_decode drivers/net/hamradio/6pack.c:1007 [inline] sixpack_receive_buf+0x721/0x1180 drivers/net/hamradio/6pack.c:458 tty_ldisc_receive_buf+0xff/0x1b0 drivers/tty/tty_buffer.c:459 tty_port_default_receive_buf+0x5f/0x90 drivers/tty/tty_port.c:37 receive_buf drivers/tty/tty_buffer.c:475 [inline] flush_to_ldisc+0x197/0x390 drivers/tty/tty_buffer.c:527 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2116 worker_thread+0xcc/0xee0 kernel/workqueue.c:2250 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! kthread+0x338/0x400 kernel/kthread.c:232 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 IPv6: ADDRCONF(NETDEV_UP): batadv_slave_0: link is not ready Allocated by task 7286: 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 __do_kmalloc_node mm/slab.c:3682 [inline] __kmalloc_node+0x50/0x70 mm/slab.c:3689 batman_adv: batadv0: Interface activated: batadv_slave_0 kmalloc_node include/linux/slab.h:530 [inline] kvmalloc_node+0x70/0x80 mm/util.c:397 kvmalloc include/linux/mm.h:531 [inline] kvzalloc include/linux/mm.h:539 [inline] alloc_netdev_mqs+0x60/0xb40 net/core/dev.c:8097 sixpack_open+0xda/0xc7e drivers/net/hamradio/6pack.c:572 tty_ldisc_open.isra.1+0x60/0xa0 drivers/tty/tty_ldisc.c:481 tty_set_ldisc+0x249/0x5a0 drivers/tty/tty_ldisc.c:606 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 tiocsetd drivers/tty/tty_io.c:2351 [inline] tty_ioctl+0x300/0x1260 drivers/tty/tty_io.c:2595 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x74/0x80 fs/ioctl.c:692 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 entry_SYSCALL_64_after_hwframe+0x42/0xb7 Freed by task 0: (stack is not available) The buggy address belongs to the object at ffff8880a53ec4c0 which belongs to the cache kmalloc-4096 of size 4096 The buggy address is located 910 bytes to the right of 4096-byte region [ffff8880a53ec4c0, ffff8880a53ed4c0) The buggy address belongs to the page: batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! page:ffffea000294fb00 count:1 mapcount:0 mapping:ffff8880a53ec4c0 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff8880a53ec4c0 0000000000000000 0000000100000001 raw: ffffea000294fba0 ffffea0002954220 ffff8880aa800dc0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a53ed700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8880a53ed780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff8880a53ed800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff8880a53ed880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8880a53ed900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================