bisecting fixing commit since 98db2bf27b9ed2d5ed0b6c9c8a4bfcb127a19796
building syzkaller on 2ffa6679c4790a83f26a1b674ed34800e028fe2e
testing commit 98db2bf27b9ed2d5ed0b6c9c8a4bfcb127a19796 with gcc (GCC) 8.1.0
kernel signature: 58c802216fe192a4c74df83da9590c8abc45c7ba0c7ea693f44880882431cc4e
all runs: crashed: KASAN: slab-out-of-bounds Write in decode_data
testing current HEAD a41ba30d9df20fe141c92aacbb56b6b077f19716
testing commit a41ba30d9df20fe141c92aacbb56b6b077f19716 with gcc (GCC) 8.1.0
kernel signature: 784eee06945bf698c2f7f4f576e88878656bf2687bfbf138156e109c8a89ec70
all runs: crashed: KASAN: slab-out-of-bounds Write in decode_data
revisions tested: 2, total time: 23m16.486465868s (build: 16m37.216479211s, test: 6m6.377988125s)
the crash still happens on HEAD
commit msg: Linux 4.14.181
crash: KASAN: slab-out-of-bounds Write in decode_data
IPv6: ADDRCONF(NETDEV_UP): macvtap0: link is not ready
sp0: Synchronizing with TNC
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1
==================================================================
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
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 ffff8880a51e3a4e by task kworker/u4:1/22

CPU: 1 PID: 22 Comm: kworker/u4:1 Not tainted 4.14.181-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:3e) already exists on: batadv_slave_1
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+0x722/0x1180 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
 kthread+0x338/0x400 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 7765:
 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
 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:8100
 sixpack_open+0xda/0xc7e drivers/net/hamradio/6pack.c:572
 tty_ldisc_open.isra.1+0x61/0xa0 drivers/tty/tty_ldisc.c:481
 tty_set_ldisc+0x249/0x5a0 drivers/tty/tty_ldisc.c:606
 tiocsetd drivers/tty/tty_io.c:2351 [inline]
 tty_ioctl+0x300/0x1260 drivers/tty/tty_io.c:2595
 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
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8880a51e26c0
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 910 bytes to the right of
 4096-byte region [ffff8880a51e26c0, ffff8880a51e36c0)
The buggy address belongs to the page:
page:ffffea0002947880 count:1 mapcount:0 mapping:ffff8880a51e26c0 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff8880a51e26c0 0000000000000000 0000000100000001
raw: ffffea00029444a0 ffffea000294b120 ffff8880aa800dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a51e3900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a51e3980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a51e3a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                              ^
 ffff8880a51e3a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a51e3b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================