bisecting fixing commit since 4fccc2503536a564a4ba31a1d50439854201659f
building syzkaller on 2c36e7a75f8689b3da20e1a81a2ee5391f3af6e5
testing commit 4fccc2503536a564a4ba31a1d50439854201659f with gcc (GCC) 8.1.0
kernel signature: d7f0406bca4bf735843a8c1579046fdfce2f1170d4141fcee046caee91241c95
all runs: crashed: KASAN: slab-out-of-bounds Write in decode_data
testing current HEAD ad326970d25cc85128cd22d62398751ad072efff
testing commit ad326970d25cc85128cd22d62398751ad072efff with gcc (GCC) 8.1.0
kernel signature: 52ed1200d2a598b8c26f0ac5bae0b3e79763667184f3af72d769dec5f1eee865
all runs: crashed: KASAN: slab-out-of-bounds Write in decode_data
revisions tested: 2, total time: 25m43.020935429s (build: 18m43.283089447s, test: 6m3.159943823s)
the crash still happens on HEAD
commit msg: Linux 4.19.152
crash: KASAN: slab-out-of-bounds Write in decode_data
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_batadv: link becomes ready
sp0: Synchronizing with TNC
==================================================================
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready
BUG: KASAN: slab-out-of-bounds in decode_data.part.2+0x23c/0x280 drivers/net/hamradio/6pack.c:863
Write of size 1 at addr ffff88808cdc990e by task kworker/u4:4/943

CPU: 0 PID: 943 Comm: kworker/u4:4 Not tainted 4.19.152-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x123/0x177 lib/dump_stack.c:118
 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
 __asan_report_store1_noabort+0x17/0x20 mm/kasan/report.c:435
 decode_data.part.2+0x23c/0x280 drivers/net/hamradio/6pack.c:863
 decode_data drivers/net/hamradio/6pack.c:985 [inline]
 sixpack_decode drivers/net/hamradio/6pack.c:988 [inline]
 sixpack_receive_buf+0x722/0x1120 drivers/net/hamradio/6pack.c:458
 tty_ldisc_receive_buf+0xff/0x1b0 drivers/tty/tty_buffer.c:460
 tty_port_default_receive_buf+0x5f/0x90 drivers/tty/tty_port.c:38
 receive_buf drivers/tty/tty_buffer.c:476 [inline]
 flush_to_ldisc+0x1aa/0x3a0 drivers/tty/tty_buffer.c:528
 process_one_work+0x830/0x1670 kernel/workqueue.c:2155
 worker_thread+0x85/0xb60 kernel/workqueue.c:2298
 kthread+0x347/0x410 kernel/kthread.c:259
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 7821:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
 __do_kmalloc_node mm/slab.c:3689 [inline]
 __kmalloc_node+0x50/0x70 mm/slab.c:3696
 kmalloc_node include/linux/slab.h:557 [inline]
 kvmalloc_node+0x68/0x70 mm/util.c:423
 kvmalloc include/linux/mm.h:577 [inline]
 kvzalloc include/linux/mm.h:585 [inline]
 alloc_netdev_mqs+0x5d/0xc80 net/core/dev.c:9139
 sixpack_open+0xe7/0xbc2 drivers/net/hamradio/6pack.c:563
 tty_ldisc_open.isra.3+0x65/0xa0 drivers/tty/tty_ldisc.c:469
 tty_set_ldisc+0x249/0x5a0 drivers/tty/tty_ldisc.c:594
 tiocsetd drivers/tty/tty_io.c:2359 [inline]
 tty_ioctl+0x31e/0x1290 drivers/tty/tty_io.c:2603
 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
 __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
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff88808cdc8580
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 910 bytes to the right of
 4096-byte region [ffff88808cdc8580, ffff88808cdc9580)
The buggy address belongs to the page:
page:ffffea0002337200 count:1 mapcount:0 mapping:ffff88812c29cdc0 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea00023e2688 ffffea0002325b08 ffff88812c29cdc0
raw: 0000000000000000 ffff88808cdc8580 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808cdc9800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88808cdc9880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88808cdc9900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                      ^
 ffff88808cdc9980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88808cdc9a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1