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BUG: KASAN: slab-out-of-bounds in decode_data.part.0+0x235/0x260 drivers/net/hamradio/6pack.c:843
Write of size 1 at addr ffff8880925c944e by task kworker/u4:3/228

CPU: 1 PID: 228 Comm: kworker/u4:3 Not tainted 5.6.0-rc3-next-20200228-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+0x188/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:374
 __kasan_report.cold+0x1a/0x32 mm/kasan/report.c:506
 kasan_report+0xe/0x20 mm/kasan/common.c:618
 decode_data.part.0+0x235/0x260 drivers/net/hamradio/6pack.c:843
 decode_data drivers/net/hamradio/6pack.c:965 [inline]
 sixpack_decode drivers/net/hamradio/6pack.c:968 [inline]
 sixpack_receive_buf drivers/net/hamradio/6pack.c:458 [inline]
 sixpack_receive_buf+0xc24/0x1210 drivers/net/hamradio/6pack.c:435
 tty_ldisc_receive_buf+0x14a/0x190 drivers/tty/tty_buffer.c:465
 tty_port_default_receive_buf+0x78/0xa0 drivers/tty/tty_port.c:38
 receive_buf drivers/tty/tty_buffer.c:481 [inline]
 flush_to_ldisc+0x21d/0x390 drivers/tty/tty_buffer.c:533
 process_one_work+0x94b/0x1690 kernel/workqueue.c:2266
 worker_thread+0x96/0xe20 kernel/workqueue.c:2412
 kthread+0x357/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 9469:
 save_stack+0x1b/0x40 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 __kasan_kmalloc mm/kasan/common.c:492 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:465
 kmalloc_node include/linux/slab.h:578 [inline]
 kvmalloc_node+0x61/0xf0 mm/util.c:574
 kvmalloc include/linux/mm.h:650 [inline]
 kvzalloc include/linux/mm.h:658 [inline]
 alloc_netdev_mqs+0x97/0xde0 net/core/dev.c:9786
 sixpack_open+0xfa/0xa41 drivers/net/hamradio/6pack.c:563
 tty_ldisc_open.isra.0+0x9b/0x110 drivers/tty/tty_ldisc.c:464
 tty_set_ldisc+0x2e8/0x670 drivers/tty/tty_ldisc.c:591
 tiocsetd drivers/tty/tty_io.c:2337 [inline]
 tty_ioctl+0xcdf/0x1440 drivers/tty/tty_io.c:2597
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x11a/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770
 do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8880925c8000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1102 bytes to the right of
 4096-byte region [ffff8880925c8000, ffff8880925c9000)
The buggy address belongs to the page:
page:ffffea0002497200 refcount:1 mapcount:0 mapping:0000000039784f6d index:0x0 head:ffffea0002497200 order:1 compound_mapcount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea00024f8388 ffffea0002899788 ffff8880aa002000
raw: 0000000000000000 ffff8880925c8000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880925c9300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880925c9380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880925c9400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                              ^
 ffff8880925c9480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880925c9500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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