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SubjectKASAN: slab-out-of-bounds Read in j1939_tp_txtimer

syzbot found the following crash on:

HEAD commit: 4a94c433 Merge tag 'tpmdd-next-20191219' of git://git.infr..
git tree: upstream
console output:
kernel config:
dashboard link:
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:
C reproducer:

The bug was bisected to:

commit 9d71dd0c70099914fcd063135da3c580865e924c
Author: The j1939 authors <>
Date: Mon Oct 8 09:48:36 2018 +0000

can: add support of SAE J1939 protocol

bisection log:
final crash:
console output:

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")

vcan0: j1939_xtp_rx_abort_one: 0x000000000820f4a9: 0x00000: (3) A timeout
occurred and this is the connection abort to close the session.
vcan0: j1939_xtp_rx_abort_one: 0x00000000b1f6d063: 0x00000: (3) A timeout
occurred and this is the connection abort to close the session.
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:380 [inline]
BUG: KASAN: slab-out-of-bounds in j1939_session_tx_dat
net/can/j1939/transport.c:790 [inline]
BUG: KASAN: slab-out-of-bounds in j1939_xtp_txnext_transmiter
net/can/j1939/transport.c:847 [inline]
BUG: KASAN: slab-out-of-bounds in j1939_tp_txtimer+0x777/0x1b00
Read of size 7 at addr ffff8880905826af by task ksoftirqd/1/16

CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 5.5.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x197/0x210 lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
__kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
kasan_report+0x12/0x20 mm/kasan/common.c:639
check_memory_region_inline mm/kasan/generic.c:185 [inline]
check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
memcpy+0x24/0x50 mm/kasan/common.c:125
memcpy include/linux/string.h:380 [inline]
j1939_session_tx_dat net/can/j1939/transport.c:790 [inline]
j1939_xtp_txnext_transmiter net/can/j1939/transport.c:847 [inline]
j1939_tp_txtimer+0x777/0x1b00 net/can/j1939/transport.c:1095
__run_hrtimer kernel/time/hrtimer.c:1517 [inline]
__hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1579
hrtimer_run_softirq+0x17e/0x270 kernel/time/hrtimer.c:1596
__do_softirq+0x262/0x98c kernel/softirq.c:292
run_ksoftirqd kernel/softirq.c:603 [inline]
run_ksoftirqd+0x8e/0x110 kernel/softirq.c:595
smpboot_thread_fn+0x6a3/0xa40 kernel/smpboot.c:165
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 9315:
save_stack+0x23/0x90 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:513 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:486
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:527
__do_kmalloc mm/slab.c:3656 [inline]
__kmalloc+0x163/0x770 mm/slab.c:3665
kmalloc include/linux/slab.h:561 [inline]
kzalloc include/linux/slab.h:670 [inline]
__register_sysctl_table+0xc7/0xef0 fs/proc/proc_sysctl.c:1331
register_net_sysctl+0x29/0x30 net/sysctl_net.c:121
__addrconf_sysctl_register+0x221/0x430 net/ipv6/addrconf.c:6850
addrconf_sysctl_register net/ipv6/addrconf.c:6897 [inline]
addrconf_sysctl_register+0x140/0x1e0 net/ipv6/addrconf.c:6886
ipv6_add_dev net/ipv6/addrconf.c:443 [inline]
ipv6_add_dev+0x9dd/0x10b0 net/ipv6/addrconf.c:363
addrconf_notify+0x89c/0x2270 net/ipv6/addrconf.c:3491
notifier_call_chain+0xc2/0x230 kernel/notifier.c:83
__raw_notifier_call_chain kernel/notifier.c:361 [inline]
raw_notifier_call_chain+0x2e/0x40 kernel/notifier.c:368
call_netdevice_notifiers_info net/core/dev.c:1893 [inline]
call_netdevice_notifiers_info+0xba/0x130 net/core/dev.c:1878
call_netdevice_notifiers_extack net/core/dev.c:1905 [inline]
call_netdevice_notifiers net/core/dev.c:1919 [inline]
register_netdevice+0x6de/0x1020 net/core/dev.c:9345
bond_newlink drivers/net/bonding/bond_netlink.c:458 [inline]
bond_newlink+0x4b/0x90 drivers/net/bonding/bond_netlink.c:448
__rtnl_newlink+0x109e/0x1790 net/core/rtnetlink.c:3305
rtnl_newlink+0x69/0xa0 net/core/rtnetlink.c:3363
rtnetlink_rcv_msg+0x45e/0xaf0 net/core/rtnetlink.c:5424
netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477
rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5442
netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
netlink_unicast+0x58c/0x7d0 net/netlink/af_netlink.c:1328
netlink_sendmsg+0x91c/0xea0 net/netlink/af_netlink.c:1917
sock_sendmsg_nosec net/socket.c:639 [inline]
sock_sendmsg+0xd7/0x130 net/socket.c:659
__sys_sendto+0x262/0x380 net/socket.c:1985
__do_sys_sendto net/socket.c:1997 [inline]
__se_sys_sendto net/socket.c:1993 [inline]
__x64_sys_sendto+0xe1/0x1a0 net/socket.c:1993
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff888090582000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1711 bytes inside of
2048-byte region [ffff888090582000, ffff888090582800)
The buggy address belongs to the page:
page:ffffea0002416080 refcount:1 mapcount:0 mapping:ffff8880aa400e00
raw: 00fffe0000000200 ffffea0002a06388 ffffea00025cd188 ffff8880aa400e00
raw: 0000000000000000 ffff888090582000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888090582580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888090582600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff888090582680: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
ffff888090582700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888090582780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

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