KASAN: use-after-free Read in dump_schedule

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fc3abb53 Merge branch 'for-linus' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17b672f5900000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1c560d0f4e121c9
dashboard link: https://syzkaller.appspot.com/bug?extid=621fd33c0b53d15ee8de
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1129d0e9900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17fb6a25900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+621fd3...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in dump_schedule+0x4b/0x850 net/sched/sch_taprio.c:1747
Read of size 8 at addr ffff88808f48cb40 by task syz-executor466/11250

CPU: 0 PID: 11250 Comm: syz-executor466 Not tainted 5.9.0-rc3-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+0x1d6/0x29e lib/dump_stack.c:118
print_address_description+0x66/0x620 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report+0x132/0x1d0 mm/kasan/report.c:530
dump_schedule+0x4b/0x850 net/sched/sch_taprio.c:1747
taprio_dump+0x701/0xcc0 net/sched/sch_taprio.c:1815
tc_fill_qdisc+0x5c5/0x1150 net/sched/sch_api.c:916
qdisc_notify+0x1df/0x370 net/sched/sch_api.c:983
tc_modify_qdisc+0x1b1a/0x1d90 net/sched/sch_api.c:1635
rtnetlink_rcv_msg+0x889/0xd40 net/core/rtnetlink.c:5563
netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2470
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1330
netlink_sendmsg+0xa57/0xd70 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg net/socket.c:671 [inline]
kernel_sendmsg+0xe2/0x120 net/socket.c:691
sock_no_sendpage+0xe0/0x120 net/core/sock.c:2852
kernel_sendpage net/socket.c:3642 [inline]
sock_sendpage+0xd0/0x120 net/socket.c:944
pipe_to_sendpage+0x208/0x2d0 fs/splice.c:448
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x351/0x8b0 fs/splice.c:626
splice_from_pipe fs/splice.c:661 [inline]
generic_splice_sendpage+0x112/0x180 fs/splice.c:834
do_splice_from fs/splice.c:846 [inline]
do_splice+0xdd1/0x1a50 fs/splice.c:1144
__do_sys_splice fs/splice.c:1419 [inline]
__se_sys_splice fs/splice.c:1401 [inline]
__x64_sys_splice+0x14f/0x1f0 fs/splice.c:1401
do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x449fa9
Code: e8 9c e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 bb 04 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fa469406d88 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00000000006e0c48 RCX: 0000000000449fa9
RDX: 0000000000000004 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000006e0c40 R08: 0000000000010973 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e0c4c
R13: 140b0024000000a4 R14: 0000000000000000 R15: 000000306d616574

Allocated by task 11229:
kasan_save_stack mm/kasan/common.c:48 [inline]
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc+0x100/0x130 mm/kasan/common.c:461
kmem_cache_alloc_trace+0x1e4/0x2e0 mm/slab.c:3550
kmalloc include/linux/slab.h:554 [inline]
kzalloc include/linux/slab.h:666 [inline]
taprio_change+0x3b5/0x5200 net/sched/sch_taprio.c:1436
qdisc_change net/sched/sch_api.c:1331 [inline]
tc_modify_qdisc+0x1793/0x1d90 net/sched/sch_api.c:1633
rtnetlink_rcv_msg+0x889/0xd40 net/core/rtnetlink.c:5563
netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2470
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1330
netlink_sendmsg+0xa57/0xd70 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg net/socket.c:671 [inline]
kernel_sendmsg+0xe2/0x120 net/socket.c:691
sock_no_sendpage+0xe0/0x120 net/core/sock.c:2852
kernel_sendpage net/socket.c:3642 [inline]
sock_sendpage+0xd0/0x120 net/socket.c:944
pipe_to_sendpage+0x208/0x2d0 fs/splice.c:448
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x351/0x8b0 fs/splice.c:626
splice_from_pipe fs/splice.c:661 [inline]
generic_splice_sendpage+0x112/0x180 fs/splice.c:834
do_splice_from fs/splice.c:846 [inline]
do_splice+0xdd1/0x1a50 fs/splice.c:1144
__do_sys_splice fs/splice.c:1419 [inline]
__se_sys_splice fs/splice.c:1401 [inline]
__x64_sys_splice+0x14f/0x1f0 fs/splice.c:1401
do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 9:
kasan_save_stack mm/kasan/common.c:48 [inline]
kasan_set_track+0x3d/0x70 mm/kasan/common.c:56
kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355
__kasan_slab_free+0xdd/0x110 mm/kasan/common.c:422
__cache_free mm/slab.c:3418 [inline]
kfree+0x113/0x200 mm/slab.c:3756
rcu_do_batch kernel/rcu/tree.c:2428 [inline]
rcu_core+0x79b/0x1130 kernel/rcu/tree.c:2656
__do_softirq+0x256/0x6d5 kernel/softirq.c:298

Last call_rcu():
kasan_save_stack+0x27/0x50 mm/kasan/common.c:48
kasan_record_aux_stack+0x7b/0xb0 mm/kasan/generic.c:346
__call_rcu kernel/rcu/tree.c:2894 [inline]
call_rcu+0x141/0x830 kernel/rcu/tree.c:2968
taprio_change+0x4202/0x5200 net/sched/sch_taprio.c:1554
qdisc_change net/sched/sch_api.c:1331 [inline]
tc_modify_qdisc+0x1793/0x1d90 net/sched/sch_api.c:1633
rtnetlink_rcv_msg+0x889/0xd40 net/core/rtnetlink.c:5563
netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2470
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1330
netlink_sendmsg+0xa57/0xd70 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg net/socket.c:671 [inline]
kernel_sendmsg+0xe2/0x120 net/socket.c:691
sock_no_sendpage+0xe0/0x120 net/core/sock.c:2852
kernel_sendpage net/socket.c:3642 [inline]
sock_sendpage+0xd0/0x120 net/socket.c:944
pipe_to_sendpage+0x208/0x2d0 fs/splice.c:448
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x351/0x8b0 fs/splice.c:626
splice_from_pipe fs/splice.c:661 [inline]
generic_splice_sendpage+0x112/0x180 fs/splice.c:834
do_splice_from fs/splice.c:846 [inline]
do_splice+0xdd1/0x1a50 fs/splice.c:1144
__do_sys_splice fs/splice.c:1419 [inline]
__se_sys_splice fs/splice.c:1401 [inline]
__x64_sys_splice+0x14f/0x1f0 fs/splice.c:1401
do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Second to last call_rcu():
kasan_save_stack+0x27/0x50 mm/kasan/common.c:48
kasan_record_aux_stack+0x7b/0xb0 mm/kasan/generic.c:346
__call_rcu kernel/rcu/tree.c:2894 [inline]
call_rcu+0x141/0x830 kernel/rcu/tree.c:2968
taprio_change+0x4202/0x5200 net/sched/sch_taprio.c:1554
qdisc_change net/sched/sch_api.c:1331 [inline]
tc_modify_qdisc+0x1793/0x1d90 net/sched/sch_api.c:1633
rtnetlink_rcv_msg+0x889/0xd40 net/core/rtnetlink.c:5563
netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2470
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1330
netlink_sendmsg+0xa57/0xd70 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg net/socket.c:671 [inline]
kernel_sendmsg+0xe2/0x120 net/socket.c:691
sock_no_sendpage+0xe0/0x120 net/core/sock.c:2852
kernel_sendpage net/socket.c:3642 [inline]
sock_sendpage+0xd0/0x120 net/socket.c:944
pipe_to_sendpage+0x208/0x2d0 fs/splice.c:448
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x351/0x8b0 fs/splice.c:626
splice_from_pipe fs/splice.c:661 [inline]
generic_splice_sendpage+0x112/0x180 fs/splice.c:834
do_splice_from fs/splice.c:846 [inline]
do_splice+0xdd1/0x1a50 fs/splice.c:1144
__do_sys_splice fs/splice.c:1419 [inline]
__se_sys_splice fs/splice.c:1401 [inline]
__x64_sys_splice+0x14f/0x1f0 fs/splice.c:1401
do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff88808f48cb00
which belongs to the cache kmalloc-96 of size 96
The buggy address is located 64 bytes inside of
96-byte region [ffff88808f48cb00, ffff88808f48cb60)
The buggy address belongs to the page:
page:00000000cae6299d refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88808f48cd00 pfn:0x8f48c
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002761e08 ffffea000275d888 ffff8880aa440300
raw: ffff88808f48cd00 ffff88808f48c000 000000010000001a 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808f48ca00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff88808f48ca80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff88808f48cb00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
^
ffff88808f48cb80: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
ffff88808f48cc00: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
==================================================================


---
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syzbot can test patches for this issue, for details see:
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[syzbot]

syzbot has bisected this issue to:

commit 7b9eba7ba0c1b24df42b70b62d154b284befbccf
Author: Leandro Dorileo <leandro.mac...@intel.com>
Date: Mon Apr 8 17:12:17 2019 +0000

net/sched: taprio: fix picos_per_byte miscalculation

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15464af9900000
start commit: fc3abb53 Merge branch 'for-linus' of git://git.kernel.org/..
git tree: upstream
final oops: https://syzkaller.appspot.com/x/report.txt?x=17464af9900000
console output: https://syzkaller.appspot.com/x/log.txt?x=13464af9900000

kernel config: https://syzkaller.appspot.com/x/.config?x=e1c560d0f4e121c9
dashboard link: https://syzkaller.appspot.com/bug?extid=621fd33c0b53d15ee8de

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1129d0e9900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17fb6a25900000

Reported-by: syzbot+621fd3...@syzkaller.appspotmail.com
Fixes: 7b9eba7ba0c1 ("net/sched: taprio: fix picos_per_byte miscalculation")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in dump_schedule

==================================================================
BUG: KASAN: use-after-free in dump_schedule+0x758/0x7d0 net/sched/sch_taprio.c:1764
Read of size 8 at addr ffff88809f8a7dc0 by task syz-executor.2/17047

CPU: 1 PID: 17047 Comm: syz-executor.2 Not tainted 5.9.0-rc3-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+0x198/0x1fd lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
dump_schedule+0x758/0x7d0 net/sched/sch_taprio.c:1764
taprio_dump+0x55d/0xce0 net/sched/sch_taprio.c:1833
tc_fill_qdisc+0x5e7/0x1220 net/sched/sch_api.c:916
qdisc_notify.isra.0+0x2b1/0x310 net/sched/sch_api.c:983
tc_modify_qdisc+0xf45/0x1990 net/sched/sch_api.c:1635
rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5563
netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2470
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:671
sock_no_sendpage+0xee/0x130 net/core/sock.c:2852
kernel_sendpage net/socket.c:3642 [inline]
sock_sendpage+0xe5/0x140 net/socket.c:944
pipe_to_sendpage+0x2ad/0x380 fs/splice.c:448
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x3dc/0x830 fs/splice.c:626
splice_from_pipe fs/splice.c:661 [inline]
generic_splice_sendpage+0xd4/0x140 fs/splice.c:834
do_splice_from fs/splice.c:846 [inline]
do_splice+0xbcd/0x1820 fs/splice.c:1144

__do_sys_splice fs/splice.c:1419 [inline]
__se_sys_splice fs/splice.c:1401 [inline]

__x64_sys_splice+0x198/0x250 fs/splice.c:1401
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d5b9
Code: 5d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f4ae7fb3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 0000000000033980 RCX: 000000000045d5b9

RDX: 0000000000000004 RSI: 0000000000000000 RDI: 0000000000000003

RBP: 000000000118cf98 R08: 0000000000010973 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffd27e733ff R14: 00007f4ae7fb49c0 R15: 000000000118cf4c

Allocated by task 17033:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
kmem_cache_alloc_trace+0x174/0x2c0 mm/slab.c:3550

kmalloc include/linux/slab.h:554 [inline]
kzalloc include/linux/slab.h:666 [inline]

taprio_change+0x59f/0x2b50 net/sched/sch_taprio.c:1454
qdisc_change net/sched/sch_api.c:1331 [inline]
tc_modify_qdisc+0xd41/0x1990 net/sched/sch_api.c:1633
rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5563
netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2470
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:671
sock_no_sendpage+0xee/0x130 net/core/sock.c:2852
kernel_sendpage net/socket.c:3642 [inline]
sock_sendpage+0xe5/0x140 net/socket.c:944
pipe_to_sendpage+0x2ad/0x380 fs/splice.c:448
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x3dc/0x830 fs/splice.c:626
splice_from_pipe fs/splice.c:661 [inline]
generic_splice_sendpage+0xd4/0x140 fs/splice.c:834
do_splice_from fs/splice.c:846 [inline]
do_splice+0xbcd/0x1820 fs/splice.c:1144

__do_sys_splice fs/splice.c:1419 [inline]
__se_sys_splice fs/splice.c:1401 [inline]

__x64_sys_splice+0x198/0x250 fs/splice.c:1401
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 17046:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
__kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
__cache_free mm/slab.c:3418 [inline]
kfree+0x10e/0x2b0 mm/slab.c:3756
taprio_free_sched_cb+0x18b/0x240 net/sched/sch_taprio.c:124
rcu_do_batch kernel/rcu/tree.c:2428 [inline]
rcu_core+0x5ca/0x1130 kernel/rcu/tree.c:2656
__do_softirq+0x1f7/0xa91 kernel/softirq.c:298

Last call_rcu():
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_record_aux_stack+0x82/0xb0 mm/kasan/generic.c:346
__call_rcu kernel/rcu/tree.c:2894 [inline]
call_rcu+0x15e/0x7b0 kernel/rcu/tree.c:2968
taprio_change+0x2102/0x2b50 net/sched/sch_taprio.c:1572
qdisc_change net/sched/sch_api.c:1331 [inline]
tc_modify_qdisc+0xd41/0x1990 net/sched/sch_api.c:1633
rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5563
netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2470
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:671
sock_no_sendpage+0xee/0x130 net/core/sock.c:2852
kernel_sendpage net/socket.c:3642 [inline]
sock_sendpage+0xe5/0x140 net/socket.c:944
pipe_to_sendpage+0x2ad/0x380 fs/splice.c:448
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x3dc/0x830 fs/splice.c:626
splice_from_pipe fs/splice.c:661 [inline]
generic_splice_sendpage+0xd4/0x140 fs/splice.c:834
do_splice_from fs/splice.c:846 [inline]
do_splice+0xbcd/0x1820 fs/splice.c:1144

__do_sys_splice fs/splice.c:1419 [inline]
__se_sys_splice fs/splice.c:1401 [inline]

__x64_sys_splice+0x198/0x250 fs/splice.c:1401
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff88809f8a7d80

which belongs to the cache kmalloc-96 of size 96
The buggy address is located 64 bytes inside of

96-byte region [ffff88809f8a7d80, ffff88809f8a7de0)

The buggy address belongs to the page:

page:000000005b41dbbb refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88809f8a7f80 pfn:0x9f8a7
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00029f6108 ffffea00029adf08 ffff8880aa040300
raw: ffff88809f8a7f80 ffff88809f8a7000 000000010000001c 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff88809f8a7c80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff88809f8a7d00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff88809f8a7d80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
^
ffff88809f8a7e00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff88809f8a7e80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================


Tested on:

commit: dd9fb9bb Merge tags 'auxdisplay-for-linus-v5.9-rc4', 'clan..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=14f7c159900000
kernel config: https://syzkaller.appspot.com/x/.config?x=bd46548257448703
dashboard link: https://syzkaller.appspot.com/bug?extid=621fd33c0b53d15ee8de
compiler: gcc (GCC) 10.1.0-syz 20200507

[syzbot]

syzbot suspects this issue was fixed by commit:

commit cc00bcaa589914096edef7fb87ca5cee4a166b5c
Author: Subash Abhinov Kasiviswanathan <suba...@codeaurora.org>
Date: Wed Nov 25 18:27:22 2020 +0000

netfilter: x_tables: Switch synchronization to RCU

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10879d68d00000
start commit: 59126901 Merge tag 'perf-tools-fixes-for-v5.9-2020-09-03' ..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=3c5f6ce8d5b68299
dashboard link: https://syzkaller.appspot.com/bug?extid=621fd33c0b53d15ee8de
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=152c3af9900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12213b71900000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: netfilter: x_tables: Switch synchronization to RCU

[Dmitry Vyukov]