KASAN: slab-out-of-bounds Read in tun_net_xmit (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 8f19f12bdcc6 selftests: in udpgso_bench do not test udp ze..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=153c0c44400000
kernel config: https://syzkaller.appspot.com/x/.config?x=b88de6eac8694da6
dashboard link: https://syzkaller.appspot.com/bug?extid=8993c0fa96d57c399735
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+8993c0...@syzkaller.appspotmail.com

RDX: 0000000020000000 RSI: 00000000000089e1 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000014
R13: 00000000004bfe58 R14: 00000000004cf778 R15: 0000000000000001
==================================================================
BUG: KASAN: slab-out-of-bounds in __ptr_ring_produce
include/linux/ptr_ring.h:110 [inline]
BUG: KASAN: slab-out-of-bounds in ptr_ring_produce
include/linux/ptr_ring.h:133 [inline]
BUG: KASAN: slab-out-of-bounds in tun_net_xmit+0x1b28/0x1cd0
drivers/net/tun.c:1119
Read of size 8 at addr ffff8801d7356888 by task syz-executor3/4560

CPU: 0 PID: 4560 Comm: syz-executor3 Not tainted 4.18.0-rc3+ #8
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
__ptr_ring_produce include/linux/ptr_ring.h:110 [inline]
ptr_ring_produce include/linux/ptr_ring.h:133 [inline]
tun_net_xmit+0x1b28/0x1cd0 drivers/net/tun.c:1119
__netdev_start_xmit include/linux/netdevice.h:4148 [inline]
netdev_start_xmit include/linux/netdevice.h:4157 [inline]
xmit_one net/core/dev.c:3034 [inline]
dev_hard_start_xmit+0x26c/0xc30 net/core/dev.c:3050
sch_direct_xmit+0x486/0x1140 net/sched/sch_generic.c:327
qdisc_restart net/sched/sch_generic.c:390 [inline]
__qdisc_run+0x619/0x19f0 net/sched/sch_generic.c:398
qdisc_run include/net/pkt_sched.h:118 [inline]
__dev_xmit_skb net/core/dev.c:3229 [inline]
__dev_queue_xmit+0x13ec/0x38e0 net/core/dev.c:3537
dev_queue_xmit+0x17/0x20 net/core/dev.c:3602
neigh_hh_output include/net/neighbour.h:473 [inline]
neigh_output include/net/neighbour.h:481 [inline]
ip6_finish_output2+0x135a/0x2820 net/ipv6/ip6_output.c:120
ip6_finish_output+0x5fe/0xbc0 net/ipv6/ip6_output.c:154
NF_HOOK_COND include/linux/netfilter.h:276 [inline]
ip6_output+0x234/0x9d0 net/ipv6/ip6_output.c:171
dst_output include/net/dst.h:444 [inline]
NF_HOOK include/linux/netfilter.h:287 [inline]
mld_sendpack+0xaeb/0xfc0 net/ipv6/mcast.c:1658
mld_send_cr net/ipv6/mcast.c:1954 [inline]
mld_ifc_timer_expire+0x447/0x8a0 net/ipv6/mcast.c:2453
call_timer_fn+0x242/0x970 kernel/time/timer.c:1326
expire_timers kernel/time/timer.c:1363 [inline]
__run_timers+0x7a6/0xc70 kernel/time/timer.c:1666
run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692
__do_softirq+0x2e8/0xb17 kernel/softirq.c:288
invoke_softirq kernel/softirq.c:368 [inline]
irq_exit+0x1d1/0x200 kernel/softirq.c:408
exiting_irq arch/x86/include/asm/apic.h:527 [inline]
smp_apic_timer_interrupt+0x186/0x730 arch/x86/kernel/apic/apic.c:1052
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
</IRQ>
RIP: 0010:__mark_inode_dirty+0x719/0x1550 fs/fs-writeback.c:2147
Code: 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0
03 38 d0 7c 08 84 d2 0f 85 d5 09 00 00 8b 05 f7 17 d4 08 <48> 8d 8b 88 00
00 00 31 ff 49 89 ce 89 c6 89 85 a0 fd ff ff e8 de
RSP: 0018:ffff8801a2887930 EFLAGS: 00000297 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: ffff88019f664b60 RCX: ffffffff81d170cb
RDX: 0000000000000004 RSI: ffffffff81d175b2 RDI: ffffffff8aa58de0
RBP: ffff8801a2887b98 R08: ffff8801a287e000 R09: ffffed003b5c46d6
R10: ffffed003b5c46d6 R11: ffff8801dae236b3 R12: 0000000000000001
R13: 0000000000000001 R14: 0000000000000000 R15: ffff88019f664c38
generic_update_time+0x26a/0x450 fs/inode.c:1643
update_time fs/inode.c:1659 [inline]
touch_atime+0x29e/0x320 fs/inode.c:1731
file_accessed include/linux/fs.h:2082 [inline]
iterate_dir+0x394/0x5d0 fs/readdir.c:56
__do_sys_getdents fs/readdir.c:231 [inline]
__se_sys_getdents fs/readdir.c:212 [inline]
__x64_sys_getdents+0x29f/0x510 fs/readdir.c:212
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x453fbb
Code: 02 74 b6 31 f6 eb b9 0f 1f 84 00 00 00 00 00 41 57 41 56 48 63 ff 41
55 41 54 b8 4e 00 00 00 55 53 48 89 f3 48 83 ec 08 0f 05 <48> 3d 00 f0 ff
ff 77 55 4c 8d 24 06 49 89 c5 4c 39 e6 73 33 90 0f
RSP: 002b:0000000000a3d980 EFLAGS: 00000202 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 0000000001bfc970 RCX: 0000000000453fbb
RDX: 0000000000008000 RSI: 0000000001bfc970 RDI: 0000000000000013
RBP: 0000000001bfc970 R08: 0000000000000001 R09: 0000000001bfb940
R10: 0000000000000000 R11: 0000000000000202 R12: ffffffffffffffd4
R13: 0000000000000016 R14: 0000000000a3f160 R15: 0000000000702140

Allocated by task 12926:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
__do_kmalloc_node mm/slab.c:3682 [inline]
__kmalloc_node+0x47/0x70 mm/slab.c:3689
kmalloc_node include/linux/slab.h:555 [inline]
kvmalloc_node+0x65/0xf0 mm/util.c:423
kvmalloc include/linux/mm.h:557 [inline]
kvmalloc_array include/linux/mm.h:575 [inline]
__ptr_ring_init_queue_alloc include/linux/ptr_ring.h:475 [inline]
ptr_ring_resize_multiple include/linux/ptr_ring.h:635 [inline]
tun_queue_resize drivers/net/tun.c:3444 [inline]
tun_device_event+0x567/0x1030 drivers/net/tun.c:3463
notifier_call_chain+0x180/0x390 kernel/notifier.c:93
__raw_notifier_call_chain kernel/notifier.c:394 [inline]
raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1735
call_netdevice_notifiers net/core/dev.c:1753 [inline]
dev_change_tx_queue_len+0x192/0x270 net/core/dev.c:7150
do_setlink+0xccb/0x3e10 net/core/rtnetlink.c:2398
rtnl_group_changelink net/core/rtnetlink.c:2834 [inline]
rtnl_newlink+0x159a/0x1d60 net/core/rtnetlink.c:2992
rtnetlink_rcv_msg+0x46e/0xc30 net/core/rtnetlink.c:4662
netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2448
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4680
netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
netlink_unicast+0x5a0/0x760 net/netlink/af_netlink.c:1336
netlink_sendmsg+0xa18/0xfd0 net/netlink/af_netlink.c:1901
sock_sendmsg_nosec net/socket.c:641 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:651
___sys_sendmsg+0x7fd/0x930 net/socket.c:2125
__sys_sendmsg+0x11d/0x290 net/socket.c:2163
__do_sys_sendmsg net/socket.c:2172 [inline]
__se_sys_sendmsg net/socket.c:2170 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2170
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2418:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xd9/0x260 mm/slab.c:3813
kernfs_fop_write+0x18c/0x480 fs/kernfs/file.c:330
__vfs_write+0x117/0x9f0 fs/read_write.c:485
vfs_write+0x1f8/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801d7356880
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 8 bytes inside of
32-byte region [ffff8801d7356880, ffff8801d73568a0)
The buggy address belongs to the page:
page:ffffea00075cd580 count:1 mapcount:0 mapping:ffff8801da8001c0
index:0xffff8801d7356fc1
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea00075b4b08 ffffea0007510888 ffff8801da8001c0
raw: ffff8801d7356fc1 ffff8801d7356000 0000000100000037 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d7356780: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff8801d7356800: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
> ffff8801d7356880: 00 fc fc fc fc fc fc fc 00 00 00 fc fc fc fc fc
^
ffff8801d7356900: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff8801d7356980: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================


---
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[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: b71acb0e3721 Merge branch 'linus' of git://git.kernel.org/..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=14494353400000
kernel config: https://syzkaller.appspot.com/x/.config?x=4b137b8ba637eb77

dashboard link: https://syzkaller.appspot.com/bug?extid=8993c0fa96d57c399735
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11a01577400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=174baeab400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+8993c0...@syzkaller.appspotmail.com

IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready
8021q: adding VLAN 0 to HW filter on device batadv0
nf_conntrack: default automatic helper assignment has been turned off for
security reasons and CT-based firewall rule not found. Use the iptables CT
target to attach helpers instead.

==================================================================
BUG: KASAN: slab-out-of-bounds in __ptr_ring_produce
include/linux/ptr_ring.h:110 [inline]
BUG: KASAN: slab-out-of-bounds in ptr_ring_produce
include/linux/ptr_ring.h:133 [inline]

BUG: KASAN: slab-out-of-bounds in tun_net_xmit+0x197e/0x1be0
drivers/net/tun.c:1119
Read of size 8 at addr ffff88809fa64f48 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.20.0+ #363

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]

dump_stack+0x1d3/0x2c6 lib/dump_stack.c:113
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_load8_noabort+0x14/0x20 mm/kasan/report.c:433
__ptr_ring_produce include/linux/ptr_ring.h:110 [inline]
ptr_ring_produce include/linux/ptr_ring.h:133 [inline]

tun_net_xmit+0x197e/0x1be0 drivers/net/tun.c:1119
__netdev_start_xmit include/linux/netdevice.h:4382 [inline]
netdev_start_xmit include/linux/netdevice.h:4391 [inline]
xmit_one net/core/dev.c:3278 [inline]
dev_hard_start_xmit+0x286/0xc80 net/core/dev.c:3294
sch_direct_xmit+0x48b/0x1130 net/sched/sch_generic.c:327
qdisc_restart net/sched/sch_generic.c:390 [inline]
__qdisc_run+0x624/0x19f0 net/sched/sch_generic.c:398
qdisc_run include/net/pkt_sched.h:121 [inline]
__dev_xmit_skb net/core/dev.c:3473 [inline]
__dev_queue_xmit+0x190c/0x3ac0 net/core/dev.c:3832
dev_queue_xmit+0x17/0x20 net/core/dev.c:3897
neigh_hh_output include/net/neighbour.h:498 [inline]
neigh_output include/net/neighbour.h:506 [inline]
ip6_finish_output2+0x144e/0x2930 net/ipv6/ip6_output.c:120
ip6_finish_output+0x583/0xc50 net/ipv6/ip6_output.c:154
NF_HOOK_COND include/linux/netfilter.h:278 [inline]
ip6_output+0x232/0x9d0 net/ipv6/ip6_output.c:171
dst_output include/net/dst.h:444 [inline]
NF_HOOK include/linux/netfilter.h:289 [inline]
mld_sendpack+0xac9/0xfa0 net/ipv6/mcast.c:1683
mld_send_initial_cr.part.32+0x114/0x160 net/ipv6/mcast.c:2100
mld_send_initial_cr net/ipv6/mcast.c:2084 [inline]
mld_dad_timer_expire+0x42/0x1b0 net/ipv6/mcast.c:2119
call_timer_fn+0x272/0x920 kernel/time/timer.c:1325
expire_timers kernel/time/timer.c:1362 [inline]
__run_timers+0x7e5/0xc70 kernel/time/timer.c:1681
run_timer_softirq+0x52/0xb0 kernel/time/timer.c:1694
__do_softirq+0x30c/0xb2e kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x17f/0x1c0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1062
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
</IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:58
Code: e9 2c ff ff ff 48 89 c7 48 89 45 d8 e8 a3 84 c9 f9 48 8b 45 d8 e9 ca
fe ff ff 48 89 df e8 92 84 c9 f9 eb 82 55 48 89 e5 fb f4 <5d> c3 0f 1f 84
00 00 00 00 00 55 48 89 e5 f4 5d c3 90 90 90 90 90
RSP: 0018:ffffffff89607c20 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 1ffffffff12c0f88 RCX: 0000000000000000
RDX: 1ffffffff12e4969 RSI: 0000000000000001 RDI: ffffffff89724b48
RBP: ffffffff89607c20 R08: ffffffff8967aec0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff89607ce0
R13: ffffffff8a3a3260 R14: 0000000000000000 R15: 0000000000000000
arch_safe_halt arch/x86/include/asm/paravirt.h:156 [inline]
default_idle+0xbf/0x490 arch/x86/kernel/process.c:564
arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:555
default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x3db/0x5b0 kernel/sched/idle.c:262
cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:353
rest_init+0x243/0x372 init/main.c:443
arch_call_rest_init+0xe/0x1b
start_kernel+0x873/0x8ae init/main.c:741
x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

Allocated by task 7497:

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:3684 [inline]
__kmalloc_node+0x50/0x70 mm/slab.c:3691
kmalloc_node include/linux/slab.h:589 [inline]
kvmalloc_node+0x65/0xf0 mm/util.c:416
kvmalloc include/linux/mm.h:577 [inline]
kvmalloc_array include/linux/mm.h:595 [inline]

__ptr_ring_init_queue_alloc include/linux/ptr_ring.h:475 [inline]
ptr_ring_resize_multiple include/linux/ptr_ring.h:635 [inline]
tun_queue_resize drivers/net/tun.c:3606 [inline]

tun_device_event+0x56a/0x106c drivers/net/tun.c:3625
notifier_call_chain+0x17e/0x380 kernel/notifier.c:93

__raw_notifier_call_chain kernel/notifier.c:394 [inline]
raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401

call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1739
call_netdevice_notifiers_extack net/core/dev.c:1751 [inline]
call_netdevice_notifiers net/core/dev.c:1765 [inline]
dev_change_tx_queue_len+0x188/0x270 net/core/dev.c:7742
dev_ifsioc+0x79b/0xa80 net/core/dev_ioctl.c:287
dev_ioctl+0x1b5/0xcc0 net/core/dev_ioctl.c:488
sock_do_ioctl+0x1f6/0x420 net/socket.c:973
sock_ioctl+0x313/0x690 net/socket.c:1074
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4400:

save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]

__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521

kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]

kfree+0xcf/0x230 mm/slab.c:3817
single_release+0x8f/0xb0 fs/seq_file.c:597
__fput+0x385/0xa30 fs/file_table.c:278
____fput+0x15/0x20 fs/file_table.c:309
task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88809fa64f40

which belongs to the cache kmalloc-32 of size 32
The buggy address is located 8 bytes inside of

32-byte region [ffff88809fa64f40, ffff88809fa64f60)

The buggy address belongs to the page:

page:ffffea00027e9900 count:1 mapcount:0 mapping:ffff88812c3f01c0
index:0xffff88809fa64fc1
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002837048 ffffea00028f0888 ffff88812c3f01c0
raw: ffff88809fa64fc1 ffff88809fa64000 000000010000003f 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff88809fa64e00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff88809fa64e80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
> ffff88809fa64f00: fb fb fb fb fc fc fc fc 00 fc fc fc fc fc fc fc
^
ffff88809fa64f80: 06 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88809fa65000: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
==================================================================

[Jesper Dangaard Brouer]

Hi MST and Jason,

Could you please take a look at this? This bug is caused by a thread
resizing the tun-queue (via tun_queue_resize -> ptr_ring_resize_multiple).
And error happens in tun_net_xmit -> ptr_ring_produce. My guess is bug
happens when reading r->queue in ptr_ring_produce.

I've look at the code (see diff comments below), but I cannot spot the
issue as the (implicit) memory barrier of a spinlock should cover the
cases I can imagine.

diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
index 6894976b54e3..75a262d274bb 100644
--- a/include/linux/ptr_ring.h
+++ b/include/linux/ptr_ring.h
@@ -107,6 +107,12 @@ static inline bool ptr_ring_full_bh(struct ptr_ring *r)
*/
static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr)
{
+ barrier(); // Compiler barrier, should not be needed as
+ // spinlock are suppose-to-be a full barrier
+
+ // r->queue array can be kvfree'ed by ptr_ring_resize_multiple
+ // and reassigned by __ptr_ring_swap_queue, it should be safe
+ // as everything is called inder r->producer_lock spinlock.
if (unlikely(!r->size) || r->queue[r->producer])
return -ENOSPC;

@@ -578,6 +584,8 @@ static inline void **__ptr_ring_swap_queue(struct ptr_ring *r, void **queue,
r->consumer_head = 0;
r->consumer_tail = 0;
old = r->queue;
+ // Do we need some WRITE_ONCE for r->queue assignmment?
+ // or smp_wmb()
r->queue = queue;

return old;
@@ -640,6 +648,7 @@ static inline int ptr_ring_resize_multiple(struct ptr_ring **rings,
for (i = 0; i < nrings; ++i) {
spin_lock_irqsave(&(rings[i])->consumer_lock, flags);
spin_lock(&(rings[i])->producer_lock);
+ // happens under lock(s)
queues[i] = __ptr_ring_swap_queue(rings[i], queues[i],
size, gfp, destroy);
spin_unlock(&(rings[i])->producer_lock);
@@ -647,7 +656,7 @@ static inline int ptr_ring_resize_multiple(struct ptr_ring **rings,
}

for (i = 0; i < nrings; ++i)
- kvfree(queues[i]);
+ kvfree(queues[i]); // old r->queue is free'ed here

kfree(queues);

--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer

[Jason Wang]

On 2018/12/31 下午5:51, Jesper Dangaard Brouer wrote:
> Hi MST and Jason,
>
> Could you please take a look at this? This bug is caused by a thread
> resizing the tun-queue (via tun_queue_resize -> ptr_ring_resize_multiple).
> And error happens in tun_net_xmit -> ptr_ring_produce. My guess is bug
> happens when reading r->queue in ptr_ring_produce.
>
> I've look at the code (see diff comments below), but I cannot spot the
> issue as the (implicit) memory barrier of a spinlock should cover the
> cases I can imagine.

Hi:

Cong sent a patch for this and looks like it was fixed in
https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=aff6db454599d62191aabc208930e891748e4322.

Thanks