[PATCH 4.9 57/86] netfilter: IDLETIMER: be syzkaller friendly

Greg Kroah-Hartman
2018-03-16T15:23:20Z

From: Eric Dumazet <edumazet@google.com>

commit cfc2c740533368b96e2be5e0a4e8c3cace7d9814 upstream.

We had one report from syzkaller [1]

First issue is that INIT_WORK() should be done before mod_timer()
or we risk timer being fired too soon, even with a 1 second timer.

Second issue is that we need to reject too big info->timeout
to avoid overflows in msecs_to_jiffies(info->timeout * 1000), or
risk looping, if result after overflow is 0.

[1]
WARNING: CPU: 1 PID: 5129 at kernel/workqueue.c:1444 __queue_work+0xdf4/0x1230 kernel/workqueue.c:1444
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 5129 Comm: syzkaller159866 Not tainted 4.16.0-rc1+ #230
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
panic+0x1e4/0x41c kernel/panic.c:183
__warn+0x1dc/0x200 kernel/panic.c:547
report_bug+0x211/0x2d0 lib/bug.c:184
fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
fixup_bug arch/x86/kernel/traps.c:247 [inline]
do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:988
RIP: 0010:__queue_work+0xdf4/0x1230 kernel/workqueue.c:1444
RSP: 0018:ffff8801db507538 EFLAGS: 00010006
RAX: ffff8801aeb46080 RBX: ffff8801db530200 RCX: ffffffff81481404
RDX: 0000000000000100 RSI: ffffffff86b42640 RDI: 0000000000000082
RBP: ffff8801db507758 R08: 1ffff1003b6a0de5 R09: 000000000000000c
R10: ffff8801db5073f0 R11: 0000000000000020 R12: 1ffff1003b6a0eb6
R13: ffff8801b1067ae0 R14: 00000000000001f8 R15: dffffc0000000000
queue_work_on+0x16a/0x1c0 kernel/workqueue.c:1488
queue_work include/linux/workqueue.h:488 [inline]
schedule_work include/linux/workqueue.h:546 [inline]
idletimer_tg_expired+0x44/0x60 net/netfilter/xt_IDLETIMER.c:116
call_timer_fn+0x228/0x820 kernel/time/timer.c:1326
expire_timers kernel/time/timer.c:1363 [inline]
__run_timers+0x7ee/0xb70 kernel/time/timer.c:1666
run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692
__do_softirq+0x2d7/0xb85 kernel/softirq.c:285
invoke_softirq kernel/softirq.c:365 [inline]
irq_exit+0x1cc/0x200 kernel/softirq.c:405
exiting_irq arch/x86/include/asm/apic.h:541 [inline]
smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052
apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:829
</IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:777 [inline]
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x5e/0xba kernel/locking/spinlock.c:184
RSP: 0018:ffff8801c20173c8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff12
RAX: dffffc0000000000 RBX: 0000000000000282 RCX: 0000000000000006
RDX: 1ffffffff0d592cd RSI: 1ffff10035d68d23 RDI: 0000000000000282
RBP: ffff8801c20173d8 R08: 1ffff10038402e47 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff8820e5c8
R13: ffff8801b1067ad8 R14: ffff8801aea7c268 R15: ffff8801aea7c278
__debug_object_init+0x235/0x1040 lib/debugobjects.c:378
debug_object_init+0x17/0x20 lib/debugobjects.c:391
__init_work+0x2b/0x60 kernel/workqueue.c:506
idletimer_tg_create net/netfilter/xt_IDLETIMER.c:152 [inline]
idletimer_tg_checkentry+0x691/0xb00 net/netfilter/xt_IDLETIMER.c:213
xt_check_target+0x22c/0x7d0 net/netfilter/x_tables.c:850
check_target net/ipv6/netfilter/ip6_tables.c:533 [inline]
find_check_entry.isra.7+0x935/0xcf0 net/ipv6/netfilter/ip6_tables.c:575
translate_table+0xf52/0x1690 net/ipv6/netfilter/ip6_tables.c:744
do_replace net/ipv6/netfilter/ip6_tables.c:1160 [inline]
do_ip6t_set_ctl+0x370/0x5f0 net/ipv6/netfilter/ip6_tables.c:1686
nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115
ipv6_setsockopt+0x10b/0x130 net/ipv6/ipv6_sockglue.c:927
udpv6_setsockopt+0x45/0x80 net/ipv6/udp.c:1422
sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2976
SYSC_setsockopt net/socket.c:1850 [inline]
SyS_setsockopt+0x189/0x360 net/socket.c:1829
do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287

Fixes: 0902b469bd25 ("netfilter: xtables: idletimer target implementation")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/netfilter/xt_IDLETIMER.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

--- a/net/netfilter/xt_IDLETIMER.c
+++ b/net/netfilter/xt_IDLETIMER.c
@@ -147,11 +147,11 @@ static int idletimer_tg_create(struct id
(unsigned long) info->timer);
info->timer->refcnt = 1;

+ INIT_WORK(&info->timer->work, idletimer_tg_work);
+
mod_timer(&info->timer->timer,
msecs_to_jiffies(info->timeout * 1000) + jiffies);

- INIT_WORK(&info->timer->work, idletimer_tg_work);
-
return 0;

out_free_attr:
@@ -192,7 +192,10 @@ static int idletimer_tg_checkentry(const
pr_debug("timeout value is zero\n");
return -EINVAL;
}
-
+ if (info->timeout >= INT_MAX / 1000) {
+ pr_debug("timeout value is too big\n");
+ return -EINVAL;
+ }
if (info->label[0] == '\0' ||
strnlen(info->label,
MAX_IDLETIMER_LABEL_SIZE) == MAX_IDLETIMER_LABEL_SIZE) {