4.19-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 095faf45e64be00bff4da2d6182dface3d69c9b7 ]
There is a reference counter to ensure that masquerade modules register notifiers only once. However, the existing reference counter approach is not safe, test commands are:
while : do modprobe ip6t_MASQUERADE & modprobe nft_masq_ipv6 & modprobe -rv ip6t_MASQUERADE & modprobe -rv nft_masq_ipv6 & done
numbers below represent the reference counter. -------------------------------------------------------- CPU0 CPU1 CPU2 CPU3 CPU4 [insmod] [insmod] [rmmod] [rmmod] [insmod] -------------------------------------------------------- 0->1 register 1->2 returns 2->1 returns 1->0 0->1 register <-- unregister --------------------------------------------------------
The unregistation of CPU3 should be processed before the registration of CPU4.
In order to fix this, use a mutex instead of reference counter.
splat looks like: [ 323.869557] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [modprobe:1381] [ 323.869574] Modules linked in: nf_tables(+) nf_nat_ipv6(-) nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 n] [ 323.869574] irq event stamp: 194074 [ 323.898930] hardirqs last enabled at (194073): [<ffffffff90004a0d>] trace_hardirqs_on_thunk+0x1a/0x1c [ 323.898930] hardirqs last disabled at (194074): [<ffffffff90004a29>] trace_hardirqs_off_thunk+0x1a/0x1c [ 323.898930] softirqs last enabled at (182132): [<ffffffff922006ec>] __do_softirq+0x6ec/0xa3b [ 323.898930] softirqs last disabled at (182109): [<ffffffff90193426>] irq_exit+0x1a6/0x1e0 [ 323.898930] CPU: 0 PID: 1381 Comm: modprobe Not tainted 4.20.0-rc2+ #27 [ 323.898930] RIP: 0010:raw_notifier_chain_register+0xea/0x240 [ 323.898930] Code: 3c 03 0f 8e f2 00 00 00 44 3b 6b 10 7f 4d 49 bc 00 00 00 00 00 fc ff df eb 22 48 8d 7b 10 488 [ 323.898930] RSP: 0018:ffff888101597218 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13 [ 323.898930] RAX: 0000000000000000 RBX: ffffffffc04361c0 RCX: 0000000000000000 [ 323.898930] RDX: 1ffffffff26132ae RSI: ffffffffc04aa3c0 RDI: ffffffffc04361d0 [ 323.898930] RBP: ffffffffc04361c8 R08: 0000000000000000 R09: 0000000000000001 [ 323.898930] R10: ffff8881015972b0 R11: fffffbfff26132c4 R12: dffffc0000000000 [ 323.898930] R13: 0000000000000000 R14: 1ffff110202b2e44 R15: ffffffffc04aa3c0 [ 323.898930] FS: 00007f813ed41540(0000) GS:ffff88811ae00000(0000) knlGS:0000000000000000 [ 323.898930] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 323.898930] CR2: 0000559bf2c9f120 CR3: 000000010bc80000 CR4: 00000000001006f0 [ 323.898930] Call Trace: [ 323.898930] ? atomic_notifier_chain_register+0x2d0/0x2d0 [ 323.898930] ? down_read+0x150/0x150 [ 323.898930] ? sched_clock_cpu+0x126/0x170 [ 323.898930] ? nf_tables_core_module_init+0xe4/0xe4 [nf_tables] [ 323.898930] ? nf_tables_core_module_init+0xe4/0xe4 [nf_tables] [ 323.898930] register_netdevice_notifier+0xbb/0x790 [ 323.898930] ? __dev_close_many+0x2d0/0x2d0 [ 323.898930] ? __mutex_unlock_slowpath+0x17f/0x740 [ 323.898930] ? wait_for_completion+0x710/0x710 [ 323.898930] ? nf_tables_core_module_init+0xe4/0xe4 [nf_tables] [ 323.898930] ? up_write+0x6c/0x210 [ 323.898930] ? nf_tables_core_module_init+0xe4/0xe4 [nf_tables] [ 324.127073] ? nf_tables_core_module_init+0xe4/0xe4 [nf_tables] [ 324.127073] nft_chain_filter_init+0x1e/0xe8a [nf_tables] [ 324.127073] nf_tables_module_init+0x37/0x92 [nf_tables] [ ... ]
Fixes: 8dd33cc93ec9 ("netfilter: nf_nat: generalize IPv4 masquerading support for nf_tables") Fixes: be6b635cd674 ("netfilter: nf_nat: generalize IPv6 masquerading support for nf_tables") Signed-off-by: Taehee Yoo ap420073@gmail.com Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org
Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/netfilter/nf_nat_masquerade_ipv4.c | 23 ++++++++++++++------- net/ipv6/netfilter/nf_nat_masquerade_ipv6.c | 23 ++++++++++++++------- 2 files changed, 32 insertions(+), 14 deletions(-)
diff --git a/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c b/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c index 4a7c1f207d6e..4c7fcd32f8e6 100644 --- a/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c +++ b/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c @@ -131,15 +131,17 @@ static struct notifier_block masq_inet_notifier = { .notifier_call = masq_inet_event, };
-static atomic_t masquerade_notifier_refcount = ATOMIC_INIT(0); +static int masq_refcnt; +static DEFINE_MUTEX(masq_mutex);
int nf_nat_masquerade_ipv4_register_notifier(void) { - int ret; + int ret = 0;
+ mutex_lock(&masq_mutex); /* check if the notifier was already set */ - if (atomic_inc_return(&masquerade_notifier_refcount) > 1) - return 0; + if (++masq_refcnt > 1) + goto out_unlock;
/* Register for device down reports */ ret = register_netdevice_notifier(&masq_dev_notifier); @@ -150,22 +152,29 @@ int nf_nat_masquerade_ipv4_register_notifier(void) if (ret) goto err_unregister;
+ mutex_unlock(&masq_mutex); return ret; + err_unregister: unregister_netdevice_notifier(&masq_dev_notifier); err_dec: - atomic_dec(&masquerade_notifier_refcount); + masq_refcnt--; +out_unlock: + mutex_unlock(&masq_mutex); return ret; } EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4_register_notifier);
void nf_nat_masquerade_ipv4_unregister_notifier(void) { + mutex_lock(&masq_mutex); /* check if the notifier still has clients */ - if (atomic_dec_return(&masquerade_notifier_refcount) > 0) - return; + if (--masq_refcnt > 0) + goto out_unlock;
unregister_netdevice_notifier(&masq_dev_notifier); unregister_inetaddr_notifier(&masq_inet_notifier); +out_unlock: + mutex_unlock(&masq_mutex); } EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4_unregister_notifier); diff --git a/net/ipv6/netfilter/nf_nat_masquerade_ipv6.c b/net/ipv6/netfilter/nf_nat_masquerade_ipv6.c index 10012fc687b6..37b1d413c825 100644 --- a/net/ipv6/netfilter/nf_nat_masquerade_ipv6.c +++ b/net/ipv6/netfilter/nf_nat_masquerade_ipv6.c @@ -162,15 +162,17 @@ static struct notifier_block masq_inet6_notifier = { .notifier_call = masq_inet6_event, };
-static atomic_t masquerade_notifier_refcount = ATOMIC_INIT(0); +static int masq_refcnt; +static DEFINE_MUTEX(masq_mutex);
int nf_nat_masquerade_ipv6_register_notifier(void) { - int ret; + int ret = 0;
+ mutex_lock(&masq_mutex); /* check if the notifier is already set */ - if (atomic_inc_return(&masquerade_notifier_refcount) > 1) - return 0; + if (++masq_refcnt > 1) + goto out_unlock;
ret = register_netdevice_notifier(&masq_dev_notifier); if (ret) @@ -180,22 +182,29 @@ int nf_nat_masquerade_ipv6_register_notifier(void) if (ret) goto err_unregister;
+ mutex_unlock(&masq_mutex); return ret; + err_unregister: unregister_netdevice_notifier(&masq_dev_notifier); err_dec: - atomic_dec(&masquerade_notifier_refcount); + masq_refcnt--; +out_unlock: + mutex_unlock(&masq_mutex); return ret; } EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6_register_notifier);
void nf_nat_masquerade_ipv6_unregister_notifier(void) { + mutex_lock(&masq_mutex); /* check if the notifier still has clients */ - if (atomic_dec_return(&masquerade_notifier_refcount) > 0) - return; + if (--masq_refcnt > 0) + goto out_unlock;
unregister_inet6addr_notifier(&masq_inet6_notifier); unregister_netdevice_notifier(&masq_dev_notifier); +out_unlock: + mutex_unlock(&masq_mutex); } EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6_unregister_notifier);