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netfilter: conntrack: serialize hash resizes and cleanups

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Syzbot was able to trigger the following warning [1]

No repro found by syzbot yet but I was able to trigger similar issue
by having 2 scripts running in parallel, changing conntrack hash sizes,
and:

for j in `seq 1 1000` ; do unshare -n /bin/true >/dev/null ; done

It would take more than 5 minutes for net_namespace structures
to be cleaned up.

This is because nf_ct_iterate_cleanup() has to restart everytime
a resize happened.

By adding a mutex, we can serialize hash resizes and cleanups
and also make get_next_corpse() faster by skipping over empty
buckets.

Even without resizes in the picture, this patch considerably
speeds up network namespace dismantles.

[1]
INFO: task syz-executor.0:8312 can't die for more than 144 seconds.
task:syz-executor.0  state:R  running task     stack:25672 pid: 8312 ppid:  6573 flags:0x00004006
Call Trace:
 context_switch kernel/sched/core.c:4955 [inline]
 __schedule+0x940/0x26f0 kernel/sched/core.c:6236
 preempt_schedule_common+0x45/0xc0 kernel/sched/core.c:6408
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
 __local_bh_enable_ip+0x109/0x120 kernel/softirq.c:390
 local_bh_enable include/linux/bottom_half.h:32 [inline]
 get_next_corpse net/netfilter/nf_conntrack_core.c:2252 [inline]
 nf_ct_iterate_cleanup+0x15a/0x450 net/netfilter/nf_conntrack_core.c:2275
 nf_conntrack_cleanup_net_list+0x14c/0x4f0 net/netfilter/nf_conntrack_core.c:2469
 ops_exit_list+0x10d/0x160 net/core/net_namespace.c:171
 setup_net+0x639/0xa30 net/core/net_namespace.c:349
 copy_net_ns+0x319/0x760 net/core/net_namespace.c:470
 create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0xc1/0x1f0 kernel/nsproxy.c:226
 ksys_unshare+0x445/0x920 kernel/fork.c:3128
 __do_sys_unshare kernel/fork.c:3202 [inline]
 __se_sys_unshare kernel/fork.c:3200 [inline]
 __x64_sys_unshare+0x2d/0x40 kernel/fork.c:3200
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f63da68e739
RSP: 002b:00007f63d7c05188 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007f63da792f80 RCX: 00007f63da68e739
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 00007f63da6e8cc4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f63da792f80
R13: 00007fff50b75d3f R14: 00007f63d7c05300 R15: 0000000000022000

Showing all locks held in the system:
1 lock held by khungtaskd/27:
 #0: ffffffff8b980020 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6446
2 locks held by kworker/u4:2/153:
 #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
 #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline]
 #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:634 [inline]
 #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:661 [inline]
 #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2268
 #1: ffffc9000140fdb0 ((kfence_timer).work){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2272
1 lock held by systemd-udevd/2970:
1 lock held by in:imklog/6258:
 #0: ffff88807f970ff0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:990
3 locks held by kworker/1:6/8158:
1 lock held by syz-executor.0/8312:
2 locks held by kworker/u4:13/9320:
1 lock held by syz-executor.5/10178:
1 lock held by syz-executor.4/10217:

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Eric Dumazet 2021-09-17 15:15:56 -07:00 committed by Pablo Neira Ayuso
parent b53deef054
commit e9edc188fc
1 changed files with 37 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

70
net/netfilter/nf_conntrack_core.c
View File

@ -74,6 +74,9 @@ static __read_mostly struct kmem_cache *nf_conntrack_cachep;
static DEFINE_SPINLOCK(nf_conntrack_locks_all_lock);
static __read_mostly bool nf_conntrack_locks_all;
/* serialize hash resizes and nf_ct_iterate_cleanup */
static DEFINE_MUTEX(nf_conntrack_mutex);
#define GC_SCAN_INTERVAL (120u * HZ)
#define GC_SCAN_MAX_DURATION msecs_to_jiffies(10)
@ -2263,28 +2266,31 @@ get_next_corpse(int (*iter)(struct nf_conn *i, void *data),
spinlock_t *lockp;
for (; *bucket < nf_conntrack_htable_size; (*bucket)++) {
struct hlist_nulls_head *hslot = &nf_conntrack_hash[*bucket];
if (hlist_nulls_empty(hslot))
continue;
lockp = &nf_conntrack_locks[*bucket % CONNTRACK_LOCKS];
local_bh_disable();
nf_conntrack_lock(lockp);
if (*bucket < nf_conntrack_htable_size) {
hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[*bucket], hnnode) {
if (NF_CT_DIRECTION(h) != IP_CT_DIR_REPLY)
continue;
/* All nf_conn objects are added to hash table twice, one
* for original direction tuple, once for the reply tuple.
*
* Exception: In the IPS_NAT_CLASH case, only the reply
* tuple is added (the original tuple already existed for
* a different object).
*
* We only need to call the iterator once for each
* conntrack, so we just use the 'reply' direction
* tuple while iterating.
*/
ct = nf_ct_tuplehash_to_ctrack(h);
if (iter(ct, data))
goto found;
}
hlist_nulls_for_each_entry(h, n, hslot, hnnode) {
if (NF_CT_DIRECTION(h) != IP_CT_DIR_REPLY)
continue;
/* All nf_conn objects are added to hash table twice, one
* for original direction tuple, once for the reply tuple.
*
* Exception: In the IPS_NAT_CLASH case, only the reply
* tuple is added (the original tuple already existed for
* a different object).
*
* We only need to call the iterator once for each
* conntrack, so we just use the 'reply' direction
* tuple while iterating.
*/
ct = nf_ct_tuplehash_to_ctrack(h);
if (iter(ct, data))
goto found;
}
spin_unlock(lockp);
local_bh_enable();
@ -2302,26 +2308,20 @@ found:
static void nf_ct_iterate_cleanup(int (*iter)(struct nf_conn *i, void *data),
void *data, u32 portid, int report)
{
unsigned int bucket = 0, sequence;
unsigned int bucket = 0;
struct nf_conn *ct;
might_sleep();
for (;;) {
sequence = read_seqcount_begin(&nf_conntrack_generation);
mutex_lock(&nf_conntrack_mutex);
while ((ct = get_next_corpse(iter, data, &bucket)) != NULL) {
/* Time to push up daises... */
while ((ct = get_next_corpse(iter, data, &bucket)) != NULL) {
/* Time to push up daises... */
nf_ct_delete(ct, portid, report);
nf_ct_put(ct);
cond_resched();
}
if (!read_seqcount_retry(&nf_conntrack_generation, sequence))
break;
bucket = 0;
nf_ct_delete(ct, portid, report);
nf_ct_put(ct);
cond_resched();
}
mutex_unlock(&nf_conntrack_mutex);
}
struct iter_data {
@ -2557,8 +2557,10 @@ int nf_conntrack_hash_resize(unsigned int hashsize)
if (!hash)
return -ENOMEM;
mutex_lock(&nf_conntrack_mutex);
old_size = nf_conntrack_htable_size;
if (old_size == hashsize) {
mutex_unlock(&nf_conntrack_mutex);
kvfree(hash);
return 0;
}
@ -2598,6 +2600,8 @@ int nf_conntrack_hash_resize(unsigned int hashsize)
nf_conntrack_all_unlock();
local_bh_enable();
mutex_unlock(&nf_conntrack_mutex);
synchronize_net();
kvfree(old_hash);
return 0;