Le mardi 16 février 2010 à 15:55 +0100, Patrick McHardy a écrit : > commit 2eff25c18c3d332d3c4dd98f2ac9b7114e9771b0 > Author: Patrick McHardy <kaber@xxxxxxxxx> > Date: Wed Feb 3 13:24:54 2010 +0100 > > netfilter: xt_hashlimit: fix race condition and simplify locking > > As noticed by Shin Hong <hongshin@xxxxxxxxx>, there is a race between > htable_find_get() and htable_put(): > > htable_put(): htable_find_get(): > > spin_lock_bh(&hashlimit_lock); > <search entry> > atomic_dec_and_test(&hinfo->use) > atomic_inc(&hinfo->use) > spin_unlock_bh(&hashlimit_lock) > return hinfo; > spin_lock_bh(&hashlimit_lock); > hlist_del(&hinfo->node); > spin_unlock_bh(&hashlimit_lock); > htable_destroy(hinfo); > > The entire locking concept is overly complicated, tables are only > created/referenced and released in process context, so a single > mutex works just fine. Remove the hashinfo_spinlock and atomic > reference count and use the mutex to protect table lookups/creation > and reference count changes. > > Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx> > Patrick, David I believe this patch has a problem, since latest net-next-2.6 triggers : [ 240.682047] INFO: task iptables:4512 blocked for more than 120 seconds. [ 240.682125] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 240.682198] iptables D f7a69c48 0 4512 4436 0x00000000 [ 240.682201] f7a69c5c 00000086 00000002 f7a69c48 c3603304 00000000 c0379b0d 0000000e [ 240.682540] 00000138 f8c06504 fffbef49 d15abc2a 00000007 c0785000 c0788304 00000000 [ 240.682861] f81af0c0 c078d080 d157e120 00000007 f81aee40 c037a608 00000202 f9e38478 [ 240.683191] Call Trace: [ 240.683247] [<c0379b0d>] ? get_from_free_list+0x3d/0x50 [ 240.683303] [<c037a608>] ? ida_pre_get+0x18/0xe0 [ 240.683359] [<c05503ed>] __mutex_lock_slowpath+0xed/0x230 [ 240.683426] [<c0550540>] mutex_lock+0x10/0x20 [ 240.683488] [<c04dee7e>] hashlimit_mt_check+0x29e/0x380 [ 240.683544] [<c04de02c>] xt_check_match+0x9c/0x1b0 [ 240.683599] [<c05509a7>] ? __mutex_lock_interruptible_slowpath +0x1a7/0x260 [ 240.683657] [<c05509a7>] ? __mutex_lock_interruptible_slowpath +0x1a7/0x260 [ 240.683716] [<c05502fd>] ? mutex_unlock+0xd/0x10 [ 240.683770] [<c04ddb1f>] ? xt_find_match+0xdf/0x150 [ 240.683831] [<c0521994>] translate_table+0x384/0x760 [ 240.683886] [<c04dde02>] ? xt_alloc_table_info+0x52/0xc0 [ 240.683942] [<c0522bef>] do_ipt_set_ctl+0x16f/0x440 [ 240.683998] [<c04da2cb>] nf_sockopt+0x15b/0x1a0 [ 240.684062] [<c0551ca0>] ? _raw_spin_lock_bh+0x10/0x30 [ 240.684118] [<c04da369>] nf_setsockopt+0x29/0x30 [ 240.684177] [<c04eb96e>] ip_setsockopt+0x8e/0xa0 [ 240.684233] [<c02bd6ec>] ? page_add_new_anon_rmap+0x7c/0x90 [ 240.684289] [<c0504df4>] raw_setsockopt+0x44/0x80 [ 240.684345] [<c04aaf87>] sock_common_setsockopt+0x27/0x30 [ 240.684411] [<c04a9569>] sys_setsockopt+0x59/0xb0 [ 240.684472] [<c04aa90a>] sys_socketcall+0x12a/0x280 [ 240.684528] [<c0202c50>] sysenter_do_call+0x12/0x26 htable_create() is called with hashlimit_mutex already hold Maybe original race could be solved using atomic_inc_not_zero() instead of atomic_inc() ? Or following quick & dirty patch just cures the problem. Thanks [PATCH net-next-2.6] xt_hashlimit: fix locking Commit 2eff25c18c3d332d3c4dd98f2ac9b7114e9771b0 (netfilter: xt_hashlimit: fix race condition and simplify locking) added a mutex deadlock : htable_create() is called with hashlimit_mutex already locked Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx> diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c index e47fb80..d952806 100644 --- a/net/netfilter/xt_hashlimit.c +++ b/net/netfilter/xt_hashlimit.c @@ -262,9 +262,7 @@ static int htable_create_v0(struct net *net, struct xt_hashlimit_info *minfo, u_ hinfo->timer.expires = jiffies + msecs_to_jiffies(hinfo->cfg.gc_interval); add_timer(&hinfo->timer); - mutex_lock(&hashlimit_mutex); hlist_add_head(&hinfo->node, &hashlimit_net->htables); - mutex_unlock(&hashlimit_mutex); return 0; } @@ -327,9 +325,7 @@ static int htable_create(struct net *net, struct xt_hashlimit_mtinfo1 *minfo, hinfo->timer.expires = jiffies + msecs_to_jiffies(hinfo->cfg.gc_interval); add_timer(&hinfo->timer); - mutex_lock(&hashlimit_mutex); hlist_add_head(&hinfo->node, &hashlimit_net->htables); - mutex_unlock(&hashlimit_mutex); return 0; } -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
