From ab6c41eefd46b92e4f5bcdbbc6c1ea39ed148274 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 2 Oct 2020 13:51:29 +0200 Subject: [PATCH] netfilter: nfnetlink: place subsys mutexes in distinct lockdep classes From time to time there are lockdep reports similar to this one: WARNING: possible circular locking dependency detected ------------------------------------------------------ 000000004f61aa56 (&table[i].mutex){+.+.}, at: nfnl_lock [nfnetlink] but task is already holding lock: [..] (&net->nft.commit_mutex){+.+.}, at: nf_tables_valid_genid [nf_tables] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&net->nft.commit_mutex){+.+.}: [..] nf_tables_valid_genid+0x18/0x60 [nf_tables] nfnetlink_rcv_batch+0x24c/0x620 [nfnetlink] nfnetlink_rcv+0x110/0x140 [nfnetlink] netlink_unicast+0x12c/0x1e0 [..] sys_sendmsg+0x18/0x40 linux_sparc_syscall+0x34/0x44 -> #0 (&table[i].mutex){+.+.}: [..] nfnl_lock+0x24/0x40 [nfnetlink] ip_set_nfnl_get_byindex+0x19c/0x280 [ip_set] set_match_v1_checkentry+0x14/0xc0 [xt_set] xt_check_match+0x238/0x260 [x_tables] __nft_match_init+0x160/0x180 [nft_compat] [..] sys_sendmsg+0x18/0x40 linux_sparc_syscall+0x34/0x44 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&net->nft.commit_mutex); lock(&table[i].mutex); lock(&net->nft.commit_mutex); lock(&table[i].mutex); Lockdep considers this an ABBA deadlock because the different nfnl subsys mutexes reside in the same lockdep class, but this is a false positive. CPU1 table[i] refers to the nftables subsys mutex, whereas CPU1 locks the ipset subsys mutex. Yi Che reported a similar lockdep splat, this time between ipset and ctnetlink subsys mutexes. Time to place them in distinct classes to avoid these warnings. Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nfnetlink.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c index 3a2e64e13b22..2daa1f6ae344 100644 --- a/net/netfilter/nfnetlink.c +++ b/net/netfilter/nfnetlink.c @@ -46,6 +46,23 @@ static struct { const struct nfnetlink_subsystem __rcu *subsys; } table[NFNL_SUBSYS_COUNT]; +static struct lock_class_key nfnl_lockdep_keys[NFNL_SUBSYS_COUNT]; + +static const char *const nfnl_lockdep_names[NFNL_SUBSYS_COUNT] = { + [NFNL_SUBSYS_NONE] = "nfnl_subsys_none", + [NFNL_SUBSYS_CTNETLINK] = "nfnl_subsys_ctnetlink", + [NFNL_SUBSYS_CTNETLINK_EXP] = "nfnl_subsys_ctnetlink_exp", + [NFNL_SUBSYS_QUEUE] = "nfnl_subsys_queue", + [NFNL_SUBSYS_ULOG] = "nfnl_subsys_ulog", + [NFNL_SUBSYS_OSF] = "nfnl_subsys_osf", + [NFNL_SUBSYS_IPSET] = "nfnl_subsys_ipset", + [NFNL_SUBSYS_ACCT] = "nfnl_subsys_acct", + [NFNL_SUBSYS_CTNETLINK_TIMEOUT] = "nfnl_subsys_cttimeout", + [NFNL_SUBSYS_CTHELPER] = "nfnl_subsys_cthelper", + [NFNL_SUBSYS_NFTABLES] = "nfnl_subsys_nftables", + [NFNL_SUBSYS_NFT_COMPAT] = "nfnl_subsys_nftcompat", +}; + static const int nfnl_group2type[NFNLGRP_MAX+1] = { [NFNLGRP_CONNTRACK_NEW] = NFNL_SUBSYS_CTNETLINK, [NFNLGRP_CONNTRACK_UPDATE] = NFNL_SUBSYS_CTNETLINK, @@ -632,7 +649,7 @@ static int __init nfnetlink_init(void) BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE); for (i=0; i