From c0a767d6c7ecadaa8c89ff73b588a0e5a5714dc4 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Mon, 13 Jan 2020 18:09:58 +0100 Subject: [PATCH] netfilter: nf_tables: store transaction list locally while requesting module This patch fixes a WARN_ON in nft_set_destroy() due to missing set reference count drop from the preparation phase. This is triggered by the module autoload path. Do not exercise the abort path from nft_request_module() while preparation phase cleaning up is still pending. WARNING: CPU: 3 PID: 3456 at net/netfilter/nf_tables_api.c:3740 nft_set_destroy+0x45/0x50 [nf_tables] [...] CPU: 3 PID: 3456 Comm: nft Not tainted 5.4.6-arch3-1 #1 RIP: 0010:nft_set_destroy+0x45/0x50 [nf_tables] Code: e8 30 eb 83 c6 48 8b 85 80 00 00 00 48 8b b8 90 00 00 00 e8 dd 6b d7 c5 48 8b 7d 30 e8 24 dd eb c5 48 89 ef 5d e9 6b c6 e5 c5 <0f> 0b c3 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 8b 7f 10 e9 52 RSP: 0018:ffffac4f43e53700 EFLAGS: 00010202 RAX: 0000000000000001 RBX: ffff99d63a154d80 RCX: 0000000001f88e03 RDX: 0000000001f88c03 RSI: ffff99d6560ef0c0 RDI: ffff99d63a101200 RBP: ffff99d617721de0 R08: 0000000000000000 R09: 0000000000000318 R10: 00000000f0000000 R11: 0000000000000001 R12: ffffffff880fabf0 R13: dead000000000122 R14: dead000000000100 R15: ffff99d63a154d80 FS: 00007ff3dbd5b740(0000) GS:ffff99d6560c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00001cb5de6a9000 CR3: 000000016eb6a004 CR4: 00000000001606e0 Call Trace: __nf_tables_abort+0x3e3/0x6d0 [nf_tables] nft_request_module+0x6f/0x110 [nf_tables] nft_expr_type_request_module+0x28/0x50 [nf_tables] nf_tables_expr_parse+0x198/0x1f0 [nf_tables] nft_expr_init+0x3b/0xf0 [nf_tables] nft_dynset_init+0x1e2/0x410 [nf_tables] nf_tables_newrule+0x30a/0x930 [nf_tables] nfnetlink_rcv_batch+0x2a0/0x640 [nfnetlink] nfnetlink_rcv+0x125/0x171 [nfnetlink] netlink_unicast+0x179/0x210 netlink_sendmsg+0x208/0x3d0 sock_sendmsg+0x5e/0x60 ____sys_sendmsg+0x21b/0x290 Update comment on the code to describe the new behaviour. Reported-by: Marco Oliverio Fixes: 997096b81973 ("netfilter: nf_tables: add and use helper for module autoload") Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_tables_api.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 43f05b3acd600..168765d1d1c2b 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -564,23 +564,21 @@ __nf_tables_chain_type_lookup(const struct nlattr *nla, u8 family) } /* - * Loading a module requires dropping mutex that guards the - * transaction. - * We first need to abort any pending transactions as once - * mutex is unlocked a different client could start a new - * transaction. It must not see any 'future generation' - * changes * as these changes will never happen. + * Loading a module requires dropping mutex that guards the transaction. + * A different client might race to start a new transaction meanwhile. Zap the + * list of pending transaction and then restore it once the mutex is grabbed + * again. Users of this function return EAGAIN which implicitly triggers the + * transaction abort path to clean up the list of pending transactions. */ #ifdef CONFIG_MODULES -static int __nf_tables_abort(struct net *net); - static void nft_request_module(struct net *net, const char *fmt, ...) { char module_name[MODULE_NAME_LEN]; + LIST_HEAD(commit_list); va_list args; int ret; - __nf_tables_abort(net); + list_splice_init(&net->nft.commit_list, &commit_list); va_start(args, fmt); ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args); @@ -591,6 +589,9 @@ static void nft_request_module(struct net *net, const char *fmt, ...) mutex_unlock(&net->nft.commit_mutex); request_module("%s", module_name); mutex_lock(&net->nft.commit_mutex); + + WARN_ON_ONCE(!list_empty(&net->nft.commit_list)); + list_splice(&commit_list, &net->nft.commit_list); } #endif -- 2.39.5