[PATCH 4.19 063/103] netfilter: nf_tables: store transaction list locally while requesting module

Greg Kroah-Hartman
2020-01-22T09:46:10Z

From: Pablo Neira Ayuso <pablo@netfilter.org>

commit ec7470b834fe7b5d7eff11b6677f5d7fdf5e9a91 upstream.

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 <marco.oliverio@tanaza.com>
Fixes: 452238e8d5ff ("netfilter: nf_tables: add and use helper for module autoload")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/netfilter/nf_tables_api.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -485,23 +485,21 @@ __nf_tables_chain_type_lookup(const stru
}

/*
- * 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);
@@ -512,6 +510,9 @@ static void nft_request_module(struct ne
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