From: Florian Westphal <f...@strlen.de>
modprobe calls from the nf_logger_find_get() API causes deadlock in very
special cases because they occur with the nf_tables transaction mutex held.
In the specific case of nf_log, deadlock is via:
A nf_tables -> transaction mutex -> nft_log -> modprobe -> nf_log_syslog \
-> pernet_ops rwsem -> wait for C
B netlink event -> rtnl_mutex -> nf_tables transaction mutex -> wait for A
C close() -> ip6mr_sk_done -> rtnl_mutex -> wait for B
Earlier patch added NFLOG/xt_LOG module softdeps to avoid the need to load
the backend module during a transaction.
For nft_log we would have to add a softdep for both nfnetlink_log or
nf_log_syslog, since we do not know in advance which of the two backends
are going to be configured.
This defers the modprobe op until after the transaction mutex is released.
Tested-by: Phil Sutter <p...@nwl.cc>
Signed-off-by: Florian Westphal <f...@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
---
include/net/netfilter/nf_tables.h | 5 +++++
net/netfilter/nf_log.c | 3 ---
net/netfilter/nf_tables_api.c | 5 +++--
net/netfilter/nft_log.c | 20 +++++++++++++++++++-
4 files changed, 27 insertions(+), 6 deletions(-)
diff --git a/include/net/netfilter/nf_tables.h
b/include/net/netfilter/nf_tables.h
index 0cef5ad9768a..8fefa112ae89 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -1562,4 +1562,9 @@ void nf_tables_trans_destroy_flush_work(void);
int nf_msecs_to_jiffies64(const struct nlattr *nla, u64 *result);
__be64 nf_jiffies64_to_msecs(u64 input);
+#ifdef CONFIG_MODULES
+__printf(2, 3) int nft_request_module(struct net *net, const char *fmt, ...);
+#else
+static inline int nft_request_module(struct net *net, const char *fmt, ...) {
return -ENOENT; }
+#endif
#endif /* _NET_NF_TABLES_H */
diff --git a/net/netfilter/nf_log.c b/net/netfilter/nf_log.c
index eaa8181f5ef7..edee7fa944c1 100644
--- a/net/netfilter/nf_log.c
+++ b/net/netfilter/nf_log.c
@@ -170,9 +170,6 @@ int nf_logger_find_get(int pf, enum nf_log_type type)
return 0;
}
- if (rcu_access_pointer(loggers[pf][type]) == NULL)
- request_module("nf-logger-%u-%u", pf, type);
-
rcu_read_lock();
logger = rcu_dereference(loggers[pf][type]);
if (logger == NULL)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index fc2526b8bd55..c09b67f2f64c 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -586,8 +586,8 @@ struct nft_module_request {
};
#ifdef CONFIG_MODULES
-static __printf(2, 3) int nft_request_module(struct net *net, const char *fmt,
- ...)
+__printf(2, 3) int nft_request_module(struct net *net, const char *fmt,
+ ...)
{
char module_name[MODULE_NAME_LEN];
struct nft_module_request *req;
@@ -620,6 +620,7 @@ static __printf(2, 3) int nft_request_module(struct net
*net, const char *fmt,
return -EAGAIN;
}
+EXPORT_SYMBOL_GPL(nft_request_module);
#endif
static void lockdep_nfnl_nft_mutex_not_held(void)
diff --git a/net/netfilter/nft_log.c b/net/netfilter/nft_log.c
index a06a46b039c5..54f6c2035e84 100644
--- a/net/netfilter/nft_log.c
+++ b/net/netfilter/nft_log.c
@@ -128,6 +128,20 @@ static const struct nla_policy nft_log_policy[NFTA_LOG_MAX
+ 1] = {
[NFTA_LOG_FLAGS] = { .type = NLA_U32 },
};
+static int nft_log_modprobe(struct net *net, enum nf_log_type t)
+{
+ switch (t) {
+ case NF_LOG_TYPE_LOG:
+ return nft_request_module(net, "%s", "nf_log_syslog");
+ case NF_LOG_TYPE_ULOG:
+ return nft_request_module(net, "%s", "nfnetlink_log");
+ case NF_LOG_TYPE_MAX:
+ break;
+ }
+
+ return -ENOENT;
+}
+
static int nft_log_init(const struct nft_ctx *ctx,
const struct nft_expr *expr,
const struct nlattr * const tb[])
@@ -197,8 +211,12 @@ static int nft_log_init(const struct nft_ctx *ctx,
return 0;
err = nf_logger_find_get(ctx->family, li->type);
- if (err < 0)
+ if (err < 0) {
+ if (nft_log_modprobe(ctx->net, li->type) == -EAGAIN)
+ err = -EAGAIN;
+
goto err1;
+ }
return 0;
--
2.30.2
