6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit b5590270068c4324dac4a2b5a4a156e02e21339f ]
__netlink_dump_start() releases nlk->cb_mutex right before
calling netlink_dump() which grabs it again.
This seems dangerous, even if KASAN did not bother yet.
Add a @lock_taken parameter to netlink_dump() to let it
grab the mutex if called from netlink_recvmsg() only.
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/netlink/af_netlink.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 6ae782efb1ee3..db49fc4d42cf7 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -130,7 +130,7 @@ static const char *const nlk_cb_mutex_key_strings[MAX_LINKS + 1] = {
"nlk_cb_mutex-MAX_LINKS"
};
-static int netlink_dump(struct sock *sk);
+static int netlink_dump(struct sock *sk, bool lock_taken);
/* nl_table locking explained:
* Lookup and traversal are protected with an RCU read-side lock. Insertion
@@ -1989,7 +1989,7 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
if (READ_ONCE(nlk->cb_running) &&
atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) {
- ret = netlink_dump(sk);
+ ret = netlink_dump(sk, false);
if (ret) {
WRITE_ONCE(sk->sk_err, -ret);
sk_error_report(sk);
@@ -2198,7 +2198,7 @@ static int netlink_dump_done(struct netlink_sock *nlk, struct sk_buff *skb,
return 0;
}
-static int netlink_dump(struct sock *sk)
+static int netlink_dump(struct sock *sk, bool lock_taken)
{
struct netlink_sock *nlk = nlk_sk(sk);
struct netlink_ext_ack extack = {};
@@ -2210,7 +2210,8 @@ static int netlink_dump(struct sock *sk)
int alloc_min_size;
int alloc_size;
- mutex_lock(nlk->cb_mutex);
+ if (!lock_taken)
+ mutex_lock(nlk->cb_mutex);
if (!nlk->cb_running) {
err = -EINVAL;
goto errout_skb;
@@ -2367,9 +2368,7 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
WRITE_ONCE(nlk->cb_running, true);
nlk->dump_done_errno = INT_MAX;
- mutex_unlock(nlk->cb_mutex);
-
- ret = netlink_dump(sk);
+ ret = netlink_dump(sk, true);
sock_put(sk);
--
2.43.0
