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netlink: hold nlk->cb_mutex longer in __netlink_dump_start()

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__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@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2024-02-22 10:50:13 +00:00 committed by David S. Miller
parent 6647b338fc
commit b559027006
1 changed files with 6 additions and 7 deletions
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13
net/netlink/af_netlink.c
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@ -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
@ -1987,7 +1987,7 @@ 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);
@ -2196,7 +2196,7 @@ 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 = {};
@ -2208,7 +2208,8 @@ 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;
@ -2365,9 +2366,7 @@ 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);