5.10-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ 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@google.com Reviewed-by: Jiri Pirko jiri@nvidia.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- 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 ac3678d2d6d52..4f2a3d46554ff 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -126,7 +126,7 @@ 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 @@ -1996,7 +1996,7 @@ 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) { sk->sk_err = -ret; sk->sk_error_report(sk); @@ -2206,7 +2206,7 @@ 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 = {}; @@ -2218,7 +2218,8 @@ 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; @@ -2374,9 +2375,7 @@ 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);