[PATCH 4.19 21/48] ipv4: Fix data-races around sysctl_ip_dynaddr.

Greg Kroah-Hartman
2022-07-19T12:06:24Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit e49e4aff7ec19b2d0d0957ee30e93dade57dab9e ]

While reading sysctl_ip_dynaddr, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
Documentation/networking/ip-sysctl.txt | 2 +-
net/ipv4/af_inet.c | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index ae56957f51e4..e315e6052b9f 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -887,7 +887,7 @@ ip_nonlocal_bind - BOOLEAN
which can be quite useful - but may break some applications.
Default: 0

-ip_dynaddr - BOOLEAN
+ip_dynaddr - INTEGER
If set non-zero, enables support for dynamic addresses.
If set to a non-zero value larger than 1, a kernel log
message will be printed when dynamic address rewriting
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index d8c22246629a..dadd42a07c07 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1209,7 +1209,7 @@ static int inet_sk_reselect_saddr(struct sock *sk)
if (new_saddr == old_saddr)
return 0;

- if (sock_net(sk)->ipv4.sysctl_ip_dynaddr > 1) {
+ if (READ_ONCE(sock_net(sk)->ipv4.sysctl_ip_dynaddr) > 1) {
pr_info("%s(): shifting inet->saddr from %pI4 to %pI4\n",
__func__, &old_saddr, &new_saddr);
}
@@ -1264,7 +1264,7 @@ int inet_sk_rebuild_header(struct sock *sk)
* Other protocols have to map its equivalent state to TCP_SYN_SENT.
* DCCP maps its DCCP_REQUESTING state to TCP_SYN_SENT. -acme
*/
- if (!sock_net(sk)->ipv4.sysctl_ip_dynaddr ||
+ if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_ip_dynaddr) ||
sk->sk_state != TCP_SYN_SENT ||
(sk->sk_userlocks & SOCK_BINDADDR_LOCK) ||
(err = inet_sk_reselect_saddr(sk)) != 0)
--
2.35.1