[PATCH net] Revert "Revert "ipv4: fix memory leaks in ip_cmsg_send() callers""

From: Eric Dumazet <edumazet@google.com>

This reverts commit d7807a9adf4856171f8441f13078c33941df48ab.

As mentioned in https://lkml.org/lkml/2021/9/13/1819
5 years old commit 919483096bfe ("ipv4: fix memory leaks in ip_cmsg_send() callers")
was a correct fix.

  ip_cmsg_send() can loop over multiple cmsghdr()

  If IP_RETOPTS has been successful, but following cmsghdr generates an error,
  we do not free ipc.ok

  If IP_RETOPTS is not successful, we have freed the allocated temporary space,
  not the one currently in ipc.opt.

Sure, code could be refactored, but let's not bring back old bugs.

Fixes: d7807a9adf48 ("Revert "ipv4: fix memory leaks in ip_cmsg_send() callers"")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yajun Deng <redacted>
---
 net/ipv4/ip_sockglue.c | 2 +-
 net/ipv4/ping.c        | 5 +++--
 net/ipv4/raw.c         | 5 +++--
 net/ipv4/udp.c         | 5 +++--
 4 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 7cef9987ab4ace4444c4b470a3393ce50219a69a..b297bb28556ec5cf383068f67ee910af38591cc3 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c

@@ -279,7 +279,7 @@ int ip_cmsg_send(struct sock *sk, struct msghdr *msg, struct ipcm_cookie *ipc,
 		case IP_RETOPTS:
 			err = cmsg->cmsg_len - sizeof(struct cmsghdr);
 
-			/* Our caller is responsible for freeing ipc->opt when err = 0 */
+			/* Our caller is responsible for freeing ipc->opt */
 			err = ip_options_get(net, &ipc->opt,
 					     KERNEL_SOCKPTR(CMSG_DATA(cmsg)),
 					     err < 40 ? err : 40);

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index c588f9f2f46c2b91fc9424ecfc0590b2b63a3470..1e44a43acfe2dfe57efdc64479c2d18402881d73 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c

@@ -727,9 +727,10 @@ static int ping_v4_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
 	if (msg->msg_controllen) {
 		err = ip_cmsg_send(sk, msg, &ipc, false);
-		if (unlikely(err))
+		if (unlikely(err)) {
+			kfree(ipc.opt);
 			return err;
-
+		}
 		if (ipc.opt)
 			free = 1;
 	}

diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index 1c98063a3ae816ecfd7135b0168fea5a9380676f..bb446e60cf58057b448f094b4d6f48d6e91d113c 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c

@@ -562,9 +562,10 @@ static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
 	if (msg->msg_controllen) {
 		err = ip_cmsg_send(sk, msg, &ipc, false);
-		if (unlikely(err))
+		if (unlikely(err)) {
+			kfree(ipc.opt);
 			goto out;
-
+		}
 		if (ipc.opt)
 			free = 1;
 	}

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index d5f5981d7a43244cace63653b790a34174364e3e..8851c9463b4b62c9017565f545250c4ffe22927c 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c

@@ -1122,9 +1122,10 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		if (err > 0)
 			err = ip_cmsg_send(sk, msg, &ipc,
 					   sk->sk_family == AF_INET6);
-		if (unlikely(err < 0))
+		if (unlikely(err < 0)) {
+			kfree(ipc.opt);
 			return err;
-
+		}
 		if (ipc.opt)
 			free = 1;
 		connected = 0;

-- 
2.33.0.309.g3052b89438-goog

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Mon, 13 Sep 2021 22:18:51 -0700 you wrote:

From: Eric Dumazet <edumazet@google.com>

This reverts commit d7807a9adf4856171f8441f13078c33941df48ab.

As mentioned in https://lkml.org/lkml/2021/9/13/1819
5 years old commit 919483096bfe ("ipv4: fix memory leaks in ip_cmsg_send() callers")
was a correct fix.

[...]

Here is the summary with links:
  - [net] Revert "Revert "ipv4: fix memory leaks in ip_cmsg_send() callers""
    https://git.kernel.org/netdev/net/c/d198b2776264

You are awesome, thank you!
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