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

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

[Yajun Deng]

This reverts commit 919483096bfe75dda338e98d56da91a263746a0a.

There is only when ip_options_get() return zero need to free.
It already called kfree() when return error.

Fixes: 919483096bfe ("ipv4: fix memory leaks in ip_cmsg_send() callers")
Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
---
 net/ipv4/ip_sockglue.c | 2 +-
 net/ipv4/ping.c        | 5 ++---
 net/ipv4/raw.c         | 5 ++---
 net/ipv4/udp.c         | 5 ++---
 4 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index b297bb28556e..7cef9987ab4a 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 */
+			/* Our caller is responsible for freeing ipc->opt when err = 0 */
 			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 1e44a43acfe2..c588f9f2f46c 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -727,10 +727,9 @@ 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)) {
-			kfree(ipc.opt);
+		if (unlikely(err))
 			return err;
-		}
+
 		if (ipc.opt)
 			free = 1;
 	}
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index bb446e60cf58..1c98063a3ae8 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -562,10 +562,9 @@ 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)) {
-			kfree(ipc.opt);
+		if (unlikely(err))
 			goto out;
-		}
+
 		if (ipc.opt)
 			free = 1;
 	}
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 8851c9463b4b..d5f5981d7a43 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1122,10 +1122,9 @@ 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)) {
-			kfree(ipc.opt);
+		if (unlikely(err < 0))
 			return err;
-		}
+
 		if (ipc.opt)
 			free = 1;
 		connected = 0;
-- 
2.32.0

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

[patchwork-bot+netdevbpf]

Hello:

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

On Mon, 13 Sep 2021 12:04:42 +0800 you wrote:
> This reverts commit 919483096bfe75dda338e98d56da91a263746a0a.
> 
> There is only when ip_options_get() return zero need to free.
> It already called kfree() when return error.
> 
> Fixes: 919483096bfe ("ipv4: fix memory leaks in ip_cmsg_send() callers")
> Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
> 
> [...]

Here is the summary with links:
  - Revert "ipv4: fix memory leaks in ip_cmsg_send() callers"
    https://git.kernel.org/netdev/net/c/d7807a9adf48

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

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

[Eric Dumazet]

On Sun, Sep 12, 2021 at 9:04 PM Yajun Deng <yajun.deng@linux.dev> wrote:
>
> This reverts commit 919483096bfe75dda338e98d56da91a263746a0a.
>
> There is only when ip_options_get() return zero need to free.
> It already called kfree() when return error.
>
> Fixes: 919483096bfe ("ipv4: fix memory leaks in ip_cmsg_send() callers")
> Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
> ---

I do not think this is a valid patch, not sure why David has merged so
soon before us reviewing it ?

You are bringing back the memory leaks.

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.

Can you share what your exact finding was, perhaps a syzbot repro ???

Thanks.

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

[yajun.deng]

September 14, 2021 12:15 AM, "Eric Dumazet" <edumazet@google.com> wrote:

> On Sun, Sep 12, 2021 at 9:04 PM Yajun Deng <yajun.deng@linux.dev> wrote:
> 
>> This reverts commit 919483096bfe75dda338e98d56da91a263746a0a.
>> 
>> There is only when ip_options_get() return zero need to free.
>> It already called kfree() when return error.
>> 
>> Fixes: 919483096bfe ("ipv4: fix memory leaks in ip_cmsg_send() callers")
>> Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
>> ---
> 
> I do not think this is a valid patch, not sure why David has merged so
> soon before us reviewing it ?
> 
> You are bringing back the memory leaks.
> 
> ip_cmsg_send() can loop over multiple cmsghdr()
> 

Yes, I forgot the loop, it was my mistake.

> 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.
> 
> Can you share what your exact finding was, perhaps a syzbot repro ???
> 
> Thanks.