[PATCH] net: rds: fix memory leak in rds_recvmsg

Syzbot reported memory leak in rds. The problem
was in unputted refcount in case of error.

int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
		int msg_flags)
{
...

	if (!rds_next_incoming(rs, &inc)) {
		...
	}

After this "if" inc refcount incremented and

	if (rds_cmsg_recv(inc, msg, rs)) {
		ret = -EFAULT;
		goto out;
	}
...
out:
	return ret;
}

in case of rds_cmsg_recv() fail the refcount won't be
decremented. And it's easy to see from ftrace log, that
rds_inc_addref() don't have rds_inc_put() pair in
rds_recvmsg() after rds_cmsg_recv()

 1)               |  rds_recvmsg() {
 1)   3.721 us    |    rds_inc_addref();
 1)   3.853 us    |    rds_message_inc_copy_to_user();
 1) + 10.395 us   |    rds_cmsg_recv();
 1) + 34.260 us   |  }

Fixes: bdbe6fbc6a2f ("RDS: recv.c")
Reported-and-tested-by: syzbot+5134cdf021c4ed5aaa5f@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <redacted>
---
 net/rds/recv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/rds/recv.c b/net/rds/recv.c
index 4db109fb6ec2..3fa16c339bfe 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c

@@ -714,7 +714,7 @@ int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
 
 		if (rds_cmsg_recv(inc, msg, rs)) {
 			ret = -EFAULT;
-			goto out;
+			goto out_put;
 		}
 		rds_recvmsg_zcookie(rs, msg);
 

@@ -740,6 +740,7 @@ int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
 		break;
 	}
 
+out_put:
 	if (inc)
 		rds_inc_put(inc);
 

-- 
2.31.1

On 7 Jun 2021, at 21:41, Pavel Skripkin [off-list ref] wrote:

Syzbot reported memory leak in rds. The problem
was in unputted refcount in case of error.

int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
		int msg_flags)
{
...

	if (!rds_next_incoming(rs, &inc)) {
		...
	}

After this "if" inc refcount incremented and

	if (rds_cmsg_recv(inc, msg, rs)) {
		ret = -EFAULT;
		goto out;
	}
...
out:
	return ret;
}

in case of rds_cmsg_recv() fail the refcount won't be
decremented. And it's easy to see from ftrace log, that
rds_inc_addref() don't have rds_inc_put() pair in
rds_recvmsg() after rds_cmsg_recv()

1)               |  rds_recvmsg() {
1)   3.721 us    |    rds_inc_addref();
1)   3.853 us    |    rds_message_inc_copy_to_user();
1) + 10.395 us   |    rds_cmsg_recv();
1) + 34.260 us   |  }

Fixes: bdbe6fbc6a2f ("RDS: recv.c")
Reported-and-tested-by: syzbot+5134cdf021c4ed5aaa5f@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <redacted>

Thank for your commit and analyses. One small nit below.

Would a simple "break;" do it here and no need for the next hunk?


Thxs, Håkon

On Tue, 8 Jun 2021 07:11:27 +0000
Haakon Bugge [off-list ref] wrote:

quoted

On 7 Jun 2021, at 21:41, Pavel Skripkin [off-list ref]
wrote:

Syzbot reported memory leak in rds. The problem
was in unputted refcount in case of error.

int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t
size, int msg_flags)
{
...

	if (!rds_next_incoming(rs, &inc)) {
		...
	}

After this "if" inc refcount incremented and

	if (rds_cmsg_recv(inc, msg, rs)) {
		ret = -EFAULT;
		goto out;
	}
...
out:
	return ret;
}

in case of rds_cmsg_recv() fail the refcount won't be
decremented. And it's easy to see from ftrace log, that
rds_inc_addref() don't have rds_inc_put() pair in
rds_recvmsg() after rds_cmsg_recv()

1)               |  rds_recvmsg() {
1)   3.721 us    |    rds_inc_addref();
1)   3.853 us    |    rds_message_inc_copy_to_user();
1) + 10.395 us   |    rds_cmsg_recv();
1) + 34.260 us   |  }

Fixes: bdbe6fbc6a2f ("RDS: recv.c")
Reported-and-tested-by:
syzbot+5134cdf021c4ed5aaa5f@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <redacted>

Thank for your commit and analyses. One small nit below.

quoted

---
net/rds/recv.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/rds/recv.c b/net/rds/recv.c
index 4db109fb6ec2..3fa16c339bfe 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c

@@ -714,7 +714,7 @@ int rds_recvmsg(struct socket *sock, struct

msghdr *msg, size_t size,

		if (rds_cmsg_recv(inc, msg, rs)) {
			ret = -EFAULT;
-			goto out;
+			goto out_put;

Would a simple "break;" do it here and no need for the next hunk?


Thxs, Håkon

Sure! I'll send v2 soon. Thank you for feedback :)


With regards,
Pavel Skripkin

Syzbot reported memory leak in rds. The problem
was in unputted refcount in case of error.

int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
		int msg_flags)
{
...

	if (!rds_next_incoming(rs, &inc)) {
		...
	}

After this "if" inc refcount incremented and

	if (rds_cmsg_recv(inc, msg, rs)) {
		ret = -EFAULT;
		goto out;
	}
...
out:
	return ret;
}

in case of rds_cmsg_recv() fail the refcount won't be
decremented. And it's easy to see from ftrace log, that
rds_inc_addref() don't have rds_inc_put() pair in
rds_recvmsg() after rds_cmsg_recv()

 1)               |  rds_recvmsg() {
 1)   3.721 us    |    rds_inc_addref();
 1)   3.853 us    |    rds_message_inc_copy_to_user();
 1) + 10.395 us   |    rds_cmsg_recv();
 1) + 34.260 us   |  }

Fixes: bdbe6fbc6a2f ("RDS: recv.c")
Reported-and-tested-by: syzbot+5134cdf021c4ed5aaa5f@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <redacted>
---

Changes in v2:
	Changed goto to break.

---
 net/rds/recv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rds/recv.c b/net/rds/recv.c
index 4db109fb6ec2..5b426dc3634d 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c

@@ -714,7 +714,7 @@ int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
 
 		if (rds_cmsg_recv(inc, msg, rs)) {
 			ret = -EFAULT;
-			goto out;
+			break;
 		}
 		rds_recvmsg_zcookie(rs, msg);
 

-- 
2.31.1

On 8 Jun 2021, at 10:06, Pavel Skripkin [off-list ref] wrote:

Syzbot reported memory leak in rds. The problem
was in unputted refcount in case of error.

int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
		int msg_flags)
{
...

	if (!rds_next_incoming(rs, &inc)) {
		...
	}

After this "if" inc refcount incremented and

	if (rds_cmsg_recv(inc, msg, rs)) {
		ret = -EFAULT;
		goto out;
	}
...
out:
	return ret;
}

in case of rds_cmsg_recv() fail the refcount won't be
decremented. And it's easy to see from ftrace log, that
rds_inc_addref() don't have rds_inc_put() pair in
rds_recvmsg() after rds_cmsg_recv()

1)               |  rds_recvmsg() {
1)   3.721 us    |    rds_inc_addref();
1)   3.853 us    |    rds_message_inc_copy_to_user();
1) + 10.395 us   |    rds_cmsg_recv();
1) + 34.260 us   |  }

Fixes: bdbe6fbc6a2f ("RDS: recv.c")
Reported-and-tested-by: syzbot+5134cdf021c4ed5aaa5f@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <redacted>

Reviewed-by: Håkon Bugge <redacted>


Thanks for fixing this, Håkon

On Jun 8, 2021, at 1:06 AM, Pavel Skripkin [off-list ref] wrote:

Syzbot reported memory leak in rds. The problem
was in unputted refcount in case of error.

int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
		int msg_flags)
{
...

	if (!rds_next_incoming(rs, &inc)) {
		...
	}

After this "if" inc refcount incremented and

	if (rds_cmsg_recv(inc, msg, rs)) {
		ret = -EFAULT;
		goto out;
	}
...
out:
	return ret;
}

in case of rds_cmsg_recv() fail the refcount won't be
decremented. And it's easy to see from ftrace log, that
rds_inc_addref() don't have rds_inc_put() pair in
rds_recvmsg() after rds_cmsg_recv()

1)               |  rds_recvmsg() {
1)   3.721 us    |    rds_inc_addref();
1)   3.853 us    |    rds_message_inc_copy_to_user();
1) + 10.395 us   |    rds_cmsg_recv();
1) + 34.260 us   |  }

Fixes: bdbe6fbc6a2f ("RDS: recv.c")
Reported-and-tested-by: syzbot+5134cdf021c4ed5aaa5f@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <redacted>
---

Changes in v2:
	Changed goto to break.

Looks fine by me. Thanks for the fix.

Acked-by: Santosh Shilimkar <redacted>

Hello:

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

On Tue,  8 Jun 2021 11:06:41 +0300 you wrote:

Syzbot reported memory leak in rds. The problem
was in unputted refcount in case of error.

int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
		int msg_flags)
{
...

[...]

Here is the summary with links:
  - [v2] net: rds: fix memory leak in rds_recvmsg
    https://git.kernel.org/netdev/net/c/49bfcbfd989a

You are awesome, thank you!
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