linux-kernel - Re: [PATCH v2] net: rds: fix memory leak in rds

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Message-ID: <3DEDB1BE-C48D-4B64-AB4B-B9C6D9505FC4@oracle.com>
Date:   Tue, 8 Jun 2021 12:29:56 +0000
From:   Haakon Bugge <haakon.bugge@...cle.com>
To:     Pavel Skripkin <paskripkin@...il.com>
CC:     Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        OFED mailing list <linux-rdma@...r.kernel.org>,
        "rds-devel@....oracle.com" <rds-devel@....oracle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "syzbot+5134cdf021c4ed5aaa5f@...kaller.appspotmail.com" 
        <syzbot+5134cdf021c4ed5aaa5f@...kaller.appspotmail.com>
Subject: Re: [PATCH v2] net: rds: fix memory leak in rds_recvmsg



> On 8 Jun 2021, at 10:06, Pavel Skripkin <paskripkin@...il.com> 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@...kaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin@...il.com>

Reviewed-by: Håkon Bugge <haakon.bugge@...cle.com>


Thanks for fixing this, Håkon

> ---
> 
> 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
>