Commit 7f5611cb authored by Matthieu Baerts (NGI0)'s avatar Matthieu Baerts (NGI0) Committed by Jakub Kicinski
Browse files

rds: sysctl: rds_tcp_{rcv,snd}buf: avoid using current->nsproxy 

As mentioned in a previous commit of this series, using the 'net'
structure via 'current' is not recommended for different reasons:

- Inconsistency: getting info from the reader's/writer's netns vs only
  from the opener's netns.

- current->nsproxy can be NULL in some cases, resulting in an 'Oops'
  (null-ptr-deref), e.g. when the current task is exiting, as spotted by
  syzbot [1] using acct(2).

The per-netns structure can be obtained from the table->data using
container_of(), then the 'net' one can be retrieved from the listen
socket (if available).

Fixes: c6a58ffe ("RDS: TCP: Add sysctl tunables for sndbuf/rcvbuf on rds-tcp socket")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/67769ecb.050a0220.3a8527.003f.GAE@google.com

 [1]
Suggested-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarMatthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-9-5df34b2083e8@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 6259d248

net/rds/tcp.c

+32 −7
Original line number Diff line number Diff line
@@ -61,7 +61,9 @@ static atomic_t rds_tcp_unloading = ATOMIC_INIT(0); 


static struct kmem_cache *rds_tcp_conn_slab;



static int rds_tcp_skbuf_handler(const struct ctl_table *ctl, int write,

static int rds_tcp_sndbuf_handler(const struct ctl_table *ctl, int write,

				  void *buffer, size_t *lenp, loff_t *fpos);

static int rds_tcp_rcvbuf_handler(const struct ctl_table *ctl, int write,

				  void *buffer, size_t *lenp, loff_t *fpos);



static int rds_tcp_min_sndbuf = SOCK_MIN_SNDBUF;
@@ -74,7 +76,7 @@ static struct ctl_table rds_tcp_sysctl_table[] = { 
		/* data is per-net pointer */

		.maxlen         = sizeof(int),

		.mode           = 0644,

		.proc_handler   = rds_tcp_skbuf_handler,

		.proc_handler   = rds_tcp_sndbuf_handler,

		.extra1		= &rds_tcp_min_sndbuf,

	},

#define	RDS_TCP_RCVBUF	1
@@ -83,7 +85,7 @@ static struct ctl_table rds_tcp_sysctl_table[] = { 
		/* data is per-net pointer */

		.maxlen         = sizeof(int),

		.mode           = 0644,

		.proc_handler   = rds_tcp_skbuf_handler,

		.proc_handler   = rds_tcp_rcvbuf_handler,

		.extra1		= &rds_tcp_min_rcvbuf,

	},

};
@@ -682,10 +684,10 @@ static void rds_tcp_sysctl_reset(struct net *net) 
	spin_unlock_irq(&rds_tcp_conn_lock);

}



static int rds_tcp_skbuf_handler(const struct ctl_table *ctl, int write,

static int rds_tcp_skbuf_handler(struct rds_tcp_net *rtn,

				 const struct ctl_table *ctl, int write,

				 void *buffer, size_t *lenp, loff_t *fpos)

{

	struct net *net = current->nsproxy->net_ns;

	int err;



	err = proc_dointvec_minmax(ctl, write, buffer, lenp, fpos);
@@ -694,11 +696,34 @@ static int rds_tcp_skbuf_handler(const struct ctl_table *ctl, int write, 
			*(int *)(ctl->extra1));

		return err;

	}

	if (write)



	if (write && rtn->rds_tcp_listen_sock && rtn->rds_tcp_listen_sock->sk) {

		struct net *net = sock_net(rtn->rds_tcp_listen_sock->sk);



		rds_tcp_sysctl_reset(net);

	}



	return 0;

}



static int rds_tcp_sndbuf_handler(const struct ctl_table *ctl, int write,

				  void *buffer, size_t *lenp, loff_t *fpos)

{

	struct rds_tcp_net *rtn = container_of(ctl->data, struct rds_tcp_net,

					       sndbuf_size);



	return rds_tcp_skbuf_handler(rtn, ctl, write, buffer, lenp, fpos);

}



static int rds_tcp_rcvbuf_handler(const struct ctl_table *ctl, int write,

				  void *buffer, size_t *lenp, loff_t *fpos)

{

	struct rds_tcp_net *rtn = container_of(ctl->data, struct rds_tcp_net,

					       rcvbuf_size);



	return rds_tcp_skbuf_handler(rtn, ctl, write, buffer, lenp, fpos);

}



static void rds_tcp_exit(void)

{

	rds_tcp_set_unloading();