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

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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: c6a58ffed5 ("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: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-9-5df34b2083e8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Matthieu Baerts (NGI0) 2025-01-08 16:34:37 +01:00 committed by Jakub Kicinski
parent 6259d2484d
commit 7f5611cbc4
1 changed files with 32 additions and 7 deletions
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39
net/rds/tcp.c
View file

@ -61,8 +61,10 @@ 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,
void *buffer, size_t *lenp, loff_t *fpos);
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;
static int rds_tcp_min_rcvbuf = SOCK_MIN_RCVBUF;
@ -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();