linux/drivers/infiniband/core/netlink.c
Parav Pandit 549af00833 IB/core: Avoid deadlock during netlink message handling
When rdmacm module is not loaded, and when netlink message is received to
get char device info, it results into a deadlock due to recursive locking
of rdma_nl_mutex with the below call sequence.

[..]
  rdma_nl_rcv()
  mutex_lock()
   [..]
   rdma_nl_rcv_msg()
      ib_get_client_nl_info()
         request_module()
           iw_cm_init()
             rdma_nl_register()
               mutex_lock(); <- Deadlock, acquiring mutex again

Due to above call sequence, following call trace and deadlock is observed.

  kernel: __mutex_lock+0x35e/0x860
  kernel: ? __mutex_lock+0x129/0x860
  kernel: ? rdma_nl_register+0x1a/0x90 [ib_core]
  kernel: rdma_nl_register+0x1a/0x90 [ib_core]
  kernel: ? 0xffffffffc029b000
  kernel: iw_cm_init+0x34/0x1000 [iw_cm]
  kernel: do_one_initcall+0x67/0x2d4
  kernel: ? kmem_cache_alloc_trace+0x1ec/0x2a0
  kernel: do_init_module+0x5a/0x223
  kernel: load_module+0x1998/0x1e10
  kernel: ? __symbol_put+0x60/0x60
  kernel: __do_sys_finit_module+0x94/0xe0
  kernel: do_syscall_64+0x5a/0x270
  kernel: entry_SYSCALL_64_after_hwframe+0x49/0xbe

  process stack trace:
  [<0>] __request_module+0x1c9/0x460
  [<0>] ib_get_client_nl_info+0x5e/0xb0 [ib_core]
  [<0>] nldev_get_chardev+0x1ac/0x320 [ib_core]
  [<0>] rdma_nl_rcv_msg+0xeb/0x1d0 [ib_core]
  [<0>] rdma_nl_rcv+0xcd/0x120 [ib_core]
  [<0>] netlink_unicast+0x179/0x220
  [<0>] netlink_sendmsg+0x2f6/0x3f0
  [<0>] sock_sendmsg+0x30/0x40
  [<0>] ___sys_sendmsg+0x27a/0x290
  [<0>] __sys_sendmsg+0x58/0xa0
  [<0>] do_syscall_64+0x5a/0x270
  [<0>] entry_SYSCALL_64_after_hwframe+0x49/0xbe

To overcome this deadlock and to allow multiple netlink messages to
progress in parallel, following scheme is implemented.

1. Split the lock protecting the cb_table into a per-index lock, and make
   it a rwlock. This lock is used to ensure no callbacks are running after
   unregistration returns. Since a module will not be registered once it
   is already running callbacks, this avoids the deadlock.

2. Use smp_store_release() to update the cb_table during registration so
   that no lock is required. This avoids lockdep problems with thinking
   all the rwsems are the same lock class.

Fixes: 0e2d00eb6f ("RDMA: Add NLDEV_GET_CHARDEV to allow char dev discovery and autoload")
Link: https://lore.kernel.org/r/20191015080733.18625-1-leon@kernel.org
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
2019-10-24 20:49:37 -03:00

332 lines
8.6 KiB
C

/*
* Copyright (c) 2017 Mellanox Technologies Inc. All rights reserved.
* Copyright (c) 2010 Voltaire Inc. All rights reserved.
*
* This software is available to you under a choice of one of two
* licenses. You may choose to be licensed under the terms of the GNU
* General Public License (GPL) Version 2, available from the file
* COPYING in the main directory of this source tree, or the
* OpenIB.org BSD license below:
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above
* copyright notice, this list of conditions and the following
* disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#define pr_fmt(fmt) "%s:%s: " fmt, KBUILD_MODNAME, __func__
#include <linux/export.h>
#include <net/netlink.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/sock.h>
#include <rdma/rdma_netlink.h>
#include <linux/module.h>
#include "core_priv.h"
static struct {
const struct rdma_nl_cbs *cb_table;
/* Synchronizes between ongoing netlink commands and netlink client
* unregistration.
*/
struct rw_semaphore sem;
} rdma_nl_types[RDMA_NL_NUM_CLIENTS];
bool rdma_nl_chk_listeners(unsigned int group)
{
struct rdma_dev_net *rnet = rdma_net_to_dev_net(&init_net);
return netlink_has_listeners(rnet->nl_sock, group);
}
EXPORT_SYMBOL(rdma_nl_chk_listeners);
static bool is_nl_msg_valid(unsigned int type, unsigned int op)
{
static const unsigned int max_num_ops[RDMA_NL_NUM_CLIENTS] = {
[RDMA_NL_IWCM] = RDMA_NL_IWPM_NUM_OPS,
[RDMA_NL_LS] = RDMA_NL_LS_NUM_OPS,
[RDMA_NL_NLDEV] = RDMA_NLDEV_NUM_OPS,
};
/*
* This BUILD_BUG_ON is intended to catch addition of new
* RDMA netlink protocol without updating the array above.
*/
BUILD_BUG_ON(RDMA_NL_NUM_CLIENTS != 6);
if (type >= RDMA_NL_NUM_CLIENTS)
return false;
return (op < max_num_ops[type]) ? true : false;
}
static const struct rdma_nl_cbs *
get_cb_table(const struct sk_buff *skb, unsigned int type, unsigned int op)
{
const struct rdma_nl_cbs *cb_table;
/*
* Currently only NLDEV client is supporting netlink commands in
* non init_net net namespace.
*/
if (sock_net(skb->sk) != &init_net && type != RDMA_NL_NLDEV)
return NULL;
cb_table = READ_ONCE(rdma_nl_types[type].cb_table);
if (!cb_table) {
/*
* Didn't get valid reference of the table, attempt module
* load once.
*/
up_read(&rdma_nl_types[type].sem);
request_module("rdma-netlink-subsys-%d", type);
down_read(&rdma_nl_types[type].sem);
cb_table = READ_ONCE(rdma_nl_types[type].cb_table);
}
if (!cb_table || (!cb_table[op].dump && !cb_table[op].doit))
return NULL;
return cb_table;
}
void rdma_nl_register(unsigned int index,
const struct rdma_nl_cbs cb_table[])
{
if (WARN_ON(!is_nl_msg_valid(index, 0)) ||
WARN_ON(READ_ONCE(rdma_nl_types[index].cb_table)))
return;
/* Pairs with the READ_ONCE in is_nl_valid() */
smp_store_release(&rdma_nl_types[index].cb_table, cb_table);
}
EXPORT_SYMBOL(rdma_nl_register);
void rdma_nl_unregister(unsigned int index)
{
down_write(&rdma_nl_types[index].sem);
rdma_nl_types[index].cb_table = NULL;
up_write(&rdma_nl_types[index].sem);
}
EXPORT_SYMBOL(rdma_nl_unregister);
void *ibnl_put_msg(struct sk_buff *skb, struct nlmsghdr **nlh, int seq,
int len, int client, int op, int flags)
{
*nlh = nlmsg_put(skb, 0, seq, RDMA_NL_GET_TYPE(client, op), len, flags);
if (!*nlh)
return NULL;
return nlmsg_data(*nlh);
}
EXPORT_SYMBOL(ibnl_put_msg);
int ibnl_put_attr(struct sk_buff *skb, struct nlmsghdr *nlh,
int len, void *data, int type)
{
if (nla_put(skb, type, len, data)) {
nlmsg_cancel(skb, nlh);
return -EMSGSIZE;
}
return 0;
}
EXPORT_SYMBOL(ibnl_put_attr);
static int rdma_nl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
struct netlink_ext_ack *extack)
{
int type = nlh->nlmsg_type;
unsigned int index = RDMA_NL_GET_CLIENT(type);
unsigned int op = RDMA_NL_GET_OP(type);
const struct rdma_nl_cbs *cb_table;
int err = -EINVAL;
if (!is_nl_msg_valid(index, op))
return -EINVAL;
down_read(&rdma_nl_types[index].sem);
cb_table = get_cb_table(skb, index, op);
if (!cb_table)
goto done;
if ((cb_table[op].flags & RDMA_NL_ADMIN_PERM) &&
!netlink_capable(skb, CAP_NET_ADMIN)) {
err = -EPERM;
goto done;
}
/*
* LS responses overload the 0x100 (NLM_F_ROOT) flag. Don't
* mistakenly call the .dump() function.
*/
if (index == RDMA_NL_LS) {
if (cb_table[op].doit)
err = cb_table[op].doit(skb, nlh, extack);
goto done;
}
/* FIXME: Convert IWCM to properly handle doit callbacks */
if ((nlh->nlmsg_flags & NLM_F_DUMP) || index == RDMA_NL_IWCM) {
struct netlink_dump_control c = {
.dump = cb_table[op].dump,
};
if (c.dump)
err = netlink_dump_start(skb->sk, skb, nlh, &c);
goto done;
}
if (cb_table[op].doit)
err = cb_table[op].doit(skb, nlh, extack);
done:
up_read(&rdma_nl_types[index].sem);
return err;
}
/*
* This function is similar to netlink_rcv_skb with one exception:
* It calls to the callback for the netlink messages without NLM_F_REQUEST
* flag. These messages are intended for RDMA_NL_LS consumer, so it is allowed
* for that consumer only.
*/
static int rdma_nl_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
struct nlmsghdr *,
struct netlink_ext_ack *))
{
struct netlink_ext_ack extack = {};
struct nlmsghdr *nlh;
int err;
while (skb->len >= nlmsg_total_size(0)) {
int msglen;
nlh = nlmsg_hdr(skb);
err = 0;
if (nlh->nlmsg_len < NLMSG_HDRLEN || skb->len < nlh->nlmsg_len)
return 0;
/*
* Generally speaking, the only requests are handled
* by the kernel, but RDMA_NL_LS is different, because it
* runs backward netlink scheme. Kernel initiates messages
* and waits for reply with data to keep pathrecord cache
* in sync.
*/
if (!(nlh->nlmsg_flags & NLM_F_REQUEST) &&
(RDMA_NL_GET_CLIENT(nlh->nlmsg_type) != RDMA_NL_LS))
goto ack;
/* Skip control messages */
if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
goto ack;
err = cb(skb, nlh, &extack);
if (err == -EINTR)
goto skip;
ack:
if (nlh->nlmsg_flags & NLM_F_ACK || err)
netlink_ack(skb, nlh, err, &extack);
skip:
msglen = NLMSG_ALIGN(nlh->nlmsg_len);
if (msglen > skb->len)
msglen = skb->len;
skb_pull(skb, msglen);
}
return 0;
}
static void rdma_nl_rcv(struct sk_buff *skb)
{
rdma_nl_rcv_skb(skb, &rdma_nl_rcv_msg);
}
int rdma_nl_unicast(struct net *net, struct sk_buff *skb, u32 pid)
{
struct rdma_dev_net *rnet = rdma_net_to_dev_net(net);
int err;
err = netlink_unicast(rnet->nl_sock, skb, pid, MSG_DONTWAIT);
return (err < 0) ? err : 0;
}
EXPORT_SYMBOL(rdma_nl_unicast);
int rdma_nl_unicast_wait(struct net *net, struct sk_buff *skb, __u32 pid)
{
struct rdma_dev_net *rnet = rdma_net_to_dev_net(net);
int err;
err = netlink_unicast(rnet->nl_sock, skb, pid, 0);
return (err < 0) ? err : 0;
}
EXPORT_SYMBOL(rdma_nl_unicast_wait);
int rdma_nl_multicast(struct net *net, struct sk_buff *skb,
unsigned int group, gfp_t flags)
{
struct rdma_dev_net *rnet = rdma_net_to_dev_net(net);
return nlmsg_multicast(rnet->nl_sock, skb, 0, group, flags);
}
EXPORT_SYMBOL(rdma_nl_multicast);
void rdma_nl_init(void)
{
int idx;
for (idx = 0; idx < RDMA_NL_NUM_CLIENTS; idx++)
init_rwsem(&rdma_nl_types[idx].sem);
}
void rdma_nl_exit(void)
{
int idx;
for (idx = 0; idx < RDMA_NL_NUM_CLIENTS; idx++)
WARN(rdma_nl_types[idx].cb_table,
"Netlink client %d wasn't released prior to unloading %s\n",
idx, KBUILD_MODNAME);
}
int rdma_nl_net_init(struct rdma_dev_net *rnet)
{
struct net *net = read_pnet(&rnet->net);
struct netlink_kernel_cfg cfg = {
.input = rdma_nl_rcv,
};
struct sock *nls;
nls = netlink_kernel_create(net, NETLINK_RDMA, &cfg);
if (!nls)
return -ENOMEM;
nls->sk_sndtimeo = 10 * HZ;
rnet->nl_sock = nls;
return 0;
}
void rdma_nl_net_exit(struct rdma_dev_net *rnet)
{
netlink_kernel_release(rnet->nl_sock);
}
MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_RDMA);