On Tue, Oct 15, 2019 at 11:07:33AM +0300, Leon Romanovsky wrote:
> diff --git a/drivers/infiniband/core/netlink.c b/drivers/infiniband/core/netlink.c
> index 81dbd5f41bed..a3507b8be569 100644
> +++ b/drivers/infiniband/core/netlink.c
> @@ -42,9 +42,12 @@
> #include <linux/module.h>
> #include "core_priv.h"
>
> -static DEFINE_MUTEX(rdma_nl_mutex);
> static struct {
> - const struct rdma_nl_cbs *cb_table;
> + const struct rdma_nl_cbs __rcu *cb_table;
> + /* Synchronizes between ongoing netlink commands and netlink client
> + * unregistration.
> + */
> + struct srcu_struct unreg_srcu;
A srcu in every index is serious overkill for this. Lets just us a
rwsem:
>From 3ab38b889ab6b85b8689a8cd9bccbf2b28711677 Mon Sep 17 00:00:00 2001
From: Parav Pandit <parav@xxxxxxxxxxxx>
Date: Tue, 15 Oct 2019 11:07:33 +0300
Subject: [PATCH] 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: 0e2d00eb6fd45 ("RDMA: Add NLDEV_GET_CHARDEV to allow char dev discovery and autoload")
Link: https://lore.kernel.org/r/20191015080733.18625-1-leon@xxxxxxxxxx
Signed-off-by: Parav Pandit <parav@xxxxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
---
drivers/infiniband/core/core_priv.h | 1 +
drivers/infiniband/core/device.c | 2 +
drivers/infiniband/core/netlink.c | 107 ++++++++++++++--------------
3 files changed, 56 insertions(+), 54 deletions(-)
diff --git a/drivers/infiniband/core/core_priv.h b/drivers/infiniband/core/core_priv.h
index 3a8b0911c3bc16..9d07378b5b4230 100644
--- a/drivers/infiniband/core/core_priv.h
+++ b/drivers/infiniband/core/core_priv.h
@@ -199,6 +199,7 @@ void ib_mad_cleanup(void);
int ib_sa_init(void);
void ib_sa_cleanup(void);
+void rdma_nl_init(void);
void rdma_nl_exit(void);
int ib_nl_handle_resolve_resp(struct sk_buff *skb,
diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index 2dd2cfe9b56136..50a92442c4f7c1 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -2716,6 +2716,8 @@ static int __init ib_core_init(void)
goto err_comp_unbound;
}
+ rdma_nl_init();
+
ret = addr_init();
if (ret) {
pr_warn("Could't init IB address resolution\n");
diff --git a/drivers/infiniband/core/netlink.c b/drivers/infiniband/core/netlink.c
index 81dbd5f41beda2..8cd31ef25eff20 100644
--- a/drivers/infiniband/core/netlink.c
+++ b/drivers/infiniband/core/netlink.c
@@ -42,9 +42,12 @@
#include <linux/module.h>
#include "core_priv.h"
-static DEFINE_MUTEX(rdma_nl_mutex);
static struct {
- const struct rdma_nl_cbs *cb_table;
+ 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)
@@ -75,70 +78,53 @@ static bool is_nl_msg_valid(unsigned int type, unsigned int op)
return (op < max_num_ops[type]) ? true : false;
}
-static bool
-is_nl_valid(const struct sk_buff *skb, unsigned int type, unsigned int op)
+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;
- if (!is_nl_msg_valid(type, op))
- return false;
-
/*
* 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 false;
+ return NULL;
- if (!rdma_nl_types[type].cb_table) {
- mutex_unlock(&rdma_nl_mutex);
- request_module("rdma-netlink-subsys-%d", type);
- mutex_lock(&rdma_nl_mutex);
- }
+ 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);
- cb_table = rdma_nl_types[type].cb_table;
+ 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 false;
- return true;
+ return NULL;
+ return cb_table;
}
void rdma_nl_register(unsigned int index,
const struct rdma_nl_cbs cb_table[])
{
- mutex_lock(&rdma_nl_mutex);
- if (!is_nl_msg_valid(index, 0)) {
- /*
- * All clients are not interesting in success/failure of
- * this call. They want to see the print to error log and
- * continue their initialization. Print warning for them,
- * because it is programmer's error to be here.
- */
- mutex_unlock(&rdma_nl_mutex);
- WARN(true,
- "The not-valid %u index was supplied to RDMA netlink\n",
- index);
+ if (WARN_ON(!is_nl_msg_valid(index, 0)) ||
+ WARN_ON(READ_ONCE(rdma_nl_types[index].cb_table)))
return;
- }
-
- if (rdma_nl_types[index].cb_table) {
- mutex_unlock(&rdma_nl_mutex);
- WARN(true,
- "The %u index is already registered in RDMA netlink\n",
- index);
- return;
- }
- rdma_nl_types[index].cb_table = cb_table;
- mutex_unlock(&rdma_nl_mutex);
+ /* 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)
{
- mutex_lock(&rdma_nl_mutex);
+ down_write(&rdma_nl_types[index].sem);
rdma_nl_types[index].cb_table = NULL;
- mutex_unlock(&rdma_nl_mutex);
+ up_write(&rdma_nl_types[index].sem);
}
EXPORT_SYMBOL(rdma_nl_unregister);
@@ -170,15 +156,21 @@ static int rdma_nl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
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_valid(skb, index, op))
+ if (!is_nl_msg_valid(index, op))
return -EINVAL;
- cb_table = rdma_nl_types[index].cb_table;
+ 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))
- return -EPERM;
+ !netlink_capable(skb, CAP_NET_ADMIN)) {
+ err = -EPERM;
+ goto done;
+ }
/*
* LS responses overload the 0x100 (NLM_F_ROOT) flag. Don't
@@ -186,8 +178,8 @@ static int rdma_nl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
*/
if (index == RDMA_NL_LS) {
if (cb_table[op].doit)
- return cb_table[op].doit(skb, nlh, extack);
- return -EINVAL;
+ 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) {
@@ -195,14 +187,15 @@ static int rdma_nl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
.dump = cb_table[op].dump,
};
if (c.dump)
- return netlink_dump_start(skb->sk, skb, nlh, &c);
- return -EINVAL;
+ err = netlink_dump_start(skb->sk, skb, nlh, &c);
+ goto done;
}
if (cb_table[op].doit)
- return cb_table[op].doit(skb, nlh, extack);
-
- return 0;
+ err = cb_table[op].doit(skb, nlh, extack);
+done:
+ up_read(&rdma_nl_types[index].sem);
+ return err;
}
/*
@@ -263,9 +256,7 @@ static int rdma_nl_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
static void rdma_nl_rcv(struct sk_buff *skb)
{
- mutex_lock(&rdma_nl_mutex);
rdma_nl_rcv_skb(skb, &rdma_nl_rcv_msg);
- mutex_unlock(&rdma_nl_mutex);
}
int rdma_nl_unicast(struct net *net, struct sk_buff *skb, u32 pid)
@@ -297,6 +288,14 @@ int rdma_nl_multicast(struct net *net, struct sk_buff *skb,
}
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;
--
2.23.0
