[PATCH 4.1 140/159] netlink: dont hold mutex in rcu callback when releasing mmapd ring

Greg Kroah-Hartman
2015-09-26T21:26:37Z

From: Florian Westphal <fw@strlen.de>

[ Upstream commit 0470eb99b4721586ccac954faac3fa4472da0845 ]

Kirill A. Shutemov says:

This simple test-case trigers few locking asserts in kernel:

int main(int argc, char **argv)
{
unsigned int block_size = 16 * 4096;
struct nl_mmap_req req = {
.nm_block_size = block_size,
.nm_block_nr = 64,
.nm_frame_size = 16384,
.nm_frame_nr = 64 * block_size / 16384,
};
unsigned int ring_size;
int fd;

fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC);
if (setsockopt(fd, SOL_NETLINK, NETLINK_RX_RING, &req, sizeof(req)) < 0)
exit(1);
if (setsockopt(fd, SOL_NETLINK, NETLINK_TX_RING, &req, sizeof(req)) < 0)
exit(1);

ring_size = req.nm_block_nr * req.nm_block_size;
mmap(NULL, 2 * ring_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
return 0;
}

+++ exited with 0 +++
BUG: sleeping function called from invalid context at /home/kas/git/public/linux-mm/kernel/locking/mutex.c:616
in_atomic(): 1, irqs_disabled(): 0, pid: 1, name: init
3 locks held by init/1:
#0: (reboot_mutex){+.+...}, at: [<ffffffff81080959>] SyS_reboot+0xa9/0x220
#1: ((reboot_notifier_list).rwsem){.+.+..}, at: [<ffffffff8107f379>] __blocking_notifier_call_chain+0x39/0x70
#2: (rcu_callback){......}, at: [<ffffffff810d32e0>] rcu_do_batch.isra.49+0x160/0x10c0
Preemption disabled at:[<ffffffff8145365f>] __delay+0xf/0x20

CPU: 1 PID: 1 Comm: init Not tainted 4.1.0-00009-gbddf4c4818e0 #253
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Debian-1.8.2-1 04/01/2014
ffff88017b3d8000 ffff88027bc03c38 ffffffff81929ceb 0000000000000102
0000000000000000 ffff88027bc03c68 ffffffff81085a9d 0000000000000002
ffffffff81ca2a20 0000000000000268 0000000000000000 ffff88027bc03c98
Call Trace:
<IRQ> [<ffffffff81929ceb>] dump_stack+0x4f/0x7b
[<ffffffff81085a9d>] ___might_sleep+0x16d/0x270
[<ffffffff81085bed>] __might_sleep+0x4d/0x90
[<ffffffff8192e96f>] mutex_lock_nested+0x2f/0x430
[<ffffffff81932fed>] ? _raw_spin_unlock_irqrestore+0x5d/0x80
[<ffffffff81464143>] ? __this_cpu_preempt_check+0x13/0x20
[<ffffffff8182fc3d>] netlink_set_ring+0x1ed/0x350
[<ffffffff8182e000>] ? netlink_undo_bind+0x70/0x70
[<ffffffff8182fe20>] netlink_sock_destruct+0x80/0x150
[<ffffffff817e484d>] __sk_free+0x1d/0x160
[<ffffffff817e49a9>] sk_free+0x19/0x20
[..]

Cong Wang says:

We can't hold mutex lock in a rcu callback, [..]

Thomas Graf says:

The socket should be dead at this point. It might be simpler to
add a netlink_release_ring() function which doesn't require
locking at all.

Reported-by: "Kirill A. Shutemov" <kirill@shutemov.name>
Diagnosed-by: Cong Wang <cwang@twopensource.com>
Suggested-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/netlink/af_netlink.c | 79 +++++++++++++++++++++++++++--------------------
1 file changed, 47 insertions(+), 32 deletions(-)

--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -355,25 +355,52 @@ err1:
return NULL;
}

+
+static void
+__netlink_set_ring(struct sock *sk, struct nl_mmap_req *req, bool tx_ring, void **pg_vec,
+ unsigned int order)
+{
+ struct netlink_sock *nlk = nlk_sk(sk);
+ struct sk_buff_head *queue;
+ struct netlink_ring *ring;
+
+ queue = tx_ring ? &sk->sk_write_queue : &sk->sk_receive_queue;
+ ring = tx_ring ? &nlk->tx_ring : &nlk->rx_ring;
+
+ spin_lock_bh(&queue->lock);
+
+ ring->frame_max = req->nm_frame_nr - 1;
+ ring->head = 0;
+ ring->frame_size = req->nm_frame_size;
+ ring->pg_vec_pages = req->nm_block_size / PAGE_SIZE;
+
+ swap(ring->pg_vec_len, req->nm_block_nr);
+ swap(ring->pg_vec_order, order);
+ swap(ring->pg_vec, pg_vec);
+
+ __skb_queue_purge(queue);
+ spin_unlock_bh(&queue->lock);
+
+ WARN_ON(atomic_read(&nlk->mapped));
+
+ if (pg_vec)
+ free_pg_vec(pg_vec, order, req->nm_block_nr);
+}
+
static int netlink_set_ring(struct sock *sk, struct nl_mmap_req *req,
- bool closing, bool tx_ring)
+ bool tx_ring)
{
struct netlink_sock *nlk = nlk_sk(sk);
struct netlink_ring *ring;
- struct sk_buff_head *queue;
void **pg_vec = NULL;
unsigned int order = 0;
- int err;

ring = tx_ring ? &nlk->tx_ring : &nlk->rx_ring;
- queue = tx_ring ? &sk->sk_write_queue : &sk->sk_receive_queue;

- if (!closing) {
- if (atomic_read(&nlk->mapped))
- return -EBUSY;
- if (atomic_read(&ring->pending))
- return -EBUSY;
- }
+ if (atomic_read(&nlk->mapped))
+ return -EBUSY;
+ if (atomic_read(&ring->pending))
+ return -EBUSY;

if (req->nm_block_nr) {
if (ring->pg_vec != NULL)
@@ -405,31 +432,19 @@ static int netlink_set_ring(struct sock
return -EINVAL;
}

- err = -EBUSY;
mutex_lock(&nlk->pg_vec_lock);
- if (closing || atomic_read(&nlk->mapped) == 0) {
- err = 0;
- spin_lock_bh(&queue->lock);
-
- ring->frame_max = req->nm_frame_nr - 1;
- ring->head = 0;
- ring->frame_size = req->nm_frame_size;
- ring->pg_vec_pages = req->nm_block_size / PAGE_SIZE;
-
- swap(ring->pg_vec_len, req->nm_block_nr);
- swap(ring->pg_vec_order, order);
- swap(ring->pg_vec, pg_vec);
-
- __skb_queue_purge(queue);
- spin_unlock_bh(&queue->lock);
-
- WARN_ON(atomic_read(&nlk->mapped));
+ if (atomic_read(&nlk->mapped) == 0) {
+ __netlink_set_ring(sk, req, tx_ring, pg_vec, order);
+ mutex_unlock(&nlk->pg_vec_lock);
+ return 0;
}
+
mutex_unlock(&nlk->pg_vec_lock);

if (pg_vec)
free_pg_vec(pg_vec, order, req->nm_block_nr);
- return err;
+
+ return -EBUSY;
}

static void netlink_mm_open(struct vm_area_struct *vma)
@@ -898,10 +913,10 @@ static void netlink_sock_destruct(struct

memset(&req, 0, sizeof(req));
if (nlk->rx_ring.pg_vec)
- netlink_set_ring(sk, &req, true, false);
+ __netlink_set_ring(sk, &req, false, NULL, 0);
memset(&req, 0, sizeof(req));
if (nlk->tx_ring.pg_vec)
- netlink_set_ring(sk, &req, true, true);
+ __netlink_set_ring(sk, &req, true, NULL, 0);
}
#endif /* CONFIG_NETLINK_MMAP */

@@ -2197,7 +2212,7 @@ static int netlink_setsockopt(struct soc
return -EINVAL;
if (copy_from_user(&req, optval, sizeof(req)))
return -EFAULT;
- err = netlink_set_ring(sk, &req, false,
+ err = netlink_set_ring(sk, &req,
optname == NETLINK_TX_RING);
break;
}