From 0470eb99b4721586ccac954faac3fa4472da0845 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Tue, 21 Jul 2015 16:33:50 +0200 Subject: [PATCH] netlink: don't hold mutex in rcu callback when releasing mmapd ring 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: [] SyS_reboot+0xa9/0x220 #1: ((reboot_notifier_list).rwsem){.+.+..}, at: [] __blocking_notifier_call_chain+0x39/0x70 #2: (rcu_callback){......}, at: [] rcu_do_batch.isra.49+0x160/0x10c0 Preemption disabled at:[] __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: [] dump_stack+0x4f/0x7b [] ___might_sleep+0x16d/0x270 [] __might_sleep+0x4d/0x90 [] mutex_lock_nested+0x2f/0x430 [] ? _raw_spin_unlock_irqrestore+0x5d/0x80 [] ? __this_cpu_preempt_check+0x13/0x20 [] netlink_set_ring+0x1ed/0x350 [] ? netlink_undo_bind+0x70/0x70 [] netlink_sock_destruct+0x80/0x150 [] __sk_free+0x1d/0x160 [] 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" Diagnosed-by: Cong Wang Suggested-by: Thomas Graf Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- net/netlink/af_netlink.c | 79 ++++++++++++++++++++++++---------------- 1 file changed, 47 insertions(+), 32 deletions(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 9a0ae7172f92..d8e2e3918ce2 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -357,25 +357,52 @@ 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) @@ -407,31 +434,19 @@ static int netlink_set_ring(struct sock *sk, struct nl_mmap_req *req, 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) @@ -900,10 +915,10 @@ static void netlink_sock_destruct(struct sock *sk) 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 */ @@ -2223,7 +2238,7 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname, 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; } -- 2.34.1