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: [<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>
Florian Westphal
0470eb99b4