From: Alexey Dobriyan Date: Sat, 30 Jan 2010 10:05:05 +0000 (+0000) Subject: netlink: fix for too early rmmod X-Git-Tag: v2.6.33-rc8~34^2~22 X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=commitdiff_plain;h=974c37e9d88c3e5a3e56eb98cb9c84232eb2bdcb netlink: fix for too early rmmod Netlink code does module autoload if protocol userspace is asking for is not ready. However, module can dissapear right after it was autoloaded. Example: modprobe/rmmod stress-testing and xfrm_user.ko providing NETLINK_XFRM. netlink_create() in such situation _will_ create userspace socket and _will_not_ pin module. Now if module was removed and we're going to call ->netlink_rcv into nothing: BUG: unable to handle kernel paging request at ffffffffa02f842a ^^^^^^^^^^^^^^^^ modules are loaded near these addresses here IP: [] 0xffffffffa02f842a PGD 161f067 PUD 1623063 PMD baa12067 PTE 0 Oops: 0010 [#1] PREEMPT SMP DEBUG_PAGEALLOC last sysfs file: /sys/devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/uevent CPU 1 Pid: 11515, comm: ip Not tainted 2.6.33-rc5-netns-00594-gaaa5728-dirty #6 P5E/P5E RIP: 0010:[] [] 0xffffffffa02f842a RSP: 0018:ffff8800baa3db48 EFLAGS: 00010292 RAX: ffff8800baa3dfd8 RBX: ffff8800be353640 RCX: 0000000000000000 RDX: ffffffff81959380 RSI: ffff8800bab7f130 RDI: 0000000000000001 RBP: ffff8800baa3db58 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000011 R13: ffff8800be353640 R14: ffff8800bcdec240 R15: ffff8800bd488010 FS: 00007f93749656f0(0000) GS:ffff880002300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: ffffffffa02f842a CR3: 00000000ba82b000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process ip (pid: 11515, threadinfo ffff8800baa3c000, task ffff8800bab7eb30) Stack: ffffffff813637c0 ffff8800bd488000 ffff8800baa3dba8 ffffffff8136397d <0> 0000000000000000 ffffffff81344adc 7fffffffffffffff 0000000000000000 <0> ffff8800baa3ded8 ffff8800be353640 ffff8800bcdec240 0000000000000000 Call Trace: [] ? netlink_unicast+0x100/0x2d0 [] netlink_unicast+0x2bd/0x2d0 netlink_unicast_kernel: nlk->netlink_rcv(skb); [] ? memcpy_fromiovec+0x6c/0x90 [] netlink_sendmsg+0x1d3/0x2d0 [] sock_sendmsg+0xbb/0xf0 [] ? __lock_acquire+0x27b/0xa60 [] ? might_fault+0x73/0xd0 [] ? might_fault+0x73/0xd0 [] ? __lock_release+0x82/0x170 [] ? might_fault+0xbe/0xd0 [] ? might_fault+0x73/0xd0 [] ? verify_iovec+0x47/0xd0 [] sys_sendmsg+0x1a9/0x360 [] ? _raw_spin_unlock_irqrestore+0x65/0x70 [] ? trace_hardirqs_on+0xd/0x10 [] ? _raw_spin_unlock_irqrestore+0x42/0x70 [] ? __up_read+0x84/0xb0 [] ? trace_hardirqs_on_caller+0x145/0x190 [] ? trace_hardirqs_on_thunk+0x3a/0x3f [] system_call_fastpath+0x16/0x1b Code: Bad RIP value. RIP [] 0xffffffffa02f842a RSP CR2: ffffffffa02f842a If module was quickly removed after autoloading, return -E. Return -EPROTONOSUPPORT if module was quickly removed after autoloading. Signed-off-by: Alexey Dobriyan Signed-off-by: David S. Miller --- diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index a4957bf..4c5972b 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -455,9 +455,14 @@ static int netlink_create(struct net *net, struct socket *sock, int protocol, if (nl_table[protocol].registered && try_module_get(nl_table[protocol].module)) module = nl_table[protocol].module; + else + err = -EPROTONOSUPPORT; cb_mutex = nl_table[protocol].cb_mutex; netlink_unlock_table(); + if (err < 0) + goto out; + err = __netlink_create(net, sock, cb_mutex, protocol); if (err < 0) goto out_module;