netlink: prevent deadlock in ctrl_dumpfamily()
Subsystems (2)
PATCH 1/1 netlink: prevent deadlock in ctrl_dumpfamily()
Commmit 58ad436fcf49810aa006016107f494c9ac9013db
Author: Johannes Berg <johannes.berg at intel.com>
genetlink: fix family dump race
added genl_lock() call to ctrl_dumpfamily(), which potentially can deadlock. Suppose the following case:
genl_rcv_msg(): !family->parallel_ops -> genl_lock()
genl_family_rcv_msg() netlink_dump_start() netlink_dump() ctrl_dumpfamily() --> genl_lock()
Take in account possibility of genl_lock() in genl_rcv_msg() and do not acquire genl_mutex in ctrl_dumpfamily() for a family that supports parallel_ops.
---
net/netlink/genetlink.c | 6 ++++++ 1 file changed, 6 insertions(+)
net/netlink/genetlink.c +6 -0
@@ -791,6 +791,12 @@ static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)int fams_to_skip = cb->args[1 ];bool need_locking = chains_to_skip || fams_to_skip; +if (need_locking) { +/* genl_mutex could be already locked in genl_rcv_msg() */ + rt =genl_family_find_byid (cb->nlh->nlmsg_type); + need_locking = need_locking && rt->parallel_ops; + } +if (need_locking)genl_lock ();
net/netlink/genetlink.c static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb) · line 798
Quoted 6 lines
net/netlink/genetlink.c +5
-0+if (need_locking) { +/* genl_mutex could be already locked in genl_rcv_msg() */ + rt =genl_family_find_byid (cb->nlh->nlmsg_type); + need_locking = need_locking && rt->parallel_ops; + }
This is equivalent to reverting the patch because parallel_ops will be false for the genl family. :-)
johannes
Signature · 8 lines
Intel GmbH Dornacher Strasse 1 85622 Feldkirchen/Muenchen, Deutschland Sitz der Gesellschaft: Feldkirchen bei Muenchen Geschaeftsfuehrer: Christian Lamprechter, Hannes Schwaderer, Douglas Lusk Registergericht: Muenchen HRB 47456 Ust.-IdNr./VAT Registration No.: DE129385895 Citibank Frankfurt a.M. (BLZ 502 109 00) 600119052
Quoted 8 lines · Johannes
net/netlink/genetlink.c static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb) · line 798
Quoted 5 lines
net/netlink/genetlink.c +5
-0+if (need_locking) { +/* genl_mutex could be already locked in genl_rcv_msg() */ + rt =genl_family_find_byid (cb->nlh->nlmsg_type); + need_locking = need_locking && rt->parallel_ops; + }This is equivalent to reverting the patch because
parallel_opswill be false for the genl family. :-)
sorry, didn't notice that there is already a thread on lkml regarding this issue. will follow that discussion. the reason was that I see an actual deadlock on my machine during certain network activities, but lockdep is silent.
thanks,
-ss
Quoted 12 lines
johannes
Signature · 8 lines
Intel GmbH Dornacher Strasse 1 85622 Feldkirchen/Muenchen, Deutschland Sitz der Gesellschaft: Feldkirchen bei Muenchen Geschaeftsfuehrer: Christian Lamprechter, Hannes Schwaderer, Douglas Lusk Registergericht: Muenchen HRB 47456 Ust.-IdNr./VAT Registration No.: DE129385895 Citibank Frankfurt a.M. (BLZ 502 109 00) 600119052