Daniel Borkmann 4e7c133068 netlink: make sure -EBUSY won't escape from netlink_insert ... Linus reports the following deadlock on rtnl_mutex; triggered only once so far (extract): [12236.694209] NetworkManager D 0000000000013b80 0 1047 1 0x00000000 [12236.694218] ffff88003f902640 0000000000000000 ffffffff815d15a9 0000000000000018 [12236.694224] ffff880119538000 ffff88003f902640 ffffffff81a8ff84 00000000ffffffff [12236.694230] ffffffff81a8ff88 ffff880119c47f00 ffffffff815d133a ffffffff81a8ff80 [12236.694235] Call Trace: [12236.694250] [<ffffffff815d15a9>] ? schedule_preempt_disabled+0x9/0x10 [12236.694257] [<ffffffff815d133a>] ? schedule+0x2a/0x70 [12236.694263] [<ffffffff815d15a9>] ? schedule_preempt_disabled+0x9/0x10 [12236.694271] [<ffffffff815d2c3f>] ? __mutex_lock_slowpath+0x7f/0xf0 [12236.694280] [<ffffffff815d2cc6>] ? mutex_lock+0x16/0x30 [12236.694291] [<ffffffff814f1f90>] ? rtnetlink_rcv+0x10/0x30 [12236.694299] [<ffffffff8150ce3b>] ? netlink_unicast+0xfb/0x180 [12236.694309] [<ffffffff814f5ad3>] ? rtnl_getlink+0x113/0x190 [12236.694319] [<ffffffff814f202a>] ? rtnetlink_rcv_msg+0x7a/0x210 [12236.694331] [<ffffffff8124565c>] ? sock_has_perm+0x5c/0x70 [12236.694339] [<ffffffff814f1fb0>] ? rtnetlink_rcv+0x30/0x30 [12236.694346] [<ffffffff8150d62c>] ? netlink_rcv_skb+0x9c/0xc0 [12236.694354] [<ffffffff814f1f9f>] ? rtnetlink_rcv+0x1f/0x30 [12236.694360] [<ffffffff8150ce3b>] ? netlink_unicast+0xfb/0x180 [12236.694367] [<ffffffff8150d344>] ? netlink_sendmsg+0x484/0x5d0 [12236.694376] [<ffffffff810a236f>] ? __wake_up+0x2f/0x50 [12236.694387] [<ffffffff814cad23>] ? sock_sendmsg+0x33/0x40 [12236.694396] [<ffffffff814cb05e>] ? ___sys_sendmsg+0x22e/0x240 [12236.694405] [<ffffffff814cab75>] ? ___sys_recvmsg+0x135/0x1a0 [12236.694415] [<ffffffff811a9d12>] ? eventfd_write+0x82/0x210 [12236.694423] [<ffffffff811a0f9e>] ? fsnotify+0x32e/0x4c0 [12236.694429] [<ffffffff8108cb70>] ? wake_up_q+0x60/0x60 [12236.694434] [<ffffffff814cba09>] ? __sys_sendmsg+0x39/0x70 [12236.694440] [<ffffffff815d4797>] ? entry_SYSCALL_64_fastpath+0x12/0x6a It seems so far plausible that the recursive call into rtnetlink_rcv() looks suspicious. One way, where this could trigger is that the senders NETLINK_CB(skb).portid was wrongly 0 (which is rtnetlink socket), so the rtnl_getlink() request's answer would be sent to the kernel instead to the actual user process, thus grabbing rtnl_mutex() twice. One theory would be that netlink_autobind() triggered via netlink_sendmsg() internally overwrites the -EBUSY error to 0, but where it is wrongly originating from __netlink_insert() instead. That would reset the socket's portid to 0, which is then filled into NETLINK_CB(skb).portid later on. As commit d470e3b483 ("[NETLINK]: Fix two socket hashing bugs.") also puts it, -EBUSY should not be propagated from netlink_insert(). It looks like it's very unlikely to reproduce. We need to trigger the rhashtable_insert_rehash() handler under a situation where rehashing currently occurs (one /rare/ way would be to hit ht->elasticity limits while not filled enough to expand the hashtable, but that would rather require a specifically crafted bind() sequence with knowledge about destination slots, seems unlikely). It probably makes sense to guard __netlink_insert() in any case and remap that error. It was suggested that EOVERFLOW might be better than an already overloaded ENOMEM. Reference: http://thread.gmane.org/gmane.linux.network/372676 Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Acked-by: Thomas Graf <tgraf@suug.ch> Signed-off-by: David S. Miller <davem@davemloft.net>		2015-08-10 10:59:10 -07:00
..
af_netlink.c	netlink: make sure -EBUSY won't escape from netlink_insert	2015-08-10 10:59:10 -07:00
af_netlink.h	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2015-01-27 16:59:56 -08:00
diag.c	netlink: make nlmsg_end() and genlmsg_end() void	2015-01-18 01:03:45 -05:00
genetlink.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2015-01-27 16:59:56 -08:00
Kconfig	netlink: kconfig: move mmap i/o into netlink kconfig	2013-05-01 15:02:42 -04:00
Makefile	netlink: Diag core and basic socket info dumping (v2)	2013-03-21 12:38:03 -04:00