In the Linux kernel, the following vulnerability has been resolved:
net/smc: reduce rtnl pressure in smc_pnet_create_pnetids_list()
Many syzbot reports show extreme rtnl pressure, and many of them hint
that smc acquires rtnl in netns creation for no good reason [1]
This patch returns early from smc_pnet_net_init()
if there is no netdevice yet.
I am not even sure why smc_pnet_create_pnetids_list() even exists,
because smc_pnet_netdev_event() is also calling
smc_pnet_add_base_pnetid() when handling NETDEV_UP event.
[1] extract of typical syzbot reports
2 locks held by syz-executor.3/12252:
#0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline]
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878
2 locks held by syz-executor.4/12253:
#0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline]
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878
2 locks held by syz-executor.1/12257:
#0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline]
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878
2 locks held by syz-executor.2/12261:
#0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline]
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878
2 locks held by syz-executor.0/12265:
#0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline]
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878
2 locks held by syz-executor.3/12268:
#0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline]
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878
2 locks held by syz-executor.4/12271:
#0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline]
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878
2 locks held by syz-executor.1/12274:
#0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline]
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878
2 locks held by syz-executor.2/12280:
#0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline]
#1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878
Additional Descriptions (1)
En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net/smc: reduce la presión rtnl en smc_pnet_create_pnetids_list() Muchos informes de syzbot muestran una presión rtnl extrema, y muchos de ellos insinúan que smc adquiere rtnl en la creación de netns sin una buena razón [1] Este parche regresa temprano desde smc_pnet_net_init() si aún no hay un netdevice. Ni siquiera estoy seguro de por qué existe smc_pnet_create_pnetids_list(), porque smc_pnet_netdev_event() también llama a smc_pnet_add_base_pnetid() cuando maneja el evento NETDEV_UP. [1] extracto de informes típicos de syzbot 2 bloqueos mantenidos por syz-executor.3/12252: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, en: copy_net_ns+0x4c7/0x7b0 net/core /net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [en línea] #1: ffffffff8f375b88 (rtnl_mutex){+ .+.}-{3:3}, en: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 bloqueos retenidos por syz-executor.4/12253: #0: ffffffff8f369610 (pernet_ops_rwsem){+++ +}-{3:3}, en: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_create_pnetids_list net/ smc/smc_pnet.c:809 [en línea] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 bloqueos retenidos por syz-executor.1/12257: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, en: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex ){+.+.}-{3:3}, en: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [en línea] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en : smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 bloqueos retenidos por syz-executor.2/12261: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, en: copy_net_ns +0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [en línea] #1 : ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 bloqueos retenidos por syz-executor.0/12265: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, en: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3 }, en: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [en línea] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet. c:878 2 bloqueos retenidos por syz-executor.3/12268: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, en: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c: 491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [en línea] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}- {3:3}, en: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 bloqueos retenidos por syz-executor.4/12271: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3 :3}, en: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_create_pnetids_list net/smc/smc_pnet.c :809 [en línea] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 bloqueos retenidos por syz-executor.1 /12274: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, en: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+ .}-{3:3}, en: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [en línea] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_net_init+0x10a/ 0x1e0 net/smc/smc_pnet.c:878 2 bloqueos retenidos por syz-executor.2/12280: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, en: copy_net_ns+0x4c7/0x7b0 net /core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, en: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [en línea] #1: ffffffff8f375b88 (rtnl_mutex) {+.+.}-{3:3}, en: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878