Re: [PATCH net v2] tipc: fix missing RTNL lock protection during setting link properties
flat view
From: Kirill Tkhai <hidden>
Date: 2018-02-12 10:10:42
Hi, Ying, On 12.02.2018 11:56, Ying Xue wrote:
quoted hunk ↗ jump to hunk
Currently when user changes link properties, TIPC first checks if user's command message contains media name or bearer name through tipc_media_find() or tipc_bearer_find() which is protected by RTNL lock. But when tipc_nl_compat_link_set() conducts the checking with the two functions, it doesn't hold RTNL lock at all, as a result, the following complaints were reported: audit: type=1400 audit(1514679888.244:9): avc: denied { write } for pid=3194 comm="syzkaller021477" path="socket:[11143]" dev="sockfs" ino=11143 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1 ============================= WARNING: suspicious RCU usage 4.15.0-rc5+ #152 Not tainted ----------------------------- net/tipc/bearer.c:177 suspicious rcu_dereference_protected() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 2 locks held by syzkaller021477/3194: #0: (cb_lock){++++}, at: [<00000000d20133ea>] genl_rcv+0x19/0x40 net/netlink/genetlink.c:634 #1: (genl_mutex){+.+.}, at: [<00000000fcc5d1bc>] genl_lock net/netlink/genetlink.c:33 [inline] #1: (genl_mutex){+.+.}, at: [<00000000fcc5d1bc>] genl_rcv_msg+0x115/0x140 net/netlink/genetlink.c:622 stack backtrace: CPU: 1 PID: 3194 Comm: syzkaller021477 Not tainted 4.15.0-rc5+ #152 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4585 tipc_bearer_find+0x2b4/0x3b0 net/tipc/bearer.c:177 tipc_nl_compat_link_set+0x329/0x9f0 net/tipc/netlink_compat.c:729 __tipc_nl_compat_doit net/tipc/netlink_compat.c:288 [inline] tipc_nl_compat_doit+0x15b/0x660 net/tipc/netlink_compat.c:335 tipc_nl_compat_handle net/tipc/netlink_compat.c:1119 [inline] tipc_nl_compat_recv+0x112f/0x18f0 net/tipc/netlink_compat.c:1201 genl_family_rcv_msg+0x7b7/0xfb0 net/netlink/genetlink.c:599 genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:624 netlink_rcv_skb+0x21e/0x460 net/netlink/af_netlink.c:2408 genl_rcv+0x28/0x40 net/netlink/genetlink.c:635 netlink_unicast_kernel net/netlink/af_netlink.c:1275 [inline] netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1301 netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1864 sock_sendmsg_nosec net/socket.c:636 [inline] sock_sendmsg+0xca/0x110 net/socket.c:646 sock_write_iter+0x31a/0x5d0 net/socket.c:915 call_write_iter include/linux/fs.h:1772 [inline] new_sync_write fs/read_write.c:469 [inline] __vfs_write+0x684/0x970 fs/read_write.c:482 vfs_write+0x189/0x510 fs/read_write.c:544 SYSC_write fs/read_write.c:589 [inline] SyS_write+0xef/0x220 fs/read_write.c:581 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline] do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129 In order to correct the mistake, __tipc_nl_compat_doit() has been protected by RTNL lock, which means the whole operation of setting bearer/media properties is under RTNL protection. Signed-off-by: Ying Xue <redacted> Reported-by: syzbot <redacted> --- v2: The whole operation of setting bearer/media properties has been protected under RTNL, as per feedback from David M. net/tipc/bearer.c | 84 ++++++++++++++++++++++++++++++----------------- net/tipc/bearer.h | 4 +++ net/tipc/net.c | 15 +++++++-- net/tipc/net.h | 1 + net/tipc/netlink_compat.c | 14 ++++---- 5 files changed, 79 insertions(+), 39 deletions(-)diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c index c800147..e12d7eb 100644 --- a/net/tipc/bearer.c +++ b/net/tipc/bearer.c@@ -813,7 +813,7 @@ int tipc_nl_bearer_get(struct sk_buff *skb, struct genl_info *info) return err; } -int tipc_nl_bearer_disable(struct sk_buff *skb, struct genl_info *info) +int __tipc_nl_bearer_disable(struct sk_buff *skb, struct genl_info *info) { int err; char *name;@@ -835,20 +835,27 @@ int tipc_nl_bearer_disable(struct sk_buff *skb, struct genl_info *info) name = nla_data(attrs[TIPC_NLA_BEARER_NAME]); - rtnl_lock(); bearer = tipc_bearer_find(net, name); - if (!bearer) { - rtnl_unlock(); + if (!bearer) return -EINVAL; - } bearer_disable(net, bearer); - rtnl_unlock(); return 0; } -int tipc_nl_bearer_enable(struct sk_buff *skb, struct genl_info *info) +int tipc_nl_bearer_disable(struct sk_buff *skb, struct genl_info *info) +{ + int err; + + rtnl_lock(); + err = __tipc_nl_bearer_disable(skb, info); + rtnl_unlock(); + + return err; +} + +int __tipc_nl_bearer_enable(struct sk_buff *skb, struct genl_info *info) { int err; char *bearer;@@ -890,17 +897,24 @@ int tipc_nl_bearer_enable(struct sk_buff *skb, struct genl_info *info) prio = nla_get_u32(props[TIPC_NLA_PROP_PRIO]); } - rtnl_lock(); err = tipc_enable_bearer(net, bearer, domain, prio, attrs); - if (err) { - rtnl_unlock(); + if (err) return err; - } - rtnl_unlock(); return 0;
This err branch looks excess. It was before your patch, but in case of you change this place, can't we stop having it? it looks like we can simply do the below here: err = tipc_enable_bearer(net, bearer, domain, prio, attrs); return err;
quoted hunk ↗ jump to hunk
} +int tipc_nl_bearer_enable(struct sk_buff *skb, struct genl_info *info) +{ + int err; + + rtnl_lock(); + err = __tipc_nl_bearer_enable(skb, info); + rtnl_unlock(); + + return err; +} + int tipc_nl_bearer_add(struct sk_buff *skb, struct genl_info *info) { int err;@@ -944,7 +958,7 @@ int tipc_nl_bearer_add(struct sk_buff *skb, struct genl_info *info) return 0; } -int tipc_nl_bearer_set(struct sk_buff *skb, struct genl_info *info) +int __tipc_nl_bearer_set(struct sk_buff *skb, struct genl_info *info) { int err; char *name;@@ -965,22 +979,17 @@ int tipc_nl_bearer_set(struct sk_buff *skb, struct genl_info *info) return -EINVAL; name = nla_data(attrs[TIPC_NLA_BEARER_NAME]); - rtnl_lock(); b = tipc_bearer_find(net, name); - if (!b) { - rtnl_unlock(); + if (!b) return -EINVAL; - } if (attrs[TIPC_NLA_BEARER_PROP]) { struct nlattr *props[TIPC_NLA_PROP_MAX + 1]; err = tipc_nl_parse_link_prop(attrs[TIPC_NLA_BEARER_PROP], props); - if (err) { - rtnl_unlock(); + if (err) return err; - } if (props[TIPC_NLA_PROP_TOL]) b->tolerance = nla_get_u32(props[TIPC_NLA_PROP_TOL]);@@ -989,11 +998,21 @@ int tipc_nl_bearer_set(struct sk_buff *skb, struct genl_info *info) if (props[TIPC_NLA_PROP_WIN]) b->window = nla_get_u32(props[TIPC_NLA_PROP_WIN]); } - rtnl_unlock(); return 0; } +int tipc_nl_bearer_set(struct sk_buff *skb, struct genl_info *info) +{ + int err; + + rtnl_lock(); + err = __tipc_nl_bearer_set(skb, info); + rtnl_unlock(); + + return err; +} + static int __tipc_nl_add_media(struct tipc_nl_msg *msg, struct tipc_media *media, int nlflags) {@@ -1115,7 +1134,7 @@ int tipc_nl_media_get(struct sk_buff *skb, struct genl_info *info) return err; } -int tipc_nl_media_set(struct sk_buff *skb, struct genl_info *info) +int __tipc_nl_media_set(struct sk_buff *skb, struct genl_info *info) { int err; char *name;@@ -1133,22 +1152,17 @@ int tipc_nl_media_set(struct sk_buff *skb, struct genl_info *info) return -EINVAL; name = nla_data(attrs[TIPC_NLA_MEDIA_NAME]); - rtnl_lock(); m = tipc_media_find(name); - if (!m) { - rtnl_unlock(); + if (!m) return -EINVAL; - } if (attrs[TIPC_NLA_MEDIA_PROP]) { struct nlattr *props[TIPC_NLA_PROP_MAX + 1]; err = tipc_nl_parse_link_prop(attrs[TIPC_NLA_MEDIA_PROP], props); - if (err) { - rtnl_unlock(); + if (err) return err; - } if (props[TIPC_NLA_PROP_TOL]) m->tolerance = nla_get_u32(props[TIPC_NLA_PROP_TOL]);@@ -1157,7 +1171,17 @@ int tipc_nl_media_set(struct sk_buff *skb, struct genl_info *info) if (props[TIPC_NLA_PROP_WIN]) m->window = nla_get_u32(props[TIPC_NLA_PROP_WIN]); } - rtnl_unlock(); return 0; } + +int tipc_nl_media_set(struct sk_buff *skb, struct genl_info *info) +{ + int err; + + rtnl_lock(); + err = __tipc_nl_media_set(skb, info); + rtnl_unlock(); + + return err; +}diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h index 42d6eee..a53613d 100644 --- a/net/tipc/bearer.h +++ b/net/tipc/bearer.h@@ -188,15 +188,19 @@ extern struct tipc_media udp_media_info; #endif int tipc_nl_bearer_disable(struct sk_buff *skb, struct genl_info *info); +int __tipc_nl_bearer_disable(struct sk_buff *skb, struct genl_info *info); int tipc_nl_bearer_enable(struct sk_buff *skb, struct genl_info *info); +int __tipc_nl_bearer_enable(struct sk_buff *skb, struct genl_info *info); int tipc_nl_bearer_dump(struct sk_buff *skb, struct netlink_callback *cb); int tipc_nl_bearer_get(struct sk_buff *skb, struct genl_info *info); int tipc_nl_bearer_set(struct sk_buff *skb, struct genl_info *info); +int __tipc_nl_bearer_set(struct sk_buff *skb, struct genl_info *info); int tipc_nl_bearer_add(struct sk_buff *skb, struct genl_info *info); int tipc_nl_media_dump(struct sk_buff *skb, struct netlink_callback *cb); int tipc_nl_media_get(struct sk_buff *skb, struct genl_info *info); int tipc_nl_media_set(struct sk_buff *skb, struct genl_info *info); +int __tipc_nl_media_set(struct sk_buff *skb, struct genl_info *info); int tipc_media_set_priority(const char *name, u32 new_value); int tipc_media_set_window(const char *name, u32 new_value);diff --git a/net/tipc/net.c b/net/tipc/net.c index 719c592..1a2fde0 100644 --- a/net/tipc/net.c +++ b/net/tipc/net.c@@ -200,7 +200,7 @@ int tipc_nl_net_dump(struct sk_buff *skb, struct netlink_callback *cb) return skb->len; } -int tipc_nl_net_set(struct sk_buff *skb, struct genl_info *info) +int __tipc_nl_net_set(struct sk_buff *skb, struct genl_info *info) { struct net *net = sock_net(skb->sk); struct tipc_net *tn = net_generic(net, tipc_net_id);@@ -241,10 +241,19 @@ int tipc_nl_net_set(struct sk_buff *skb, struct genl_info *info) if (!tipc_addr_node_valid(addr)) return -EINVAL; - rtnl_lock(); tipc_net_start(net, addr); - rtnl_unlock(); } return 0; } + +int tipc_nl_net_set(struct sk_buff *skb, struct genl_info *info) +{ + int err; + + rtnl_lock(); + err = __tipc_nl_net_set(skb, info); + rtnl_unlock(); + + return err; +}diff --git a/net/tipc/net.h b/net/tipc/net.h index c7c2549..c0306aa 100644 --- a/net/tipc/net.h +++ b/net/tipc/net.h@@ -47,5 +47,6 @@ void tipc_net_stop(struct net *net); int tipc_nl_net_dump(struct sk_buff *skb, struct netlink_callback *cb); int tipc_nl_net_set(struct sk_buff *skb, struct genl_info *info); +int __tipc_nl_net_set(struct sk_buff *skb, struct genl_info *info); #endifdiff --git a/net/tipc/netlink_compat.c b/net/tipc/netlink_compat.c index e48f0b2..750e37c 100644 --- a/net/tipc/netlink_compat.c +++ b/net/tipc/netlink_compat.c@@ -332,7 +332,9 @@ static int tipc_nl_compat_doit(struct tipc_nl_compat_cmd_doit *cmd, if (msg->req_type && !TLV_CHECK_TYPE(msg->req, msg->req_type)) return -EINVAL; + rtnl_lock(); err = __tipc_nl_compat_doit(cmd, msg); + rtnl_unlock();
rtnl_lock() is frequently accessed mutex used everywhere in network subsystem, and it would be good to minimize the time it's held. Function __tipc_nl_compat_doit() allocates memory and these allocations may envoke memory reclain, which may take much time. The lock will be held all the time, and it's bad for other rtnl users. Since __tipc_nl_compat_doit() allocates constant amount of memory, we can do all the allocations before taking rtnl_lock, and this may reduce the time we are owning the lock in significant way. Can't we do this in this patchset? (I don't think we can do this in the same patch, but one more pre-patch may be introduced). The same for kfree*() and memset(), they also do not need rtnl_lock().
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if (err) return err;@@ -722,13 +724,13 @@ static int tipc_nl_compat_link_set(struct tipc_nl_compat_cmd_doit *cmd, media = tipc_media_find(lc->name); if (media) { - cmd->doit = &tipc_nl_media_set; + cmd->doit = &__tipc_nl_media_set; return tipc_nl_compat_media_set(skb, msg); } bearer = tipc_bearer_find(msg->net, lc->name); if (bearer) { - cmd->doit = &tipc_nl_bearer_set; + cmd->doit = &__tipc_nl_bearer_set; return tipc_nl_compat_bearer_set(skb, msg); }@@ -1089,12 +1091,12 @@ static int tipc_nl_compat_handle(struct tipc_nl_compat_msg *msg) return tipc_nl_compat_dumpit(&dump, msg); case TIPC_CMD_ENABLE_BEARER: msg->req_type = TIPC_TLV_BEARER_CONFIG; - doit.doit = tipc_nl_bearer_enable; + doit.doit = __tipc_nl_bearer_enable; doit.transcode = tipc_nl_compat_bearer_enable; return tipc_nl_compat_doit(&doit, msg); case TIPC_CMD_DISABLE_BEARER: msg->req_type = TIPC_TLV_BEARER_NAME; - doit.doit = tipc_nl_bearer_disable; + doit.doit = __tipc_nl_bearer_disable; doit.transcode = tipc_nl_compat_bearer_disable; return tipc_nl_compat_doit(&doit, msg); case TIPC_CMD_SHOW_LINK_STATS:@@ -1148,12 +1150,12 @@ static int tipc_nl_compat_handle(struct tipc_nl_compat_msg *msg) return tipc_nl_compat_dumpit(&dump, msg); case TIPC_CMD_SET_NODE_ADDR: msg->req_type = TIPC_TLV_NET_ADDR; - doit.doit = tipc_nl_net_set; + doit.doit = __tipc_nl_net_set; doit.transcode = tipc_nl_compat_net_set; return tipc_nl_compat_doit(&doit, msg); case TIPC_CMD_SET_NETID: msg->req_type = TIPC_TLV_UNSIGNED; - doit.doit = tipc_nl_net_set; + doit.doit = __tipc_nl_net_set; doit.transcode = tipc_nl_compat_net_set; return tipc_nl_compat_doit(&doit, msg); case TIPC_CMD_GET_NETID:
Thanks, Kirill