6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sabrina Dubroca [ Upstream commit 629ec78ef8608d955ce217880cdc3e1873af3a15 ] The RCU-protected codepaths (mpls_forward, mpls_dump_routes) can have an inconsistent view of platform_labels vs platform_label in case of a concurrent resize (resize_platform_label_table, under platform_mutex). This can lead to OOB accesses. This patch adds a seqcount, so that we get a consistent snapshot. Note that mpls_label_ok is also susceptible to this, so the check against RTA_DST in rtm_to_route_config, done outside platform_mutex, is not sufficient. This value gets passed to mpls_label_ok once more in both mpls_route_add and mpls_route_del, so there is no issue, but that additional check must not be removed. Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Fixes: 7720c01f3f590 ("mpls: Add a sysctl to control the size of the mpls label table") Fixes: dde1b38e873c ("mpls: Convert mpls_dump_routes() to RCU.") Signed-off-by: Sabrina Dubroca Link: https://patch.msgid.link/cd8fca15e3eb7e212b094064cd83652e20fd9d31.1774284088.git.sd@queasysnail.net Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- include/net/netns/mpls.h | 2 ++ net/mpls/af_mpls.c | 35 ++++++++++++++++++++++++++++------- 2 files changed, 30 insertions(+), 7 deletions(-) diff --git a/include/net/netns/mpls.h b/include/net/netns/mpls.h index 19ad2574b267c..9b83b7f43d83b 100644 --- a/include/net/netns/mpls.h +++ b/include/net/netns/mpls.h @@ -7,6 +7,7 @@ #define __NETNS_MPLS_H__ #include +#include struct mpls_route; struct ctl_table_header; @@ -16,6 +17,7 @@ struct netns_mpls { int default_ttl; size_t platform_labels; struct mpls_route __rcu * __rcu *platform_label; + seqcount_t platform_label_seq; struct ctl_table_header *ctl; }; diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c index 9685405d744b9..b94ea43b965d1 100644 --- a/net/mpls/af_mpls.c +++ b/net/mpls/af_mpls.c @@ -75,16 +75,31 @@ static void rtmsg_lfib(int event, u32 label, struct mpls_route *rt, struct nlmsghdr *nlh, struct net *net, u32 portid, unsigned int nlm_flags); +static struct mpls_route __rcu **mpls_platform_label_rcu(struct net *net, size_t *platform_labels) +{ + struct mpls_route __rcu **platform_label; + unsigned int sequence; + + do { + sequence = read_seqcount_begin(&net->mpls.platform_label_seq); + platform_label = rcu_dereference_rtnl(net->mpls.platform_label); + *platform_labels = net->mpls.platform_labels; + } while (read_seqcount_retry(&net->mpls.platform_label_seq, sequence)); + + return platform_label; +} + static struct mpls_route *mpls_route_input_rcu(struct net *net, unsigned index) { - struct mpls_route *rt = NULL; + struct mpls_route __rcu **platform_label; + size_t platform_labels; - if (index < net->mpls.platform_labels) { - struct mpls_route __rcu **platform_label = - rcu_dereference_rtnl(net->mpls.platform_label); - rt = rcu_dereference_rtnl(platform_label[index]); - } - return rt; + platform_label = mpls_platform_label_rcu(net, &platform_labels); + + if (index >= platform_labels) + return NULL; + + return rcu_dereference_rtnl(platform_label[index]); } bool mpls_output_possible(const struct net_device *dev) @@ -2583,8 +2598,12 @@ static int resize_platform_label_table(struct net *net, size_t limit) } /* Update the global pointers */ + local_bh_disable(); + write_seqcount_begin(&net->mpls.platform_label_seq); net->mpls.platform_labels = limit; rcu_assign_pointer(net->mpls.platform_label, labels); + write_seqcount_end(&net->mpls.platform_label_seq); + local_bh_enable(); rtnl_unlock(); @@ -2665,6 +2684,8 @@ static int mpls_net_init(struct net *net) struct ctl_table *table; int i; + seqcount_init(&net->mpls.platform_label_seq); + net->mpls.platform_labels = 0; net->mpls.platform_label = NULL; net->mpls.ip_ttl_propagate = 1; -- 2.53.0