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mctp: perform route lookups under a RCU read-side lock 

[ Upstream commit 5093bbfc10 ]

Our current route lookups (mctp_route_lookup and mctp_route_lookup_null)
traverse the net's route list without the RCU read lock held. This means
the route lookup is subject to preemption, resulting in an potential
grace period expiry, and so an eventual kfree() while we still have the
route pointer.

Add the proper read-side critical section locks around the route
lookups, preventing premption and a possible parallel kfree.

The remaining net->mctp.routes accesses are already under a
rcu_read_lock, or protected by the RTNL for updates.

Based on an analysis from Sili Luo <rootlab@huawei.com>, where
introducing a delay in the route lookup could cause a UAF on
simultaneous sendmsg() and route deletion.

Reported-by: Sili Luo <rootlab@huawei.com>
Fixes: 889b7da23a ("mctp: Add initial routing framework")
Cc: stable@vger.kernel.org
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/29c4b0e67dc1bf3571df3982de87df90cae9b631.1696837310.git.jk@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Jeremy Kerr 2023-10-09 15:56:45 +08:00 committed by Greg Kroah-Hartman
parent db3f17e571
commit 6c52b12159
1 changed files with 16 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
net/mctp/route.c
View File

@ -549,6 +549,8 @@ struct mctp_route *mctp_route_lookup(struct net *net, unsigned int dnet,
{
struct mctp_route *tmp, *rt = NULL;
rcu_read_lock();
list_for_each_entry_rcu(tmp, &net->mctp.routes, list) {
/* TODO: add metrics */
if (mctp_rt_match_eid(tmp, dnet, daddr)) {
@ -559,21 +561,29 @@ struct mctp_route *mctp_route_lookup(struct net *net, unsigned int dnet,
}
}
rcu_read_unlock();
return rt;
}
static struct mctp_route *mctp_route_lookup_null(struct net *net,
struct net_device *dev)
{
struct mctp_route *rt;
struct mctp_route *tmp, *rt = NULL;
list_for_each_entry_rcu(rt, &net->mctp.routes, list) {
if (rt->dev->dev == dev && rt->type == RTN_LOCAL &&
refcount_inc_not_zero(&rt->refs))
return rt;
rcu_read_lock();
list_for_each_entry_rcu(tmp, &net->mctp.routes, list) {
if (tmp->dev->dev == dev && tmp->type == RTN_LOCAL &&
refcount_inc_not_zero(&tmp->refs)) {
rt = tmp;
break;
}
}
return NULL;
rcu_read_unlock();
return rt;
}
/* sends a skb to rt and releases the route. */