diff mbox series

[net-next,v3,2/7] devlink: call peernet2id_alloc() with net pointer under RCU read lock

Message ID 20231013121029.353351-3-jiri@resnulli.us (mailing list archive)
State Accepted
Commit c503bc7df602257e9d03851654a347649a33f3c3
Delegated to: Netdev Maintainers
Headers show
Series devlink: fix a deadlock when taking devlink instance lock while holding RTNL lock | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1362 this patch: 1362
netdev/cc_maintainers success CCed 6 of 6 maintainers
netdev/build_clang success Errors and warnings before: 1386 this patch: 1386
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 1387 this patch: 1387
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 27 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Jiri Pirko Oct. 13, 2023, 12:10 p.m. UTC 
From: Jiri Pirko <jiri@nvidia.com>

peernet2id_alloc() allows to be called lockless with peer net pointer
obtained in RCU critical section and makes sure to return ns ID if net
namespaces is not being removed concurrently. Benefit from
read_pnet_rcu() helper addition, use it to obtain net pointer under RCU
read lock and pass it to peernet2id_alloc() to get ns ID.

Fixes: c137743bce02 ("devlink: introduce object and nested devlink relationship infra")
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
---
v2->v3:
- added fixes tag
v1->v2:
- moved the netns related bits from "devlink: don't take instance lock
  for nested handle put"
- fixed the code using RCU to avoid use after free of peer net struct
---
 net/devlink/netlink.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

Comments

Simon Horman Oct. 17, 2023, 8:50 a.m. UTC | #1 
On Fri, Oct 13, 2023 at 02:10:24PM +0200, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@nvidia.com>
> 
> peernet2id_alloc() allows to be called lockless with peer net pointer
> obtained in RCU critical section and makes sure to return ns ID if net
> namespaces is not being removed concurrently. Benefit from
> read_pnet_rcu() helper addition, use it to obtain net pointer under RCU
> read lock and pass it to peernet2id_alloc() to get ns ID.
> 
> Fixes: c137743bce02 ("devlink: introduce object and nested devlink relationship infra")
> Signed-off-by: Jiri Pirko <jiri@nvidia.com>

Reviewed-by: Simon Horman <horms@kernel.org>
diff mbox series

Patch

diff --git a/net/devlink/netlink.c b/net/devlink/netlink.c
index 499304d9de49..809bfc3ba8c4 100644
--- a/net/devlink/netlink.c
+++ b/net/devlink/netlink.c
@@ -86,18 +86,24 @@  int devlink_nl_put_nested_handle(struct sk_buff *msg, struct net *net,
 				 struct devlink *devlink, int attrtype)
 {
 	struct nlattr *nested_attr;
+	struct net *devl_net;
 
 	nested_attr = nla_nest_start(msg, attrtype);
 	if (!nested_attr)
 		return -EMSGSIZE;
 	if (devlink_nl_put_handle(msg, devlink))
 		goto nla_put_failure;
-	if (!net_eq(net, devlink_net(devlink))) {
-		int id = peernet2id_alloc(net, devlink_net(devlink),
-					  GFP_KERNEL);
 
+	rcu_read_lock();
+	devl_net = read_pnet_rcu(&devlink->_net);
+	if (!net_eq(net, devl_net)) {
+		int id = peernet2id_alloc(net, devl_net, GFP_ATOMIC);
+
+		rcu_read_unlock();
 		if (nla_put_s32(msg, DEVLINK_ATTR_NETNS_ID, id))
 			return -EMSGSIZE;
+	} else {
+		rcu_read_unlock();
 	}
 
 	nla_nest_end(msg, nested_attr);