diff mbox series

[v1,net-next,6/6] arp: Convert ioctl(SIOCGARP) to RCU.

Message ID 20240422194755.4221-7-kuniyu@amazon.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series arp: Random clean up and RCU conversion for ioctl(SIOCGARP). | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
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: 928 this patch: 928
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 5 of 5 maintainers
netdev/build_clang success Errors and warnings before: 938 this patch: 938
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 No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 939 this patch: 939
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 65 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-04-24--15-00 (tests: 995)

Commit Message

Kuniyuki Iwashima April 22, 2024, 7:47 p.m. UTC 
ioctl(SIOCGARP) holds rtnl_lock() for __dev_get_by_name() and
later calls neigh_lookup(), which calls rcu_read_lock().

Let's extend the RCU section and replace __dev_get_by_name()
with dev_get_by_name_rcu() to avoid locking rtnl_lock().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/ipv4/arp.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)
diff mbox series

Patch

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 057aa23bf439..33cfa8c90445 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1003,11 +1003,15 @@  static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
  *	User level interface (ioctl)
  */
 
-static struct net_device *arp_req_dev_by_name(struct net *net, struct arpreq *r)
+static struct net_device *arp_req_dev_by_name(struct net *net, struct arpreq *r,
+					      bool getarp)
 {
 	struct net_device *dev;
 
-	dev = __dev_get_by_name(net, r->arp_dev);
+	if (getarp)
+		dev = dev_get_by_name_rcu(net, r->arp_dev);
+	else
+		dev = __dev_get_by_name(net, r->arp_dev);
 	if (!dev)
 		return ERR_PTR(-ENODEV);
 
@@ -1028,7 +1032,7 @@  static struct net_device *arp_req_dev(struct net *net, struct arpreq *r)
 	__be32 ip;
 
 	if (r->arp_dev[0])
-		return arp_req_dev_by_name(net, r);
+		return arp_req_dev_by_name(net, r, false);
 
 	if (r->arp_flags & ATF_PUBL)
 		return NULL;
@@ -1166,7 +1170,7 @@  static int arp_req_get(struct net *net, struct arpreq *r)
 	if (!r->arp_dev[0])
 		return -ENODEV;
 
-	dev = arp_req_dev_by_name(net, r);
+	dev = arp_req_dev_by_name(net, r, true);
 	if (IS_ERR(dev))
 		return PTR_ERR(dev);
 
@@ -1287,23 +1291,27 @@  int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
 	else if (*netmask && *netmask != htonl(0xFFFFFFFFUL))
 		return -EINVAL;
 
-	rtnl_lock();
-
 	switch (cmd) {
 	case SIOCDARP:
+		rtnl_lock();
 		err = arp_req_delete(net, &r);
+		rtnl_unlock();
 		break;
 	case SIOCSARP:
+		rtnl_lock();
 		err = arp_req_set(net, &r);
+		rtnl_unlock();
 		break;
 	case SIOCGARP:
+		rcu_read_lock();
 		err = arp_req_get(net, &r);
+		rcu_read_unlock();
+
+		if (!err && copy_to_user(arg, &r, sizeof(r)))
+			err = -EFAULT;
 		break;
 	}
 
-	rtnl_unlock();
-	if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
-		err = -EFAULT;
 	return err;
 }