diff mbox series

[net-next,4/8] net: write once on dev->allmulti and dev->promiscuity

Message ID 20240503192059.3884225-5-edumazet@google.com (mailing list archive)
State Accepted
Commit 55a2c86c8db3d7aa2c1967efd37ed47d5ae37f43
Delegated to: Netdev Maintainers
Headers show
Series rtnetlink: more rcu conversions for rtnl_fill_ifinfo() | 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: 933 this patch: 933
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 4 of 4 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: 944 this patch: 944
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 72 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 79 this patch: 79
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-05-05--03-00 (tests: 1003)

Commit Message

Eric Dumazet May 3, 2024, 7:20 p.m. UTC 
In the following patch we want to read dev->allmulti
and dev->promiscuity locklessly from rtnl_fill_ifinfo()

In this patch I change __dev_set_promiscuity() and
__dev_set_allmulti() to write these fields (and dev->flags)
only if they succeed, with WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/dev.c | 36 ++++++++++++++++++++----------------
 1 file changed, 20 insertions(+), 16 deletions(-)

Comments

Simon Horman May 5, 2024, 2:54 p.m. UTC | #1 
On Fri, May 03, 2024 at 07:20:55PM +0000, Eric Dumazet wrote:
> In the following patch we want to read dev->allmulti
> and dev->promiscuity locklessly from rtnl_fill_ifinfo()
> 
> In this patch I change __dev_set_promiscuity() and
> __dev_set_allmulti() to write these fields (and dev->flags)
> only if they succeed, with WRITE_ONCE() annotations.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>

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

Patch

diff --git a/net/core/dev.c b/net/core/dev.c
index 9c8c2ab2d76c3587d9114bc86a395341e1fd4d2b..35ce603ffc57fa209dc9a57e60981a2bca5e6a29 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8544,27 +8544,29 @@  static void dev_change_rx_flags(struct net_device *dev, int flags)
 static int __dev_set_promiscuity(struct net_device *dev, int inc, bool notify)
 {
 	unsigned int old_flags = dev->flags;
+	unsigned int promiscuity, flags;
 	kuid_t uid;
 	kgid_t gid;
 
 	ASSERT_RTNL();
 
-	dev->flags |= IFF_PROMISC;
-	dev->promiscuity += inc;
-	if (dev->promiscuity == 0) {
+	promiscuity = dev->promiscuity + inc;
+	if (promiscuity == 0) {
 		/*
 		 * Avoid overflow.
 		 * If inc causes overflow, untouch promisc and return error.
 		 */
-		if (inc < 0)
-			dev->flags &= ~IFF_PROMISC;
-		else {
-			dev->promiscuity -= inc;
+		if (unlikely(inc > 0)) {
 			netdev_warn(dev, "promiscuity touches roof, set promiscuity failed. promiscuity feature of device might be broken.\n");
 			return -EOVERFLOW;
 		}
+		flags = old_flags & ~IFF_PROMISC;
+	} else {
+		flags = old_flags | IFF_PROMISC;
 	}
-	if (dev->flags != old_flags) {
+	WRITE_ONCE(dev->promiscuity, promiscuity);
+	if (flags != old_flags) {
+		WRITE_ONCE(dev->flags, flags);
 		netdev_info(dev, "%s promiscuous mode\n",
 			    dev->flags & IFF_PROMISC ? "entered" : "left");
 		if (audit_enabled) {
@@ -8615,25 +8617,27 @@  EXPORT_SYMBOL(dev_set_promiscuity);
 static int __dev_set_allmulti(struct net_device *dev, int inc, bool notify)
 {
 	unsigned int old_flags = dev->flags, old_gflags = dev->gflags;
+	unsigned int allmulti, flags;
 
 	ASSERT_RTNL();
 
-	dev->flags |= IFF_ALLMULTI;
-	dev->allmulti += inc;
-	if (dev->allmulti == 0) {
+	allmulti = dev->allmulti + inc;
+	if (allmulti == 0) {
 		/*
 		 * Avoid overflow.
 		 * If inc causes overflow, untouch allmulti and return error.
 		 */
-		if (inc < 0)
-			dev->flags &= ~IFF_ALLMULTI;
-		else {
-			dev->allmulti -= inc;
+		if (unlikely(inc > 0)) {
 			netdev_warn(dev, "allmulti touches roof, set allmulti failed. allmulti feature of device might be broken.\n");
 			return -EOVERFLOW;
 		}
+		flags = old_flags & ~IFF_ALLMULTI;
+	} else {
+		flags = old_flags | IFF_ALLMULTI;
 	}
-	if (dev->flags ^ old_flags) {
+	WRITE_ONCE(dev->allmulti, allmulti);
+	if (flags != old_flags) {
+		WRITE_ONCE(dev->flags, flags);
 		netdev_info(dev, "%s allmulticast mode\n",
 			    dev->flags & IFF_ALLMULTI ? "entered" : "left");
 		dev_change_rx_flags(dev, IFF_ALLMULTI);