[PATCH v2 net-next 1/4] net: synchronize proc_do_rss_key() with netdev_rss_key_fill()
From: Eric Dumazet <edumazet@google.com>
Date: 2026-09-22 16:35:01
Subsystem:
networking [ethtool], networking [general], the rest · Maintainers:
Andrew Lunn, Jakub Kicinski, "David S. Miller", Eric Dumazet, Paolo Abeni, Linus Torvalds
proc_do_rss_key() reads netdev_rss_key[] without synchronization, so a
concurrent reader of /proc/sys/net/core/netdev_rss_key can observe a
partially populated key while netdev_rss_key_fill() is initializing it.
Publish a boolean flag after an smp_wmb() once netdev_rss_key_fill() has
populated netdev_rss_key[], and pair it with an smp_rmb() in
proc_do_rss_key(), printing zero bytes until the flag is set.
Fixes: 960fb622f851 ("net: provide a per host RSS key generic infrastructure")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/core/dev.h | 1 +
net/core/sysctl_net_core.c | 7 ++++++-
net/ethtool/ioctl.c | 7 +++++++
3 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/net/core/dev.h b/net/core/dev.h
index b757faead4d1a3e445e54d2f468c38c9e09b6762..0127b4d03e5251e0ad695aa649d0c52c2248bc8c 100644
--- a/net/core/dev.h
+++ b/net/core/dev.h@@ -95,6 +95,7 @@ extern int netdev_unregister_timeout_secs; extern int weight_p; extern int dev_weight_rx_bias; extern int dev_weight_tx_bias; +extern bool netdev_rss_key_initialized; extern struct rw_semaphore dev_addr_sem;
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 23310581f494553e3ad8c4e010c7799e04f976c0..473c162736d6928d13d22e9902262a43705196d9 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c@@ -337,10 +337,15 @@ static int proc_do_rss_key(const struct ctl_table *table, int write, { char buf[NETDEV_RSS_KEY_LEN * 3]; struct ctl_table fake_table; + bool initialized; char *pos = buf; + initialized = READ_ONCE(netdev_rss_key_initialized); + /* Pair with smp_wmb() in netdev_rss_key_fill(). */ + smp_rmb(); + for (int i = 0; i < NETDEV_RSS_KEY_LEN; i++) { - pos = hex_byte_pack(pos, netdev_rss_key[i]); + pos = hex_byte_pack(pos, initialized ? netdev_rss_key[i] : 0); *pos++ = ':'; } *(--pos) = 0;
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 4b0bc503f9307880e436d5ee30f75476264a0c6b..b2820f02ca2790a8a3c13395e20040ee6976006f 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c@@ -34,6 +34,7 @@ #include <net/netdev_lock.h> #include <net/netdev_queues.h> +#include "../core/dev.h" #include "common.h" /* State held across locks and calls for commands which have devlink fallback */
@@ -1302,11 +1303,17 @@ static int ethtool_copy_validate_indir(u32 *indir, void __user *useraddr, } u8 netdev_rss_key[NETDEV_RSS_KEY_LEN] __read_mostly; +bool netdev_rss_key_initialized __read_mostly; void netdev_rss_key_fill(void *buffer, size_t len) { BUG_ON(len > sizeof(netdev_rss_key)); net_get_random_once(netdev_rss_key, sizeof(netdev_rss_key)); + if (unlikely(!READ_ONCE(netdev_rss_key_initialized))) { + /* Pair with smp_rmb() in proc_do_rss_key(). */ + smp_wmb(); + WRITE_ONCE(netdev_rss_key_initialized, true); + } memcpy(buffer, netdev_rss_key, len); } EXPORT_SYMBOL(netdev_rss_key_fill);
--
2.55.0.1082.g2b9226bbc0-goog