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[v3,net,13/16] ipv6: use RCU protection in ip6_default_advmss()

Message ID 20250204132357.102354-14-edumazet@google.com (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series net: first round to use dev_net_rcu() | expand

Checks

Context Check Description
netdev/series_format fail Series longer than 15 patches
netdev/tree_selection success Clearly marked for net, async
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers warning 1 maintainers not CCed: dsahern@kernel.org
netdev/build_clang success Errors and warnings before: 2 this patch: 2
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: 1 this patch: 1
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 19 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 fail net-next-2025-02-04--18-00 (tests: 882)

Commit Message

Eric Dumazet Feb. 4, 2025, 1:23 p.m. UTC 
ip6_default_advmss() needs rcu protection to make
sure the net structure it reads does not disappear.

Fixes: 5578689a4e3c ("[NETNS][IPV6] route6 - make route6 per namespace")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/ipv6/route.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
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Patch

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 78362822b9070df138a0724dc76003b63026f9e2..ef2d23a1e3d532f5db37ca94ca482c5522dddffc 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3196,13 +3196,18 @@  static unsigned int ip6_default_advmss(const struct dst_entry *dst)
 {
 	struct net_device *dev = dst->dev;
 	unsigned int mtu = dst_mtu(dst);
-	struct net *net = dev_net(dev);
+	struct net *net;
 
 	mtu -= sizeof(struct ipv6hdr) + sizeof(struct tcphdr);
 
+	rcu_read_lock();
+
+	net = dev_net_rcu(dev);
 	if (mtu < net->ipv6.sysctl.ip6_rt_min_advmss)
 		mtu = net->ipv6.sysctl.ip6_rt_min_advmss;
 
+	rcu_read_unlock();
+
 	/*
 	 * Maximal non-jumbo IPv6 payload is IPV6_MAXPLEN and
 	 * corresponding MSS is IPV6_MAXPLEN - tcp_header_size.