diff mbox series

[v2,net,04/16] ipv4: use RCU protection in ipv4_default_advmss()

Message ID 20250203143046.3029343-5-edumazet@google.com (mailing list archive)
State Superseded
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 fail 1 blamed authors not CCed: xu.xin16@zte.com.cn; 2 maintainers not CCed: xu.xin16@zte.com.cn 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: 0 this patch: 0
netdev/checkpatch warning CHECK: Alignment should match open parenthesis
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 warning net-next-2025-02-03--21-00 (tests: 81)

Commit Message

Eric Dumazet Feb. 3, 2025, 2:30 p.m. UTC 
ipv4_default_advmss() must use RCU protection to make
sure the net structure it reads does not disappear.

Fixes: 2e9589ff809e ("ipv4: Namespaceify min_adv_mss sysctl knob")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/ipv4/route.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 577b88a43293aa801c3ee736d7e5cc4d97917717..74c074f45758be5ae78a87edb31837481cc40278 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1307,10 +1307,15 @@  static void set_class_tag(struct rtable *rt, u32 tag)
 
 static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
 {
-	struct net *net = dev_net(dst->dev);
 	unsigned int header_size = sizeof(struct tcphdr) + sizeof(struct iphdr);
-	unsigned int advmss = max_t(unsigned int, ipv4_mtu(dst) - header_size,
-				    net->ipv4.ip_rt_min_advmss);
+	unsigned int advmss;
+	struct net *net;
+
+	rcu_read_lock();
+	net = dev_net_rcu(dst->dev);
+	advmss = max_t(unsigned int, ipv4_mtu(dst) - header_size,
+				   net->ipv4.ip_rt_min_advmss);
+	rcu_read_unlock();
 
 	return min(advmss, IPV4_MAX_PMTU - header_size);
 }