diff mbox series

[net,3/5] ipv6: sr: block BH in seg6_output_core() and seg6_input_core()

Message ID 20240531132636.2637995-4-edumazet@google.com (mailing list archive)
State Accepted
Commit c0b98ac1cc104f48763cdb27b1e9ac25fd81fc90
Delegated to: Netdev Maintainers
Headers show
Series dst_cache: fix possible races | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net
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: 904 this patch: 904
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: 906 this patch: 906
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: 908 this patch: 908
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 47 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-2024-06-03--15-00 (tests: 1041)

Commit Message

Eric Dumazet May 31, 2024, 1:26 p.m. UTC 
As explained in commit 1378817486d6 ("tipc: block BH
before using dst_cache"), net/core/dst_cache.c
helpers need to be called with BH disabled.

Disabling preemption in seg6_output_core() is not good enough,
because seg6_output_core() is called from process context,
lwtunnel_output() only uses rcu_read_lock().

We might be interrupted by a softirq, re-enter seg6_output_core()
and corrupt dst_cache data structures.

Fix the race by using local_bh_disable() instead of
preempt_disable().

Apply a similar change in seg6_input_core().

Fixes: fa79581ea66c ("ipv6: sr: fix several BUGs when preemption is enabled")
Fixes: 6c8702c60b88 ("ipv6: sr: add support for SRH encapsulation and injection with lwtunnels")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: David Lebrun <dlebrun@google.com>
---
 net/ipv6/seg6_iptunnel.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)
diff mbox series

Patch

diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c
index a75df2ec8db0d369a4e3481576fc09f511a4dd36..098632adc9b5afa69e4b65439ee54c3fc0a8d668 100644
--- a/net/ipv6/seg6_iptunnel.c
+++ b/net/ipv6/seg6_iptunnel.c
@@ -464,23 +464,21 @@  static int seg6_input_core(struct net *net, struct sock *sk,
 
 	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
 
-	preempt_disable();
+	local_bh_disable();
 	dst = dst_cache_get(&slwt->cache);
-	preempt_enable();
 
 	if (!dst) {
 		ip6_route_input(skb);
 		dst = skb_dst(skb);
 		if (!dst->error) {
-			preempt_disable();
 			dst_cache_set_ip6(&slwt->cache, dst,
 					  &ipv6_hdr(skb)->saddr);
-			preempt_enable();
 		}
 	} else {
 		skb_dst_drop(skb);
 		skb_dst_set(skb, dst);
 	}
+	local_bh_enable();
 
 	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 	if (unlikely(err))
@@ -536,9 +534,9 @@  static int seg6_output_core(struct net *net, struct sock *sk,
 
 	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
 
-	preempt_disable();
+	local_bh_disable();
 	dst = dst_cache_get(&slwt->cache);
-	preempt_enable();
+	local_bh_enable();
 
 	if (unlikely(!dst)) {
 		struct ipv6hdr *hdr = ipv6_hdr(skb);
@@ -558,9 +556,9 @@  static int seg6_output_core(struct net *net, struct sock *sk,
 			goto drop;
 		}
 
-		preempt_disable();
+		local_bh_disable();
 		dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
-		preempt_enable();
+		local_bh_enable();
 	}
 
 	skb_dst_drop(skb);