diff mbox series

[net,v3,1/2] net: ipv6: fix dst ref loop on input in seg6 lwt

Message ID 20250225175139.25239-2-justin.iurman@uliege.be (mailing list archive)
State New
Delegated to: Netdev Maintainers
Headers show
Series fixes for seg6 and rpl lwtunnels on input | 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: 0 this patch: 0
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 6 of 7 maintainers
netdev/build_clang success Errors and warnings before: 0 this patch: 0
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: 2 this patch: 2
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 29 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 pending net-next-2025-02-25--21-00 (tests: 0)

Commit Message

Justin Iurman Feb. 25, 2025, 5:51 p.m. UTC 
Prevent a dst ref loop on input in seg6_iptunnel.

Fixes: af4a2209b134 ("ipv6: sr: use dst_cache in seg6_input")
Cc: David Lebrun <dlebrun@google.com>
Cc: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Justin Iurman <justin.iurman@uliege.be>
---
 net/ipv6/seg6_iptunnel.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c
index 33833b2064c0..51583461ae29 100644
--- a/net/ipv6/seg6_iptunnel.c
+++ b/net/ipv6/seg6_iptunnel.c
@@ -472,10 +472,18 @@  static int seg6_input_core(struct net *net, struct sock *sk,
 {
 	struct dst_entry *orig_dst = skb_dst(skb);
 	struct dst_entry *dst = NULL;
+	struct lwtunnel_state *lwtst;
 	struct seg6_lwt *slwt;
 	int err;
 
-	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
+	/* We cannot dereference "orig_dst" once ip6_route_input() or
+	 * skb_dst_drop() is called. However, in order to detect a dst loop, we
+	 * need the address of its lwtstate. So, save the address of lwtstate
+	 * now and use it later as a comparison.
+	 */
+	lwtst = orig_dst->lwtstate;
+
+	slwt = seg6_lwt_lwtunnel(lwtst);
 
 	local_bh_disable();
 	dst = dst_cache_get(&slwt->cache);
@@ -490,7 +498,9 @@  static int seg6_input_core(struct net *net, struct sock *sk,
 	if (!dst) {
 		ip6_route_input(skb);
 		dst = skb_dst(skb);
-		if (!dst->error) {
+
+		/* cache only if we don't create a dst reference loop */
+		if (!dst->error && lwtst != dst->lwtstate) {
 			local_bh_disable();
 			dst_cache_set_ip6(&slwt->cache, dst,
 					  &ipv6_hdr(skb)->saddr);