From 7f2d76c9c03257c0782afef9d95321fa04096f60 Mon Sep 17 00:00:00 2001 From: Sanghyun Park Date: Tue, 2 Jun 2026 18:49:05 +0900 Subject: [PATCH] xfrm: policy: fix use-after-free on inexact bin in xfrm_policy_bysel_ctx() Fix the race by pruning the bin while still holding xfrm_policy_lock, before dropping it. Use __xfrm_policy_inexact_prune_bin() directly since the lock is already held. The wrapper xfrm_policy_inexact_prune_bin() becomes unused and is removed. Race: CPU0 (XFRM_MSG_DELPOLICY) CPU1 (XFRM_MSG_NEWSPDINFO) ========================== ========================== xfrm_policy_bysel_ctx(): spin_lock_bh(xfrm_policy_lock) bin = xfrm_policy_inexact_lookup() __xfrm_policy_unlink(pol) spin_unlock_bh(xfrm_policy_lock) xfrm_policy_kill(ret) // wide window, lock not held xfrm_hash_rebuild(): spin_lock_bh(xfrm_policy_lock) __xfrm_policy_inexact_flush(): kfree_rcu(bin) // bin freed spin_unlock_bh(xfrm_policy_lock) xfrm_policy_inexact_prune_bin(bin) // UAF: bin is freed Fixes: 6be3b0db6db8 ("xfrm: policy: add inexact policy search tree infrastructure") Signed-off-by: Sanghyun Park Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_policy.c | 13 ++----------- 1 file changed, 2 insertions(+), 11 deletions(-) diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index dd09d2063da2..959544425692 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -1156,15 +1156,6 @@ static void __xfrm_policy_inexact_prune_bin(struct xfrm_pol_inexact_bin *b, bool } } -static void xfrm_policy_inexact_prune_bin(struct xfrm_pol_inexact_bin *b) -{ - struct net *net = read_pnet(&b->k.net); - - spin_lock_bh(&net->xfrm.xfrm_policy_lock); - __xfrm_policy_inexact_prune_bin(b, false); - spin_unlock_bh(&net->xfrm.xfrm_policy_lock); -} - static void __xfrm_policy_inexact_flush(struct net *net) { struct xfrm_pol_inexact_bin *bin, *t; @@ -1707,12 +1698,12 @@ xfrm_policy_bysel_ctx(struct net *net, const struct xfrm_mark *mark, u32 if_id, } ret = pol; } + if (bin && delete) + __xfrm_policy_inexact_prune_bin(bin, false); spin_unlock_bh(&net->xfrm.xfrm_policy_lock); if (ret && delete) xfrm_policy_kill(ret); - if (bin && delete) - xfrm_policy_inexact_prune_bin(bin); return ret; } EXPORT_SYMBOL(xfrm_policy_bysel_ctx);