From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 798E942E426; Tue, 25 Aug 2026 13:41:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787665315; cv=none; b=JP8CX8v3NeQiZLrv7cs3H+4cW/M4XmOzjKg+U1sopvMxrKRUUiA4F4jvf/tLfzy+4MzdIKcY606RB5qfDKII4FrRzthQ936/JgG2ttCsMrQ6Lx1YznMG+A7n/R4Ny+C4r/vgasjYiDKTyJO+TVCecco+7nNzIBiCavbe7+AGNSE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787665315; c=relaxed/simple; bh=Er4Lcrog1YN3DUaU86ht2BxA9kDzq+P1bqibqmOZRAI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WG/IJ00fyEWlrOazOz5EFibH8msXoM/l2HD53EKBjWNHXeMpVXoNKMFSsgKrGsuTJVXZcItzKsS0gXpoyjJ/eiaRTm9yxZ7mP4W42xR3mQJC5xVvlqkLV954Y1vCGN6h5ppdVRL9xxHNbRr3zXPFLur8WTnqQoLVl8i+LwPGZ/Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=YiSt0GQK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="YiSt0GQK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D1E0F1F000E9; Tue, 25 Aug 2026 13:41:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787665314; bh=O+90FlvgsUTBHGPQhOmtql++xFSj002vzxLHTzNt5uQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=YiSt0GQKlzcLy1rFhOufVc0PIiS1KoTRYpoy5/K/Lajff5LVhezHT/CwyvB8w8UGg b1meq1+iNaaZa8YsUJSKIpY3CjsnWK7sINem18D4yUq7hNsw55pHBBXzIlnrYLob3e fl8M4l5A8QyxQis2PABjd9YVDQDhdoublVZiiwEE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, AutonomousCodeSecurity@microsoft.com, "Xiang Mei (Microsoft)" , Steffen Klassert , Sasha Levin Subject: [PATCH 6.18 72/94] xfrm: fix sk_dst_cache double-free in xfrm_user_policy() Date: Tue, 25 Aug 2026 15:26:08 +0200 Message-ID: <20260825132544.702318552@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260825132541.887883084@linuxfoundation.org> References: <20260825132541.887883084@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Xiang Mei (Microsoft) [ Upstream commit c283e9ada7fcb7dd4b10592623086b2e6d2f9925 ] xfrm_user_policy() clears the socket dst cache with __sk_dst_reset(), i.e. the non-atomic __sk_dst_set(sk, NULL): it reads sk_dst_cache with rcu_dereference_protected(), stores NULL and dst_release()s the old dst. That is only safe if no other thread modifies sk_dst_cache concurrently. For a connected UDP socket that does not hold: the transmit fast path (udp_sendmsg -> sk_dst_check -> sk_dst_reset) resets the cache locklessly with an atomic xchg(). A per-socket policy change racing a send can make both sides observe the same old dst and each dst_release() it, dropping the socket's single reference twice and freeing the xfrm_dst bundle while it is still referenced: BUG: KASAN: slab-use-after-free in dst_release Write of size 4 at addr ffff88801897b6c0 by task exploit/155 Call Trace: ... dst_release (... ./include/linux/rcuref.h:109) xfrm_user_policy (./include/net/sock.h:2239 ./include/net/sock.h:2256 net/xfrm/xfrm_state.c:3053) do_ip_setsockopt (net/ipv4/ip_sockglue.c:1347) ip_setsockopt (net/ipv4/ip_sockglue.c:1417) do_sock_setsockopt (net/socket.c:2368) __sys_setsockopt (net/socket.c:2393) __x64_sys_setsockopt (net/socket.c:2396) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Reachable by an unprivileged user via a user+network namespace. Use the atomic sk_dst_reset() so the cache is cleared and released with a single xchg(): whichever side wins releases the dst once, the other sees NULL and does nothing. Behaviour is otherwise unchanged. Fixes: 2b06cdf3e688 ("xfrm: Clear sk_dst_cache when applying per-socket policy.") Fixes: be8f8284cd89 ("net: xfrm: allow clearing socket xfrm policies.") Reported-by: AutonomousCodeSecurity@microsoft.com Signed-off-by: Xiang Mei (Microsoft) Signed-off-by: Steffen Klassert Signed-off-by: Sasha Levin --- net/xfrm/xfrm_state.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index b9049c2297bd5..f463c7bd5321d 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -2975,7 +2975,7 @@ int xfrm_user_policy(struct sock *sk, int optname, sockptr_t optval, int optlen) if (sockptr_is_null(optval) && !optlen) { xfrm_sk_policy_insert(sk, XFRM_POLICY_IN, NULL); xfrm_sk_policy_insert(sk, XFRM_POLICY_OUT, NULL); - __sk_dst_reset(sk); + sk_dst_reset(sk); return 0; } @@ -3015,7 +3015,7 @@ int xfrm_user_policy(struct sock *sk, int optname, sockptr_t optval, int optlen) if (err >= 0) { xfrm_sk_policy_insert(sk, err, pol); xfrm_pol_put(pol); - __sk_dst_reset(sk); + sk_dst_reset(sk); err = 0; } -- 2.53.0