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 504C2481247; Tue, 25 Aug 2026 13:57:50 +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=1787666271; cv=none; b=T3kjWf7F9OOTeRKwLR2/mvWPhI9OTI11kPxxC0YYLgersRCcZ6Ds38rLLVWTXZHBOG7fUmwvmWw2MNeYhu7dG6KIRy78eQqm32PsUQohqwTDw02FLokT75cPQx3rkpd/BPxeNZzv4onkoU3chHwU+nNi6CcdICAp6jFhQ6OLmsI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787666271; c=relaxed/simple; bh=tMsuZb+Fti/E5AKUb7pGf2TSdd+amEcVPAdNmHzvQAE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Y9G3bi1Y/XTueWrqW7WpvWpRucF8SxnPMYJaKjyOuqxIPySw8OCA9vjsS5NHV3f4GA6D0UDisJs7HvlAOR5LB7FAvrwGetcrt/UY5Du6Zkx/m4K4epddPSmRI4G7h/yKQFpjTTiRvW0wK3UWSjuflAUs5vSU4gqzKtjPStF7iO8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=guuubVE1; 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="guuubVE1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AD0D81F000E9; Tue, 25 Aug 2026 13:57:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787666270; bh=AS99pU/oPKzRqt0QdL/HmY08su6EmK1J6qQsW95K2MA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=guuubVE1yBvaELI13woO0fsfJdgmhOb+8rcIyJIfYGoTKAdIodSDEHVJZfzPUsccY j4x8dLd2bA/awr8fl6/7Xv4WqP9iK6e+Rbf2lFfWpZfa6km45iSjmzmrPRri6qSSiD YQdvc0TdcasTO7HmXNYA8XQ8bk34pdRGCuOr+oDc= 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 5.15 62/76] xfrm: fix sk_dst_cache double-free in xfrm_user_policy() Date: Tue, 25 Aug 2026 15:26:55 +0200 Message-ID: <20260825132544.008422329@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260825132541.568214149@linuxfoundation.org> References: <20260825132541.568214149@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 5.15-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 8a75c91a02b4e..7180d4810d339 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -2430,7 +2430,7 @@ 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; } @@ -2470,7 +2470,7 @@ 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