From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 C59F02DECDE; Tue, 31 Mar 2026 17:01:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774976479; cv=none; b=dZ8CnCy4F2gAlXhBsHt+Lkdb49qPlbHI45scFnHJpbFoMdM5pKmx5kxV2Eova2NU/ZBlQ2xrwzEdEcFTT227Q9Tg6sRhVNb3JYuioUr5KU8N62Vwz4urCKVm/siF18D5/dZe9u2SJI47LgmvnsENjrXtiHcIx18AvWDx8mPhKRI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774976479; c=relaxed/simple; bh=zD5OrftLh5YM8enw2ROeNXU96hd6NrJvm5VaNTGyMe0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZFFXXLCgo05PB0BiW3P+xZv2ANrgLIVKUIaSNU1Yefm/20F3329D+X/tmUwFlmNRCpdzbIYg1p39zzPhjY+l0ZbQ72xgmK55QidkRpbEYN1x3wE0pvcTeSYqUL6rOp5roYi14RbtZZO6mKQYvDf1UUoD2YUcTjBJgP4qn17zWoQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FpovHph6; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="FpovHph6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 45B11C19423; Tue, 31 Mar 2026 17:01:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774976479; bh=zD5OrftLh5YM8enw2ROeNXU96hd6NrJvm5VaNTGyMe0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FpovHph6Jf03G6+b1kg2jleEL8+0xOd/pxcXTh1/8SmtSbhfZf3DGdQ+j3vNxwX26 XRvTpYXv8/A25ga9NCcAhHCqBWxr1J3Wq3Q3sQQyeLFpd/G5X6A7KP/Ve3DH1U7yf3 5OUxTesWnGf5Ha2MBxPTKMAJzjetDx1udVMnMJmk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yochai Eisenrich , Willem de Bruijn , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18 109/309] net: fix fanout UAF in packet_release() via NETDEV_UP race Date: Tue, 31 Mar 2026 18:20:12 +0200 Message-ID: <20260331161757.498569713@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260331161753.468533260@linuxfoundation.org> References: <20260331161753.468533260@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org 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: Yochai Eisenrich [ Upstream commit 42156f93d123436f2a27c468f18c966b7e5db796 ] `packet_release()` has a race window where `NETDEV_UP` can re-register a socket into a fanout group's `arr[]` array. The re-registration is not cleaned up by `fanout_release()`, leaving a dangling pointer in the fanout array. `packet_release()` does NOT zero `po->num` in its `bind_lock` section. After releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex` still matches the bound device. A concurrent `packet_notifier(NETDEV_UP)` that already found the socket in `sklist` can re-register the hook. For fanout sockets, this re-registration calls `__fanout_link(sk, po)` which adds the socket back into `f->arr[]` and increments `f->num_members`, but does NOT increment `f->sk_ref`. The fix sets `po->num` to zero in `packet_release` while `bind_lock` is held to prevent NETDEV_UP from linking, preventing the race window. This bug was found following an additional audit with Claude Code based on CVE-2025-38617. Fixes: ce06b03e60fc ("packet: Add helpers to register/unregister ->prot_hook") Link: https://blog.calif.io/p/a-race-within-a-race-exploiting-cve Signed-off-by: Yochai Eisenrich Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260319200610.25101-1-echelonh@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/packet/af_packet.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 173e6edda08f8..5c08e0da0dff4 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3135,6 +3135,7 @@ static int packet_release(struct socket *sock) spin_lock(&po->bind_lock); unregister_prot_hook(sk, false); + WRITE_ONCE(po->num, 0); packet_cached_dev_reset(po); if (po->prot_hook.dev) { -- 2.51.0