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 0DD28347517; Wed, 8 Apr 2026 18:08:55 +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=1775671735; cv=none; b=IfZo0IDgr8iL8zoo1qnpQwxnCPPz7m8NuHGFvt5nYdVJsaMcejgd+79Pc/OggYVVKZU+KomfDZ8HUjS5DXVNxJKX7mQTC6xFoLRxWMbIfhfO8wzzl5RZnEYF9hrSM1HAVm/l6olroTLtS8StJuNGZUjlDHD6kUwOpLKQWNjP+z4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775671735; c=relaxed/simple; bh=JVD1PV65oX/R8f7rUnyO8MrzdV6XgWC6cq33JvXQm+k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=J2Qx+lOfZD+tWd19VgcwOTbzmBALUYEf/RpXc5ZlOwPCQmDS+OoJbbW1PHnnVZLusUKkfGU5R1HEW+MdJ/8NTitcbH4+C+W0A55jm/J7Vsm0LxRGiYT/ojTT/E0NygJlDro5uLBKGS0hwya7wg+1QqFtjtUV5CQyKgRuiCmplCA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Y8A43J3v; 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="Y8A43J3v" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96A1DC19421; Wed, 8 Apr 2026 18:08:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775671734; bh=JVD1PV65oX/R8f7rUnyO8MrzdV6XgWC6cq33JvXQm+k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Y8A43J3vaOnH+TlST/Pi443TsL6O6lVyr7ckXT7LWJNYn+QkN6FUzWJbmZs5EmW9O wUKeVqWTLQbP+6cG2tIdqijgmFkxMFv09KOMc3B0sdxQw0Ap8iYrqUY2icgf32q9OQ XqXh7VhKtEH/VZ75hiQdZAsqfUKwfwiTaOOQJBjA= 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 6.1 046/312] net: fix fanout UAF in packet_release() via NETDEV_UP race Date: Wed, 8 Apr 2026 19:59:23 +0200 Message-ID: <20260408175935.455372441@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175933.715315542@linuxfoundation.org> References: <20260408175933.715315542@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 6.1-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 8c06e3e6b52b5..502d2f6de18a2 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3185,6 +3185,7 @@ 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