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 E06CF313298; Mon, 13 Apr 2026 16:53:52 +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=1776099233; cv=none; b=s8kJb8MNncLkuduig9E2QKP8HOHBu3BQij8CBncw0qAnV0MPdU0nHPcrIz2DOd+5eOgL1yVNZ6d4QBoVG1WbuUU2jGdv1L4iz5KHu3ddy1HILXjZFtc9h8jL9qbdcX4XjZigrqoqiQN7lKcVzbJEcTrA++IJKDfM/VjZVV0vDAs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776099233; c=relaxed/simple; bh=NR4LPa8wsXRiBMX5lDBNwjp2uoP6m4Kphfdz0eHo0d8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DjoR2qviZYZaDvP0eCYSrCd8bF15njXcpdg4UrGKvu32HsRYJqyRXo6K1038CaJAqcgg2EAOmYBqFQc9wt7S9wFssNEwsW0iUdr3dwXGLDutsXzMow2wkVLDqNPOE6nI2xrs2YbhD5+6XpWVyCCyJ1z8tppJ3O6WIAcT3OKSXow= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=dQJwuf7R; 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="dQJwuf7R" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7123DC2BCAF; Mon, 13 Apr 2026 16:53:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1776099232; bh=NR4LPa8wsXRiBMX5lDBNwjp2uoP6m4Kphfdz0eHo0d8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dQJwuf7Rv6ofL7uOpf0N0nk15p0ouxB2oyj7saUGPvHEPd8fwUwLKhHbYQ4vg9EUT s3UWCgTt2NTcaRX8oUkfWvScUn/UVc6E4tsRG5E9d6knofHFifMnd9o8oxKbR1S5IV ZfOXolQ8Pl4Ns3BvxZycWBgrHC8jdKGRQOOOyh98= 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 5.10 262/491] net: fix fanout UAF in packet_release() via NETDEV_UP race Date: Mon, 13 Apr 2026 17:58:27 +0200 Message-ID: <20260413155828.860810780@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260413155819.042779211@linuxfoundation.org> References: <20260413155819.042779211@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 5.10-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 4614fae54ed7f..1c9b2d67c3ed4 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3147,6 +3147,7 @@ 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