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 EFBCA3EDE59; Tue, 12 May 2026 17:54:28 +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=1778608469; cv=none; b=u6RO3318HC7u4bOItpDiS2k8n8EZCCUnTS+nHCRsX6Ps5DuPuNWdVR6/XyBD1QdzuFrX3tYb6Z/wosyCgCHDv0tF/GWdcdndHPLsshlKEI6samHAI+o5IIDzPs7Wi4jL2Hg4s5oNFhX7dstSPQTBjRbG5YymePS6yAAdjgFpTb0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778608469; c=relaxed/simple; bh=bNe+ksNqocKvIOGKvf422lx8uIKBqcsGIqu56NPZwgg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BOY5Z9UZwWBDlh9b43Ge1WC8kFgTMF/OO8R0rrns/L7IlfaR1QxVNP/Gm256vWMrwVt3pDnp1FcOLnsi/VSxGqqfmDkLkKb8IlFZsE95GHpOse8l2lZNMCUUUN+ncjfraH1NZXr3L07oVS6nNyrkMBFXQNgmDjSaDM4Ldl1RU7I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=waualWhw; 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="waualWhw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 804FAC2BCB0; Tue, 12 May 2026 17:54:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778608468; bh=bNe+ksNqocKvIOGKvf422lx8uIKBqcsGIqu56NPZwgg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=waualWhwqtQ3H4ZzpoDZ3emmy2rywXVfvTCs4WAftOrom2u2RgeL2qoH4rL6/tDfS aG+XUShU+musr/ohDRWwEKcfYS5fduhATjeOpQAEZExlBzMquimA+zH3Pss64T0EfE 2f8w1dcZBBNrjrR5YXT83bQ3CA5Dz/72E8bx060c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kai Zen , Jakub Kicinski Subject: [PATCH 6.18 092/270] net: rtnetlink: zero ifla_vf_broadcast to avoid stack infoleak in rtnl_fill_vfinfo Date: Tue, 12 May 2026 19:38:13 +0200 Message-ID: <20260512173940.397160192@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260512173938.452574370@linuxfoundation.org> References: <20260512173938.452574370@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: Kai Zen commit 4b9e327991815e128ad3af75c3a04630a63ce3e0 upstream. rtnl_fill_vfinfo() declares struct ifla_vf_broadcast on the stack without initialisation: struct ifla_vf_broadcast vf_broadcast; The struct contains a single fixed 32-byte field: /* include/uapi/linux/if_link.h */ struct ifla_vf_broadcast { __u8 broadcast[32]; }; The function then copies dev->broadcast into it using dev->addr_len as the length: memcpy(vf_broadcast.broadcast, dev->broadcast, dev->addr_len); On Ethernet devices (the overwhelming majority of SR-IOV NICs) dev->addr_len is 6, so only the first 6 bytes of broadcast[] are written. The remaining 26 bytes retain whatever was previously on the kernel stack. The full struct is then handed to userspace via: nla_put(skb, IFLA_VF_BROADCAST, sizeof(vf_broadcast), &vf_broadcast) leaking up to 26 bytes of uninitialised kernel stack per VF per RTM_GETLINK request, repeatable. The other vf_* structs in the same function are explicitly zeroed for exactly this reason - see the memset() calls for ivi, vf_vlan_info, node_guid and port_guid a few lines above. vf_broadcast was simply missed when it was added. Reachability: any unprivileged local process can open AF_NETLINK / NETLINK_ROUTE without capabilities and send RTM_GETLINK with an IFLA_EXT_MASK attribute carrying RTEXT_FILTER_VF. The kernel walks each VF and emits IFLA_VF_BROADCAST, leaking 26 bytes of stack per VF per request. Stack residue at this call site can include return addresses and transient sensitive data; KASAN with stack instrumentation, or KMSAN, will flag the nla_put() when reproduced. Zero the on-stack struct before the partial memcpy, matching the existing pattern used for the other vf_* structs in the same function. Fixes: 75345f888f70 ("ipoib: show VF broadcast address") Cc: stable@vger.kernel.org Signed-off-by: Kai Zen Link: https://patch.msgid.link/3c506e8f936e52b57620269b55c348af05d413a2.1777557228.git.kai.aizen.dev@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/core/rtnetlink.c | 1 + 1 file changed, 1 insertion(+) --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -1566,6 +1566,7 @@ static noinline_for_stack int rtnl_fill_ port_guid.vf = ivi.vf; memcpy(vf_mac.mac, ivi.mac, sizeof(ivi.mac)); + memset(&vf_broadcast, 0, sizeof(vf_broadcast)); memcpy(vf_broadcast.broadcast, dev->broadcast, dev->addr_len); vf_vlan.vlan = ivi.vlan; vf_vlan.qos = ivi.qos;