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 3E199157A5A; Wed, 30 Sep 2026 15:57:19 +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=1790783842; cv=none; b=Gab8aEqOsZYkvsoXvA1im9uvng79y5X7yRoYTc+V5IG0IJvspKE2syb0I8UksYptRrAw8Eiy38sJY8jiSNRlwkHDD26lv5GBritFlmPwRRKhMr/gtP8QpyqUfX8hz3s9zxL4HpTCJilnuX/HGSileVF7zVRuKd7SusjCZTZw3FA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790783842; c=relaxed/simple; bh=uSf00G4APLbyhtLFhh7U6pLwUnypiyVrEnic90WDgWs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PtLPNnW9+sG2O/ivLlpubw/aZYUyrORV+hRKIrZtkvAkvhNfVmvvm/xoJMiw0bKfYMVa2kfV/Ws6vUTt8BskTW7CofCvp4IJpHObrKPqn2mbrNY1knwKpJowTWdKXcF8VLh6drUGNLBZk8QvxzL6ek0Rlbd/aF/lUyY11ggd/ds= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=tIoYrCXM; 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="tIoYrCXM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C68521F00898; Wed, 30 Sep 2026 15:57:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790783838; bh=2pY+lDuPmhghb34j90Gvwk2/XaobvpKQOOiu6rpC9ho=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=tIoYrCXMD8dxQrU7TmRJln4INBAiiku5fAzKawGyfwWvflt+CZg9ZQ12m8bsUdF4D S9Egn2weXbe53bSpOnPzpkzRGWmphpX/8//oSyvN+UV5q88KqLPL/oh2YZu1TADR+V 7xwRnsqNtnFnuHawd9ivioMbMMHVIEd7Uge8HwEQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sanghyun Park , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.10 538/595] vxlan: use one headroom snapshot for neighbour replies Date: Wed, 30 Sep 2026 17:27:11 +0200 Message-ID: <20260930152359.279404394@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152347.700140858@linuxfoundation.org> References: <20260930152347.700140858@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: Sanghyun Park [ Upstream commit 481506a756dcd828ef42391cb08f38d8d96d38fc ] vxlan_na_create() samples LL_RESERVED_SPACE() to size the reply skb and then samples it again to reserve headroom. A concurrent vxlan_changelink() can update needed_headroom between the two reads, creating a TOCTOU race. The second value can exceed the allocation and make the Ethernet header write out of bounds. The race is reproducible on the unpatched kernel. It occurred when vxlan_na_create() generated a neighbour reply while vxlan_changelink() changed the link headroom. KASAN caught a four-byte write two bytes beyond a 704-byte skbuff_small_head allocation. Snapshot the headroom once and use that value for both allocation and reservation. Fixes: 4b29dba9c085 ("vxlan: fix nonfunctional neigh_reduce()") Signed-off-by: Sanghyun Park Link: https://patch.msgid.link/20260918032842.502409-2-sanghyun.park.cnu@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/vxlan/vxlan_core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c index a2955729998cd..ac45cf9eea836 100644 --- a/drivers/net/vxlan/vxlan_core.c +++ b/drivers/net/vxlan/vxlan_core.c @@ -2085,13 +2085,15 @@ static struct sk_buff *vxlan_na_create(struct sk_buff *request, struct ipv6hdr *pip6; u8 *daddr; int na_olen = 8; /* opt hdr + ETH_ALEN for target */ + int headroom; int ns_olen; int i, len; if (dev == NULL || !pskb_may_pull(request, request->len)) return NULL; - len = LL_RESERVED_SPACE(dev) + sizeof(struct ipv6hdr) + + headroom = LL_RESERVED_SPACE(dev); + len = headroom + sizeof(struct ipv6hdr) + sizeof(*na) + na_olen + dev->needed_tailroom; reply = alloc_skb(len, GFP_ATOMIC); if (reply == NULL) @@ -2099,7 +2101,7 @@ static struct sk_buff *vxlan_na_create(struct sk_buff *request, reply->protocol = htons(ETH_P_IPV6); reply->dev = dev; - skb_reserve(reply, LL_RESERVED_SPACE(request->dev)); + skb_reserve(reply, headroom); skb_push(reply, sizeof(struct ethhdr)); skb_reset_mac_header(reply); -- 2.53.0