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 03788517BAF; Wed, 30 Sep 2026 17:28:31 +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=1790789314; cv=none; b=cmoCpGC1ypmmeKcSXuZZ4gJFWOqZpaLsCUy9HUkUOlVgu/asEaK0pXGhcFHlGFsqxyptYG27Fyb/Htny0wyFTirRjHQ6tRF7e2xlg8IDuQURqeU3lLppG903UFyoDA4Nia2pMuNyow9Yh3niqj0zRCt+//er1ep10tbIDRyzZrU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790789314; c=relaxed/simple; bh=NsAVlu/X4rjX5TIiWgAqCVYW3e1BuY/UOl8Q9w2zQ5E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=m2Lz3tX/ikndDnZ5pdlNRpdLHgjvOVfctyJAagRod7CVSjycREcfyefkchdjr7M6opQuzEZfwylvCRVZwwfFkpHYvUaCjk8QSihVfw5/NheeKkr6NjVb/zQDoVNUA/gPkGvZOZZeOkAb2E5I5O0II5qa32hNI9NEGE7I1JLJzUo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=IiTEriuZ; 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="IiTEriuZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A58601F00898; Wed, 30 Sep 2026 17:28:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790789309; bh=S5pfhfJxE3kPIs4jXwRCKCowySLgNAeYnRLDbwBLB5A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=IiTEriuZP1pduj3Hx6ijkvh40PEIKFY7PurNF2/QzDdRXUKl9HzLw9KQEHL0HzKt0 0LMmaxtW2cYPZ1qrWrt5yZGnn6YbxbjZQF1JXJpJzZiEEWpOtNk36qilFDoYx33PNI 3lFvl/T7IDb80y0GXemLWNWBsZewaLUnwu7MZ5bk= 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 6.12 431/877] vxlan: use one headroom snapshot for neighbour replies Date: Wed, 30 Sep 2026 17:22:22 +0200 Message-ID: <20260930152423.987564048@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152414.738996857@linuxfoundation.org> References: <20260930152414.738996857@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 6.12-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 b14dbc6892078..f612def46c3c4 100644 --- a/drivers/net/vxlan/vxlan_core.c +++ b/drivers/net/vxlan/vxlan_core.c @@ -1979,13 +1979,15 @@ 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) @@ -1993,7 +1995,7 @@ 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