From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout-y-209.mailbox.org (mout-y-209.mailbox.org [91.198.250.237]) (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 169D23A8744; Wed, 8 Apr 2026 17:25:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.198.250.237 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775669145; cv=none; b=KUluTBqzxhaYV0QI9fR+cJNp7402YQ8XBQYhM4bAnxDQ0PlRyhTrIdmHKcEV850IDG/oCOvPt3qa3c+4FvvBKkrEQkip97zVaGsAlzrm6ABJfenMekpAvbJAL5fVO59HggMlxg9GxVAsqCvUw0yO+Jmuam4CfNExhU9xgQ4meQA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775669145; c=relaxed/simple; bh=ot1KVTZnXZcUxJIpol/i2ytidhgDKLb91yaFFYtzrSM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=rNnCCQU5KKOyoH8Diddwr56zIeAhs2/ybwOffx5xls63JxUb68S3YPuSoqvuEBNucguJ5wmSkuRVCBMYABskho4tyCmRwKXg3y9I3KjPJPDk7cMZJGtXNSawX/IwA6o6ueDu7j1yG6403eoouapM4z54EoY+84J4CRMzYncLGjg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mailbox.org; spf=pass smtp.mailfrom=mailbox.org; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b=JZxKBpxI; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b=gSwTV38M; arc=none smtp.client-ip=91.198.250.237 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mailbox.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mailbox.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b="JZxKBpxI"; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b="gSwTV38M" Received: from smtp202.mailbox.org (smtp202.mailbox.org [10.196.197.202]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-y-209.mailbox.org (Postfix) with ESMTPS id 4frVMV20WbzB11w; Wed, 8 Apr 2026 19:25:42 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1775669142; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=kT13ZUtTLZv4hnmBJjWl4jvqjMLTj/qnsK+u4sO+FDo=; b=JZxKBpxIYXw4GFSbXeNM2/dx0ZhyMwqV6Ew5swpwqq8AOCghVEEoP3OjZlw647ZqDn7COA EyN6nWtaKDFc8w/BNnwW07bDs/AIefvbEnLcKxLaBYRE3t8nzr8GvsukzKawcRb8DF46ro 1YX61AtEQhTSko0dbg6oKgl8o8dgbXwrSI84IaJUWH157TooMPfD02hJ5wMLZRZF85isTs uXsSQZc1v9NUAW4kDAV6M1ECL73j9uJnQRjsxCFEZve6LO/Szl0U4azdad8FnBe5uzHP6b GjCAxMgTlda7wwT12xrJQEK2HRQg/ir5qNMjhaDAt1l3eZZdYHBNflWG4tx0EQ== From: Mashiro Chen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1775669140; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=kT13ZUtTLZv4hnmBJjWl4jvqjMLTj/qnsK+u4sO+FDo=; b=gSwTV38MH9GJJJHzK18+KV42orqZJH2G27KvzVDh0Yenc0wICroJ/A9SpyAkZBjEvQkuhI hHqMygSUwIt+rEkCK1+VMLBFy+ttwxCJGtAIbQsGaP/bLHNI+fOr3f+yxTeZU+sVQX6who zs5ndcnJQFVY73EGPHMBFgykchFNEN++T8l38vrAOG3I7SrYfkSJ88gFXrpoA3XqOtvpZW vSXIBisCSR4z60ya2o5ZdQbx9DW5Lr7itLMy+UVrF69k1n0fD6sf9/3wGfb+NNZfeSMzJq ui2mH/LaiXKkOTB8FTTAQ0hgHUeRTiqe5KZUQIy+AJw+HCEwJ63Y/SfxpIEajA== To: netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, jreuter@yaina.de, linux-hams@vger.kernel.org, linux-kernel@vger.kernel.org, Mashiro Chen , stable@vger.kernel.org Subject: [PATCH net] net: ax25: fix integer overflow in ax25_rx_fragment() Date: Thu, 9 Apr 2026 01:25:21 +0800 Message-ID: <20260408172521.281365-1-mashiro.chen@mailbox.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-MBO-RS-META: ob97oaxaox1sbha7g397ai6mgwyxh754 X-MBO-RS-ID: 5f10e2ebca1b331472e The ax25_cb fragmentation reassembly accumulator: ax25->fraglen += skb->len; operates on the unsigned short field 'fraglen' declared in ax25_cb: unsigned short paclen, fragno, fraglen; When fragments accumulate with a combined payload exceeding 65535 bytes, fraglen wraps to near zero. The subsequent allocation: skb = alloc_skb(AX25_MAX_HEADER_LEN + ax25->fraglen, GFP_ATOMIC); then allocates a tiny buffer. Every skb_put() call in the copy loop that follows writes far beyond the allocated headroom, corrupting the kernel heap. An attacker on an AX.25 link that supports multi-fragment I-frames (AX25_SEG_FIRST / AX25_SEG_REM mechanism) can trigger this by sending enough continuation fragments to wrap the 16-bit counter. With AX.25 segment numbers limited to 6 bits (max 63 continuation fragments), a fragment payload of ~1040 bytes per fragment is sufficient to overflow. Fix mirrors the identical bug fixed in NET/ROM (nr_in.c): check for overflow before adding skb->len to fraglen, and abort fragment reassembly cleanly if the limit would be exceeded. Cc: stable@vger.kernel.org Cc: linux-hams@vger.kernel.org Signed-off-by: Mashiro Chen --- net/ax25/ax25_in.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ax25/ax25_in.c b/net/ax25/ax25_in.c index d75b3e9ed93de8..68202c19b19e3f 100644 --- a/net/ax25/ax25_in.c +++ b/net/ax25/ax25_in.c @@ -41,6 +41,11 @@ static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb) /* Enqueue fragment */ ax25->fragno = *skb->data & AX25_SEG_REM; skb_pull(skb, 1); /* skip fragno */ + if ((unsigned int)ax25->fraglen + skb->len > USHRT_MAX) { + skb_queue_purge(&ax25->frag_queue); + ax25->fragno = 0; + return 1; + } ax25->fraglen += skb->len; skb_queue_tail(&ax25->frag_queue, skb); -- 2.53.0