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 D38EF28686; Thu, 9 Apr 2026 02:50:47 +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=1775703049; cv=none; b=WwNQgbkTI2OqKODtcSXOf8HBUZsz+IQP2zSMfN92Bv+SbTDjjy8udrNc7sr870+3pwPxTOWYlEO/sjxVoltMphZS1WQaHRIi7w3f9HQmjKKjig64P9bQxrRpEjCVi7ckf/eu0nVWuRZ/DpHuyVRoDIMt4CVznvsv14LuhhRtNTw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775703049; c=relaxed/simple; bh=5J5ZO6fBKGSx8kRLsewuIHgetXG4DNnuNKeDnEdeSL8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=J6cQP3XWUQwNRVLusYwfmGIlf/BcYvv5h4qkf+dqVzCH72qBSFCsC4iNhvjTqACZLl5MuhcsUfMrQWP0jkNbcNNVwx4IY6b3cVEQvQdYfEvmEFBhc7wp7QrZA0+kNF3DcDEg1O8kk8wwDgxZALarAuXNzCI4nxjd01JMK5u1oCU= 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=G60PAVWB; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b=YaK8ZsWs; 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="G60PAVWB"; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b="YaK8ZsWs" Received: from smtp2.mailbox.org (smtp2.mailbox.org [IPv6:2001:67c:2050:b231:465::2]) (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 4frkvV17YzzB12V; Thu, 9 Apr 2026 04:50:46 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1775703046; 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=pffMbmSi5wWfzvmmZ19zBe3ASxdB2Pb24bLa/ZO63cc=; b=G60PAVWB3rClMPUhUvDATFIeEh/6a7M2W3xxyTpXiSQRNtSedWXDdMALE93vjyzhgeFPqa 1ka/WBaO3K+Pra0mo62yblLLQyBRLHuFAG4hY85L1BovUvRh8RcxTRXta9XPRhmo7fJcEk QHen7Hxb8WCfuqkPP7lJF2Ix+VsNkhmWzBihZccXHOa+JkQ3w0QRNLJ+wmEgvO82ej7N0x X5wEndRXaMdNTIFauPbSeaUOVJWVfhjjGhUtDgT4aeq7O7ithWMemV73Weagsq+NuLyDsZ UGavlouYcnhVFrTJrqaxLzN7u3N1uds/lAfoY/dShTeaRI+DtnCF3kBJB0IOLg== Authentication-Results: outgoing_mbo_mout; dkim=pass header.d=mailbox.org header.s=mail20150812 header.b=YaK8ZsWs; spf=pass (outgoing_mbo_mout: domain of mashiro.chen@mailbox.org designates 2001:67c:2050:b231:465::2 as permitted sender) smtp.mailfrom=mashiro.chen@mailbox.org From: Mashiro Chen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1775703044; 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=pffMbmSi5wWfzvmmZ19zBe3ASxdB2Pb24bLa/ZO63cc=; b=YaK8ZsWs+GlKI8nrLchTNB+pHwLAAgMMHDUP9oaM7X3I2WWwFT17fW3m7d9tp+Nl6YZbHh mU0lETsHpZtbMTNfVoo7NI7QxdxO2tGRGfu5cJSqGzXZMatKEDvJHrA5ktpv0kcAddNR6G w33mj9etJJEhaSYwxFW5Z4kdSE8Acrcs46P3mcm2YByVD2zoxB9URCtzmN1OjZainoeiOZ 56ga7f0bCpQeiRsLSiqV7P4e1VDZXkt9uVmg75C2iaGK0VFenftYF5knKbviY7JD400ZI1 MBRHUDnoiNzGqM0vFpgeguqO1NIw3vQ06ZIPPwPdYCzULeJQjhKnWonmEbdI4A== 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 v2 net] net: ax25: fix integer overflow in ax25_rx_fragment() Date: Thu, 9 Apr 2026 10:50:26 +0800 Message-ID: <20260409025026.24575-1-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: 35ib8kudtt1jz7rqdyz1rkbsa6k8ye6u X-MBO-RS-ID: 5f4dc865e5cefd5ceb9 X-Rspamd-Queue-Id: 4frkvV17YzzB12V 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 7 bits (max 127 continuation fragments), a fragment payload of ~516 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 Acked-by: Joerg Reuter 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