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 EAEF1216E30; Tue, 29 Apr 2025 16:46:04 +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=1745945165; cv=none; b=VwHyY2AUVSsDFnP3cqZYe9UhgtvpKCVcbNn5HFzuFMNhnkFcJ0/c2Z/sXIQFel6wNlkIIjDCNpQycFbl9Jtdt7SlQcOSfb0E+8Jpn7GsI608JuRuzFiEURQN/QRzbiaJ7HoIl5T6ZCvSLPCZ+5H3UXgEu/7ydyU5kR7rtKnWdDw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745945165; c=relaxed/simple; bh=NNdtKwxceGzp/5bLg2SpopcxrzJHCGm7lnZCtx0pczE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=cIy8p1AjAALFX2oK8w6r2nsDGTR49TdOG+owAoHPNmvmcbGzYDv1xqhtF+9qVkaIBr3S3q3v/nXlMr9BDeE8HiwkVpnA0wcmgeyneOv0cicQXyB4AXyJsbWRLRVcgu8mFhsvdzzoQ6us5xt76Hlm4+40ezoy0Rtbr6zJRqrz6fM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0eNKbA/W; 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="0eNKbA/W" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0A61CC4CEE3; Tue, 29 Apr 2025 16:46:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1745945164; bh=NNdtKwxceGzp/5bLg2SpopcxrzJHCGm7lnZCtx0pczE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0eNKbA/W11CmDPe7Qq4ufNE03NZUG01+QIUqG8GZLeuPnM5KVIbn08HbPwsB8FnhL uBSyd3aqsWy4F7soiTkYE/VH+3Y6JswilOjp/b/cg+rXSt1a3RLp0Zk0RkhS/MGPUj VsnTBC3TniWEF0bP0MCckA3oosCv4Cuozy1U8vZs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+29fc8991b0ecb186cf40@syzkaller.appspotmail.com, Arnaud Lecomte , Paolo Abeni , Sasha Levin Subject: [PATCH 5.4 006/179] net: ppp: Add bound checking for skb data on ppp_sync_txmung Date: Tue, 29 Apr 2025 18:39:07 +0200 Message-ID: <20250429161049.650375963@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250429161049.383278312@linuxfoundation.org> References: <20250429161049.383278312@linuxfoundation.org> User-Agent: quilt/0.68 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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Arnaud Lecomte [ Upstream commit aabc6596ffb377c4c9c8f335124b92ea282c9821 ] Ensure we have enough data in linear buffer from skb before accessing initial bytes. This prevents potential out-of-bounds accesses when processing short packets. When ppp_sync_txmung receives an incoming package with an empty payload: (remote) gef➤ p *(struct pppoe_hdr *) (skb->head + skb->network_header) $18 = { type = 0x1, ver = 0x1, code = 0x0, sid = 0x2, length = 0x0, tag = 0xffff8880371cdb96 } from the skb struct (trimmed) tail = 0x16, end = 0x140, head = 0xffff88803346f400 "4", data = 0xffff88803346f416 ":\377", truesize = 0x380, len = 0x0, data_len = 0x0, mac_len = 0xe, hdr_len = 0x0, it is not safe to access data[2]. Reported-by: syzbot+29fc8991b0ecb186cf40@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=29fc8991b0ecb186cf40 Tested-by: syzbot+29fc8991b0ecb186cf40@syzkaller.appspotmail.com Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Arnaud Lecomte Link: https://patch.msgid.link/20250408-bound-checking-ppp_txmung-v2-1-94bb6e1b92d0@arnaud-lcm.com [pabeni@redhat.com: fixed subj typo] Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- drivers/net/ppp/ppp_synctty.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/net/ppp/ppp_synctty.c b/drivers/net/ppp/ppp_synctty.c index 55641e01192dd..9ebd1ac569b90 100644 --- a/drivers/net/ppp/ppp_synctty.c +++ b/drivers/net/ppp/ppp_synctty.c @@ -516,6 +516,11 @@ ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb) unsigned char *data; int islcp; + /* Ensure we can safely access protocol field and LCP code */ + if (!pskb_may_pull(skb, 3)) { + kfree_skb(skb); + return NULL; + } data = skb->data; proto = get_unaligned_be16(data); -- 2.39.5