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 1F454227E95; Tue, 29 Apr 2025 17:41:46 +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=1745948506; cv=none; b=GdlLbRGASqg4BnumYjBf7bcoSftqOys7E+2tVmEI/GmHeMbIA4Aa0u/5CqmnLRiMABJT7nnwMG2ruJOYmzTtbCFBKfVsi98z92CwChmpYK4Y/DCQJmaNS5SusjyWp6r5FFmLyr12gg8vkUusRm91eaNWgeM7esvHpGdDNK+kQMw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745948506; c=relaxed/simple; bh=POIR63RR4E86wO7h30Q8vShM/jz451XqOS9jk5HpaAM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=cujH9rI7MGdEXCBDBi7e7w1GbzPLebTZFewqEk7wXhmpSw+geVH7ICfkXvBzI/vd6ounjqluLjotP+3XjUKH8U2GHu3zVgOozKAz5OIZQszR11FUy8HWrGWy3Q0hRavmqNWIK3B+oxORZ0hypPCMcaQBSkWRtAGBTzpyc4afb40= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TXVZtM+y; 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="TXVZtM+y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A7CAEC4CEE3; Tue, 29 Apr 2025 17:41:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1745948506; bh=POIR63RR4E86wO7h30Q8vShM/jz451XqOS9jk5HpaAM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TXVZtM+yyWpPyw0iX3vx0G0aNnpKbgXY3p53/L1CjiM81uzeEBe8jWc62EoqReqqR u1yCCf/OD+ioiFs7a1nWnWPYsfzJWYpugWCdBsJDi6cD0c0czh9bJY3e+uF+7vKhWJ cu5H0mtPfFD7oBl5dSSH8oD1KcHpWuhflu2IenkU= 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 5.15 009/373] net: ppp: Add bound checking for skb data on ppp_sync_txmung Date: Tue, 29 Apr 2025 18:38:06 +0200 Message-ID: <20250429161123.517904993@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250429161123.119104857@linuxfoundation.org> References: <20250429161123.119104857@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 5.15-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 692c558beed54..c8d9c580ed503 100644 --- a/drivers/net/ppp/ppp_synctty.c +++ b/drivers/net/ppp/ppp_synctty.c @@ -517,6 +517,11 @@ 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