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 2D196175BF; Wed, 23 Apr 2025 14:54:52 +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=1745420092; cv=none; b=tdPHsaM19KxCLTGmO00pJLFovkBlComeEE8hOs1PoZTVs1v4wHesjGip4sYQ/MWXOYQpKlvaHSOcKH+IwP8qfyoCoZrN/kQOPoRltduD4bmdYR5ExDpRps6d+/7fi6tsM8f/zcTa4oKkJBRW+9H3bENoehL9+Gm7/p+rG1CPSZU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745420092; c=relaxed/simple; bh=m6IQi1jidH0qivW3cJGPapwrYm1BZ4Zo2gnF1W00iiI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=mwIKK0SGhAoyF30L3fz2HFZYg1IkmtzcKGORbMeJ0voziGw2ssaKW1M2bR6E1N9AicpF9ykz/a5pefsmlqU+/zM5W2aTM7tNETdlSF/lwyaQW2h84aeXw/dfI8uhxP3bPNzQZZCSMIItizjQJdeMZ/1Uv3AyL5UW6eUAfX/4sOA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=RtCF6RZz; 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="RtCF6RZz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B504DC4CEE2; Wed, 23 Apr 2025 14:54:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1745420092; bh=m6IQi1jidH0qivW3cJGPapwrYm1BZ4Zo2gnF1W00iiI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RtCF6RZzLDyqKhr+gHY1zuTDbyymIazxDjE1yqQI0vTvTIBWXRy2cn0yCXx+1qa04 gsg6WSdENpgOUn7tuUykM/tHmp2OOADGFkFsym7evfJF3Ka3F6tEbW9oyv3BzEqm4I 6voD8oaTLf/5QoIqDurQ+KX/N6EhT0XRxbtVDY6I= 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 6.1 016/291] net: ppp: Add bound checking for skb data on ppp_sync_txmung Date: Wed, 23 Apr 2025 16:40:05 +0200 Message-ID: <20250423142625.069033314@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250423142624.409452181@linuxfoundation.org> References: <20250423142624.409452181@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 6.1-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 94ef6f9ca5103..fb533c43deeea 100644 --- a/drivers/net/ppp/ppp_synctty.c +++ b/drivers/net/ppp/ppp_synctty.c @@ -515,6 +515,11 @@ 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