From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Phil Sutter <phil@nwl.cc>
Cc: netfilter-devel@vger.kernel.org
Subject: Re: [nft PATCH 1/4] evaluate: Fix datalen checks in expr_evaluate_string()
Date: Wed, 17 Aug 2016 16:41:25 +0200 [thread overview]
Message-ID: <20160817144125.GA10362@salvia> (raw)
In-Reply-To: <1471017610-3473-2-git-send-email-phil@nwl.cc>
On Fri, Aug 12, 2016 at 06:00:07PM +0200, Phil Sutter wrote:
> This part of the code is pretty weird due to suboptimal variable name
> choice: 'data', 'len', 'datalen', 'data_len'.
>
> But even without understanding all of it, the code checking 'datalen - 1
> >= 0' assumes 'datalen - 1' may actually become negative, which is not
> true since it is unsigned. So make 'datalen' a signed integer instead.
>
> Another issue is the check for "data[datalen] != '*'" which will access
> unallocated memory if 'strlen(data) == 0'. So make sure 'datalen >= 0'
> before using it as array index.
We don't allow empty strings from our flex scanner as string, so we
assume the string is at least 1.
You can probably add an assert() here instead.
next prev parent reply other threads:[~2016-08-17 14:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-12 16:00 [nft PATCH 0/4] A round of covscan indicated fixes Phil Sutter
2016-08-12 16:00 ` [nft PATCH 1/4] evaluate: Fix datalen checks in expr_evaluate_string() Phil Sutter
2016-08-17 14:41 ` Pablo Neira Ayuso [this message]
2016-08-12 16:00 ` [nft PATCH 2/4] netlink_delinearize: Avoid potential null pointer deref Phil Sutter
2016-08-17 14:46 ` Pablo Neira Ayuso
2016-08-12 16:00 ` [nft PATCH 3/4] proto_find_num: Avoid potential null pointer dereference Phil Sutter
2016-08-17 14:47 ` Pablo Neira Ayuso
2016-08-12 16:00 ` [nft PATCH 4/4] evaluate: Avoid undefined behaviour in concat_subtype_id() Phil Sutter
2016-08-17 14:51 ` Pablo Neira Ayuso
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