linux-kernel - Re: [PATCH][next] unicode: fix dereference of a potentially null pointer

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Date:   Sun, 28 Apr 2019 07:02:45 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Olaf Weber <olaf@....com>,
        Gabriel Krisman Bertazi <krisman@...labora.co.uk>,
        "Theodore Ts'o" <tytso@....edu>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Colin King <colin.king@...onical.com>,
        kernel-janitors@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][next] unicode: fix dereference of a potentially null pointer

Masahiro Yamada <yamada.masahiro@...ionext.com> writes:

> Forwarding because this file is not in my tree.
>
>
>
>
>
> On Sat, Apr 27, 2019 at 7:22 AM Colin King <colin.king@...onical.com> wrote:
>>
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> The pointer 'tree' is deferenced when assigning pointer 'trie', however
>> trie is being null checked a few lines later, so it could potentially
>> be null. Fix the potential null pointer dereference by only dereferencing
>> it after it has been null checked.
>>
>> Addresses-Coverity: ("Dereference before null check")
>> Fixes: b08fcacaaaf4 ("unicode: introduce UTF-8 character database")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>


Acked-by: Gabriel Krisman Bertazi <krisman@...labora.com>

Ted, can you pick this up directly for now?

>> ---
>>  scripts/mkutf8data.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/scripts/mkutf8data.c b/scripts/mkutf8data.c
>> index 12ce94b43be6..0563ba679bbb 100644
>> --- a/scripts/mkutf8data.c
>> +++ b/scripts/mkutf8data.c
>> @@ -2706,7 +2706,7 @@ static utf8leaf_t *utf8hangul(const char *str, unsigned char *hangul)
>>  static utf8leaf_t *utf8nlookup(struct tree *tree, unsigned char *hangul,
>>                                const char *s, size_t len)
>>  {
>> -       utf8trie_t      *trie = utf8data + tree->index;
>> +       utf8trie_t      *trie;
>>         int             offlen;
>>         int             offset;
>>         int             mask;
>> @@ -2716,6 +2716,7 @@ static utf8leaf_t *utf8nlookup(struct tree *tree, unsigned char *hangul,
>>                 return NULL;
>>         if (len == 0)
>>                 return NULL;
>> +       trie = utf8data + tree->index;
>>         node = 1;
>>         while (node) {
>>                 offlen = (*trie & OFFLEN) >> OFFLEN_SHIFT;
>> --
>> 2.20.1
>>
>
>
> --
> Best Regards
> Masahiro Yamada

-- 
Gabriel Krisman Bertazi