From: John Cai <johncai86@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: John Cai via GitGitGadget <gitgitgadget@gmail.com>, git@vger.kernel.org
Subject: Re: [PATCH v3] receive-pack.c: consolidate find header logic
Date: Tue, 4 Jan 2022 10:12:11 -0500 [thread overview]
Message-ID: <CAE7F284-4D3F-4412-ACC1-216BB93F74EB@gmail.com> (raw)
In-Reply-To: <xmqq35m4gt5x.fsf@gitster.g>
> On Jan 3, 2022, at 8:56 PM, Junio C Hamano <gitster@pobox.com> wrote:
>
> "John Cai via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
>> + size_t out_len;
>> + const char *val = find_header_mem(msg, len, key, &out_len);
>> +
>> + if (val == NULL)
>
> Style:
>
> if (!val)
>
>> + return NULL;
>> +
>> + if (next_line)
>> + *next_line = val + out_len + 1;
>> +
>> + return xmemdupz(val, out_len);
>> }
>>
>> /*
>> diff --git a/commit.c b/commit.c
>> index a348f085b2b..8ac32a4d7b5 100644
>> --- a/commit.c
>> +++ b/commit.c
>> @@ -1631,12 +1631,13 @@ struct commit_list **commit_list_append(struct commit *commit,
>> return &new_commit->next;
>> }
>>
>> -const char *find_commit_header(const char *msg, const char *key, size_t *out_len)
>> +const char *find_header_mem(const char *msg, size_t len,
>> + const char *key, size_t *out_len)
>> {
>> int key_len = strlen(key);
>> const char *line = msg;
>>
>> + while (line && line < msg + len) {
>> const char *eol = strchrnul(line, '\n');
>
> Between line[0] and msg[len], there may not be a LF nor NUL at all,
> and strchrnul() will scan beyond the range we were given (which is
> msg[0]..msg[len]).
>
> But that is something we share with the find_header() if I am not
> mistaken, so I am OK to leave the code as posted and leave it
> outside the scope of this series to clean it up to make it safer.
Good catch. Thanks for pointing that out-I didn’t notice it. I’ve added a NEEDSWORK
Block to this so we can address it in a later patch series.
>
> The reason why it is probably safe for the current set of callers
> (and presumably any reasonable new callers we may add later) is that
> they computed "len" by scanning the block of memory starting at (or
> before) "msg" before calling us, and we know that the block of
> memory is properly NUL-terminated. find_header() is called by
> check_nonce() and check_cert_push_options(), both of which tell
> us to scan in a strbuf, which is designed to be scannable for NUL
> safely by having an extra NUL at the end beyond the end.
>
next prev parent reply other threads:[~2022-01-04 15:12 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-27 18:26 [PATCH 0/2] Consolidate find_header logic into one function John Cai via GitGitGadget
2021-12-27 18:26 ` [PATCH 1/2] receive-pack.c: consolidate find header logic John Cai via GitGitGadget
2021-12-27 22:33 ` Junio C Hamano
2021-12-27 18:26 ` [PATCH 2/2] commit.c: rename find_commit_header to find_header John Cai via GitGitGadget
2021-12-29 6:19 ` [PATCH v2] receive-pack.c: consolidate find header logic John Cai via GitGitGadget
2021-12-30 23:01 ` Junio C Hamano
2021-12-31 6:17 ` [PATCH v3] " John Cai via GitGitGadget
2022-01-04 1:56 ` Junio C Hamano
2022-01-04 15:12 ` John Cai [this message]
2022-01-05 15:21 ` [PATCH v4] " John Cai via GitGitGadget
2022-01-05 20:10 ` Junio C Hamano
2022-01-06 0:51 ` [PATCH v5] " John Cai via GitGitGadget
2022-01-06 19:40 ` Junio C Hamano
2022-01-06 20:07 ` [PATCH v6] " John Cai via GitGitGadget
2022-01-08 4:54 ` John Cai
2022-01-08 7:11 ` Junio C Hamano
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