Re: [PATCH v4 04/27] format-patch: don't leak "extra_headers" or "ref_message_ids"
- From
- Phillip Wood <phillip.wood123@gmail.com>
- Date
- Apr 1, 2022, 15:13 UTC
- Message-ID
- <851584aa-a31d-7446-4994-e641f298f0cd@gmail.com>
- In-Reply-To
- <patch-v4-04.27-69f0aabe38f-20220331T005325Z-avarab@gmail.com>
Hi Ævar
On 31/03/2022 02:11, Ævar Arnfjörð Bjarmason wrote:
Show 5 quoted lines
> Fix two memory leaks in "struct rev_info" by freeing that memory in > cmd_format_patch(). These two are unusual special-cases in being in > the "struct rev_info", but not being "owned" by the code in > revision.c. I.e. they're members of the struct so that this code in > "builtin/log.c" can pass information code in log-tree.c.
I'm not sure that I necessarily agree that these are owned by builtin/log.c. For rev.extra_headers it is set in builtin/log.c but never used there which makes me think we are transferring ownership to struct rev_info. For ref_message_ids it is less clear cut but having it owned by struct rev_info and freeing it in release_revisions() would make things clearer I think. Having some members owned by struct rev_info but others allocated and freed by other code is confusing and is likely to lead to memory errors. I don't think struct rev_info is borrowing a reference to these items as they are being allocated for it's exclusive use.
Best Wishes
Phillip
Show 48 quoted lines
> See 20ff06805c6 (format-patch: resurrect extra headers from config,
> 2006-06-02) and d1566f7883f (git-format-patch: Make the second and
> subsequent mails replies to the first, 2006-07-14) for the initial
> introduction of "extra_headers" and "ref_message_ids".
>
> We can count on repo_init_revisions() memset()-ing this data to 0
> however, so we can count on it being either NULL or something we
> allocated. In the case of "extra_headers" let's add a local "char *"
> variable to hold it, to avoid the eventual cast from "const char *"
> when we free() it.
>
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> ---
> builtin/log.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/builtin/log.c b/builtin/log.c
> index 634dc782cce..6f9928fabfe 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -1747,6 +1747,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
> struct commit *commit;
> struct commit **list = NULL;
> struct rev_info rev;
> + char *to_free = NULL;
> struct setup_revision_opt s_r_opt;
> int nr = 0, total, i;
> int use_stdout = 0;
> @@ -1947,7 +1948,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
> strbuf_addch(&buf, '\n');
> }
>
> - rev.extra_headers = strbuf_detach(&buf, NULL);
> + rev.extra_headers = to_free = strbuf_detach(&buf, NULL);
>
> if (from) {
> if (split_ident_line(&rev.from_ident, from, strlen(from)))
> @@ -2284,6 +2285,10 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
> strbuf_release(&rdiff1);
> strbuf_release(&rdiff2);
> strbuf_release(&rdiff_title);
> + free(to_free);
> + if (rev.ref_message_ids)
> + string_list_clear(rev.ref_message_ids, 0);
> + free(rev.ref_message_ids);
> UNLEAK(rev);
> return 0;
> }