From: Phillip Wood Date: Fri, 01 Apr 2022 15:13:48 GMT Subject: Re: [PATCH v4 04/27] format-patch: don't leak "extra_headers" or "ref_message_ids" Message-ID: <851584aa-a31d-7446-4994-e641f298f0cd@gmail.com> In-Reply-To: Hi Ævar On 31/03/2022 02:11, Ævar Arnfjörð Bjarmason wrote: > 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 > 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 > --- > 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; > }