Karsten Blees <karsten.blees@xxxxxxxxx> writes:
> The coredumps are caused by my patch #10, which free()s
> cache_entries when they are removed, in combination with ...
Looking at that patch, it makes me wonder if remove_index_entry_at()
and replace_index_entry() should be the ones that frees the old
entry in the first place. A caller may already have a ce pointing
at an old entry and use the information from old_ce to update a new
one after it installed it, e.g.
old_ce = ...
new_ce = make_cache_entry(... old_ce->name, ...);
replace_index_entry(... new_ce);
new_ce->ce_mode = old_ce->cd_mode;
free(old_ce);
The same goes for the functions that remove the entry.
But I am probably biased saying this, because in the old days, cache
entries could never be freed (they were carved out of a contiguous
region of memory, mmapped from the index file). These days, we
parse and run ntoh*() on the on-disk cache entries to create in-core
form, and the "cache entries should never be freed" is no longer
true, but I would not be surprised if there are still some code
leftover that relies on "use after free" being safe, leaking unused
cache entries.
Going forward, I do agree with your patch #10 that removal or
replacing that may make an existing entry unreferenced should free
entries that are no longer used, and "use after free" should be
forbidden.
> Can't we just use add_file_to_cache here (which replaces
> cache_entries by creating a copy)?
>
> diff --git a/submodule.c b/submodule.c
> index 1905d75..e388487 100644
> --- a/submodule.c
> +++ b/submodule.c
> @@ -116,30 +116,7 @@ int remove_path_from_gitmodules(const char *path)
>
> void stage_updated_gitmodules(void)
> {
> - struct strbuf buf = STRBUF_INIT;
> - struct stat st;
> - int pos;
> - struct cache_entry *ce;
> - int namelen = strlen(".gitmodules");
> -
> - pos = cache_name_pos(".gitmodules", namelen);
> - if (pos < 0) {
> - warning(_("could not find .gitmodules in index"));
> - return;
> - }
I think the remainder is (morally) equivalent between the original
and a single "add-file-to-cache" call, and the version after your
"how about this" patch in the message I am responding to looks more
correct (e.g. why does the original lstat after it has read the
file?).
But this warning may want to stay, no?
> - ce = active_cache[pos];
> - ce->ce_flags = namelen;
> - if (strbuf_read_file(&buf, ".gitmodules", 0) < 0)
> - die(_("reading updated .gitmodules failed"));
> - if (lstat(".gitmodules", &st) < 0)
> - die_errno(_("unable to stat updated .gitmodules"));
> - fill_stat_cache_info(ce, &st);
> - ce->ce_mode = ce_mode_from_stat(ce, st.st_mode);
> - if (remove_cache_entry_at(pos) < 0)
> - die(_("unable to remove .gitmodules from index"));
> - if (write_sha1_file(buf.buf, buf.len, blob_type, ce->sha1))
> - die(_("adding updated .gitmodules failed"));
> - if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE))
> + if (add_file_to_cache(".gitmodules", 0))
> die(_("staging updated .gitmodules failed"));
> }
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