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grep: fix racy calls in grep_objects() 

deref_tag() calls is_promisor_object() and parse_object(), both of which
perform lazy initializations and other thread-unsafe operations. If it
was only called by grep_objects() this wouldn't be a problem as the
latter is only executed by the main thread. However, deref_tag() is also
present in read_object_file()'s call stack. So calling deref_tag() in
grep_objects() without acquiring the grep_read_mutex may incur in a race
condition with object reading operations (such as the ones internally
performed by fill_textconv(), called at fill_textconv_grep()). The same
problem happens with the call to gitmodules_config_oid() which also has
parse_object() in its call stack. Fix that protecting both calls with
the said grep_read_mutex.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Matheus Tavares 2020-01-15 23:39:51 -03:00 committed by Junio C Hamano
parent faf123c730
commit d5b0bac528
1 changed files with 5 additions and 0 deletions
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5
builtin/grep.c
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@ -658,13 +658,18 @@ static int grep_objects(struct grep_opt *opt, const struct pathspec *pathspec,
for (i = 0; i < nr; i++) {
struct object *real_obj;
grep_read_lock();
real_obj = deref_tag(opt->repo, list->objects[i].item,
NULL, 0);
grep_read_unlock();
/* load the gitmodules file for this rev */
if (recurse_submodules) {
submodule_free(opt->repo);
grep_read_lock();
gitmodules_config_oid(&real_obj->oid);
grep_read_unlock();
}
if (grep_object(opt, pathspec, real_obj, list->objects[i].name,
list->objects[i].path)) {