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From: Matheus Tavares <matheus.bernardino@usp.br>
To: git@vger.kernel.org
Cc: christian.couder@gmail.com, olyatelezhnaya@gmail.com,
	pclouds@gmail.com, gitster@pobox.com, jrnieder@gmail.com,
	Jonathan Tan <jonathantanmy@google.com>,
	Stefan Beller <stefanbeller@gmail.com>,
	Brandon Williams <bwilliams.eng@gmail.com>,
	"brian m. carlson" <sandals@crustytoothpaste.net>
Subject: [PATCH v2 03/11] grep: fix racy calls in grep_objects()
Date: Sun, 29 Sep 2019 22:50:49 -0300
Message-ID: <34aeb218bf266ac1a8fabcd9e8b307130d31eb0b.1569808052.git.matheus.bernardino@usp.br> (raw)
In-Reply-To: <cover.1569808052.git.matheus.bernardino@usp.br>

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 call with the
said grep_read_mutex.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
---
 builtin/grep.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/builtin/grep.c b/builtin/grep.c
index 626dbe554d..fa8b9996d1 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -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)) {
-- 
2.23.0


  parent reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-10 20:27 [GSoC][PATCH 0/4] grep: re-enable threads when cached, w/ parallel inflation Matheus Tavares
2019-08-10 20:27 ` [GSoC][PATCH 1/4] object-store: add lock to read_object_file_extended() Matheus Tavares
2019-08-10 20:27 ` [GSoC][PATCH 2/4] grep: allow locks to be enabled individually Matheus Tavares
2019-08-10 20:27 ` [GSoC][PATCH 3/4] grep: disable grep_read_mutex when possible Matheus Tavares
2019-08-10 20:27 ` [GSoC][PATCH 4/4] grep: re-enable threads in some non-worktree cases Matheus Tavares
2019-09-30  1:50 ` [PATCH v2 00/11] grep: improve threading and fix race conditions Matheus Tavares
2019-09-30  1:50   ` [PATCH v2 01/11] grep: fix race conditions on userdiff calls Matheus Tavares
2019-09-30  1:50   ` [PATCH v2 02/11] grep: fix race conditions at grep_submodule() Matheus Tavares
2019-09-30  1:50   ` Matheus Tavares [this message]
2019-09-30  1:50   ` [PATCH v2 04/11] replace-object: make replace operations thread-safe Matheus Tavares
2019-09-30  1:50   ` [PATCH v2 05/11] object-store: allow threaded access to object reading Matheus Tavares
2019-11-12  2:54     ` Jonathan Tan
2019-11-13  5:20       ` Jeff King
2019-11-14  5:57         ` Matheus Tavares Bernardino
2019-11-14  6:01           ` Jeff King
2019-11-14 18:15             ` Jonathan Tan
2019-11-15  4:12               ` Jeff King
2019-09-30  1:50   ` [PATCH v2 06/11] grep: replace grep_read_mutex by internal obj read lock Matheus Tavares
2019-10-01 19:23     ` [PATCH] squash! " Matheus Tavares
2019-09-30  1:50   ` [PATCH v2 07/11] submodule-config: add skip_if_read option to repo_read_gitmodules() Matheus Tavares
2019-09-30  1:50   ` [PATCH v2 08/11] grep: allow submodule functions to run in parallel Matheus Tavares
2019-09-30  1:50   ` [PATCH v2 09/11] grep: protect packed_git [re-]initialization Matheus Tavares
2019-09-30  1:50   ` [PATCH v2 10/11] grep: re-enable threads in non-worktree case Matheus Tavares
2019-09-30  1:50   ` [PATCH v2 11/11] grep: move driver pre-load out of critical section Matheus Tavares

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