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From: Junio C Hamano <gitster@pobox.com>
To: git@vger.kernel.org
Cc: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: [PATCH v2 3/4] commit-graph.c: don't assume that stat() succeeds
Date: Thu, 12 May 2022 15:32:17 -0700	[thread overview]
Message-ID: <20220512223218.237544-4-gitster@pobox.com> (raw)
In-Reply-To: <20220512223218.237544-1-gitster@pobox.com>

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>

Fix code added in 8d84097f965 (commit-graph: expire commit-graph
files, 2019-06-18) to check the return value of the stat() system
call. Not doing so caused us to use uninitialized memory in the "Bloom
generation is limited by --max-new-filters" test in
t4216-log-bloom.sh:

	+ rm -f trace.event
	+ pwd
	+ GIT_TRACE2_EVENT=[...]/t/trash directory.t4216-log-bloom/limits/trace.event git commit-graph write --reachable --split=replace --changed-paths --max-new-filters=2
	==24835== Syscall param utimensat(times[0].tv_sec) points to uninitialised byte(s)
	==24835==    at 0x499E65A: __utimensat64_helper (utimensat.c:34)
	==24835==    by 0x4999142: utime (utime.c:36)
	==24835==    by 0x552BE0: mark_commit_graphs (commit-graph.c:2213)
	==24835==    by 0x550822: write_commit_graph (commit-graph.c:2424)
	==24835==    by 0x54E3A0: write_commit_graph_reachable (commit-graph.c:1681)
	==24835==    by 0x4374BB: graph_write (commit-graph.c:269)
	==24835==    by 0x436F7D: cmd_commit_graph (commit-graph.c:326)
	==24835==    by 0x407B9A: run_builtin (git.c:465)
	==24835==    by 0x406651: handle_builtin (git.c:719)
	==24835==    by 0x407575: run_argv (git.c:786)
	==24835==    by 0x406410: cmd_main (git.c:917)
	==24835==    by 0x511F09: main (common-main.c:56)
	==24835==  Address 0x1ffeffde70 is on thread 1's stack
	==24835==  in frame #1, created by utime (utime.c:25)
	==24835==  Uninitialised value was created by a stack allocation
	==24835==    at 0x552B50: mark_commit_graphs (commit-graph.c:2201)
	==24835==
	[...]
	error: last command exited with $?=126
	not ok 137 - Bloom generation is limited by --max-new-filters

This would happen as we stat'd the non-existing
".git/objects/info/commit-graph" file. Let's fix mark_commit_graphs()
to check the stat()'s return value, and while we're at it fix another
case added in the same commit to do the same.

The caller in expire_commit_graphs() would have been less likely to
run into this, as it's operating on files it just got from readdir(),
but it could still happen due to a race with e.g. a concurrent "rm
-rf" of the commit-graph files.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 commit-graph.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index 441b36016b..2b52818731 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -2206,7 +2206,8 @@ static void mark_commit_graphs(struct write_commit_graph_context *ctx)
 		struct stat st;
 		struct utimbuf updated_time;
 
-		stat(ctx->commit_graph_filenames_before[i], &st);
+		if (stat(ctx->commit_graph_filenames_before[i], &st) < 0)
+			continue;
 
 		updated_time.actime = st.st_atime;
 		updated_time.modtime = now;
@@ -2247,7 +2248,8 @@ static void expire_commit_graphs(struct write_commit_graph_context *ctx)
 		strbuf_setlen(&path, dirnamelen);
 		strbuf_addstr(&path, de->d_name);
 
-		stat(path.buf, &st);
+		if (stat(path.buf, &st) < 0)
+			continue;
 
 		if (st.st_mtime > expire_time)
 			continue;
-- 
2.36.1-338-g1c7f76a54c


  parent reply	other threads:[~2022-05-12 22:36 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-21 20:14 [PATCH 0/4] Fix issues and a regression noted by valgrind Ævar Arnfjörð Bjarmason
2022-04-21 20:14 ` [PATCH 1/4] tests: make RUNTIME_PREFIX compatible with --valgrind Ævar Arnfjörð Bjarmason
2022-04-21 22:22   ` Junio C Hamano
2022-04-21 20:14 ` [PATCH 2/4] log test: skip a failing mkstemp() test under valgrind Ævar Arnfjörð Bjarmason
2022-04-21 20:14 ` [PATCH 3/4] commit-graph.c: don't assume that stat() succeeds Ævar Arnfjörð Bjarmason
2022-04-21 22:29   ` Junio C Hamano
2022-04-21 20:14 ` [PATCH 4/4] object-file: fix a unpack_loose_header() regression in 3b6a8db3b03 Ævar Arnfjörð Bjarmason
2022-04-21 22:39   ` Junio C Hamano
2022-04-22  8:21     ` Ævar Arnfjörð Bjarmason
2022-05-12 22:32 ` [PATCH v2 0/4] test fixes around valgrind Junio C Hamano
2022-05-12 22:32   ` [PATCH v2 1/4] tests: using custom GIT_EXEC_PATH breaks --valgrind tests Junio C Hamano
2022-05-12 22:32   ` [PATCH v2 2/4] log test: skip a failing mkstemp() test under valgrind Junio C Hamano
2022-05-12 22:32   ` Junio C Hamano [this message]
2022-05-12 22:32   ` [PATCH v2 4/4] object-file: fix a unpack_loose_header() regression in 3b6a8db3b03 Junio C Hamano
2022-05-12 23:39     ` Junio C Hamano
2022-05-16 14:59       ` Derrick Stolee
2022-05-19 20:09         ` [RFC PATCH 0/2] Alternate ab/valgrind-fixes fix-up Ævar Arnfjörð Bjarmason
2022-05-19 20:09           ` [RFC PATCH 1/2] object-file API: fix obscure unpack_loose_header() return Ævar Arnfjörð Bjarmason
2022-05-19 20:09           ` [RFC PATCH 2/2] object-file API: have unpack_loose_header() return "int" again Ævar Arnfjörð Bjarmason
2022-05-20  4:27             ` Junio C Hamano

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