commit-graph.c: don't assume that stat() succeeds

Fix code added in 8d84097f96 (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>
This commit is contained in:
Ævar Arnfjörð Bjarmason 2022-05-12 15:32:17 -07:00 коммит произвёл Junio C Hamano
Родитель 4627c67fa6
Коммит 7c898554d7
1 изменённых файлов: 4 добавлений и 2 удалений

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@ -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;