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gvfs-helper: fix race condition when creating loose object dirs #205

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Merged
merged 1 commit into from
Oct 4, 2019
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gvfs-helper: fix race condition when creating loose object dirs #205

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4 changes: 3 additions & 1 deletion gvfs-helper.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1049,7 +1049,9 @@ static void create_tempfile_for_loose(
strbuf_complete(&buf_path, '/');
strbuf_add(&buf_path, hex, 2);

if (!file_exists(buf_path.buf) && mkdir(buf_path.buf, 0777) == -1) {
if (!file_exists(buf_path.buf) &&
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A bit unrelated, do you know if there is a function dir_exists that checks if the path exists as a directory (or should we add one to use here)?

I couldn't find one in dir.c, but I imagine all it would need is:

int dir_exists(const char *f)
{
	struct stat sb;
	if (lstat(f, &sb) != 0)
		return false;

	return S_ISDIR(sb.st_mode);
}

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The following exists in builtin/clone.c:

static int dir_exists(const char *path)
{
	struct stat sb;
	return !stat(path, &sb);
}

It doesn't check the S_ISDIR().

I do see your interest in checking the type to make sure there isn't a file in the way. I'm not sure if there is enough value.

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I'm not sure if there is enough value.

Yeah I was on the fence as well, we've not seen this be a problem thus far.

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Good catch. Thanks!
I'll fix it Monday. I think I can just try the mkdir() and catch the EEXIST error code.
I avoided that because of the platform nature of the error codes.
(or just try the lstat() again inside the error case.)

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Please note that there is not only a dir_exists(), but also an is_directory() function (the latter of which is public). There is even a ticket to reconcile them: gitgitgadget#230

mkdir(buf_path.buf, 0777) == -1 &&
!file_exists(buf_path.buf)) {
strbuf_addf(&status->error_message,
"cannot create directory for loose object '%s'",
buf_path.buf);
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