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win: fix thread race in uv_cwd() and uv_chdir() (#3708)

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Another thread can change the working directory between calls to
GetCurrentDirectoryW().

The first call was used to determine the size of the buffer to use in
the second call. Retry if the reported size does not match the expected
size because the buffer's contents is undefined in that case.
This commit is contained in:
Ben Noordhuis 2022-07-28 00:34:03 +02:00 committed by GitHub
parent 850f002cb2
commit 4db0a9a6b7
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 57 additions and 43 deletions
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100
src/win/util.c
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@ -148,6 +148,51 @@ int uv_exepath(char* buffer, size_t* size_ptr) {
}
static int uv__cwd(WCHAR** buf, DWORD *len) {
WCHAR* p;
DWORD n;
DWORD t;
t = GetCurrentDirectoryW(0, NULL);
for (;;) {
if (t == 0)
return uv_translate_sys_error(GetLastError());
/* |t| is the size of the buffer _including_ nul. */
p = uv__malloc(t * sizeof(*p));
if (p == NULL)
return UV_ENOMEM;
/* |n| is the size of the buffer _excluding_ nul but _only on success_.
* If |t| was too small because another thread changed the working
* directory, |n| is the size the buffer should be _including_ nul.
* It therefore follows we must resize when n >= t and fail when n == 0.
*/
n = GetCurrentDirectoryW(t, p);
if (n > 0)
if (n < t)
break;
uv__free(p);
t = n;
}
/* The returned directory should not have a trailing slash, unless it points
* at a drive root, like c:\. Remove it if needed.
*/
t = n - 1;
if (p[t] == L'\\' && !(n == 3 && p[1] == L':')) {
p[t] = L'\0';
n = t;
}
*buf = p;
*len = n;
return 0;
}
int uv_cwd(char* buffer, size_t* size) {
DWORD utf16_len;
WCHAR *utf16_buffer;
@ -157,27 +202,9 @@ int uv_cwd(char* buffer, size_t* size) {
return UV_EINVAL;
}
utf16_len = GetCurrentDirectoryW(0, NULL);
if (utf16_len == 0) {
return uv_translate_sys_error(GetLastError());
}
utf16_buffer = uv__malloc(utf16_len * sizeof(WCHAR));
if (utf16_buffer == NULL) {
return UV_ENOMEM;
}
utf16_len = GetCurrentDirectoryW(utf16_len, utf16_buffer);
if (utf16_len == 0) {
uv__free(utf16_buffer);
return uv_translate_sys_error(GetLastError());
}
/* The returned directory should not have a trailing slash, unless it points
* at a drive root, like c:\. Remove it if needed. */
if (utf16_buffer[utf16_len - 1] == L'\\' &&
!(utf16_len == 3 && utf16_buffer[1] == L':')) {
utf16_len--;
utf16_buffer[utf16_len] = L'\0';
r = uv__cwd(&utf16_buffer, &utf16_len);
if (r < 0) {
return r;
}
/* Check how much space we need */
@ -220,8 +247,9 @@ int uv_cwd(char* buffer, size_t* size) {
int uv_chdir(const char* dir) {
WCHAR *utf16_buffer;
size_t utf16_len, new_utf16_len;
size_t utf16_len;
WCHAR drive_letter, env_var[4];
int r;
if (dir == NULL) {
return UV_EINVAL;
@ -259,29 +287,15 @@ int uv_chdir(const char* dir) {
/* Windows stores the drive-local path in an "hidden" environment variable,
* which has the form "=C:=C:\Windows". SetCurrentDirectory does not update
* this, so we'll have to do it. */
new_utf16_len = GetCurrentDirectoryW(utf16_len, utf16_buffer);
if (new_utf16_len > utf16_len ) {
uv__free(utf16_buffer);
utf16_buffer = uv__malloc(new_utf16_len * sizeof(WCHAR));
if (utf16_buffer == NULL) {
/* When updating the environment variable fails, return UV_OK anyway.
* We did successfully change current working directory, only updating
* hidden env variable failed. */
return 0;
}
new_utf16_len = GetCurrentDirectoryW(new_utf16_len, utf16_buffer);
}
if (utf16_len == 0) {
uv__free(utf16_buffer);
r = uv__cwd(&utf16_buffer, &utf16_len);
if (r == UV_ENOMEM) {
/* When updating the environment variable fails, return UV_OK anyway.
* We did successfully change current working directory, only updating
* hidden env variable failed. */
return 0;
}
/* The returned directory should not have a trailing slash, unless it points
* at a drive root, like c:\. Remove it if needed. */
if (utf16_buffer[utf16_len - 1] == L'\\' &&
!(utf16_len == 3 && utf16_buffer[1] == L':')) {
utf16_len--;
utf16_buffer[utf16_len] = L'\0';
if (r < 0) {
return r;
}
if (utf16_len < 2 || utf16_buffer[1] != L':') {