[PATCH v2 1/1] Path string from the host should not be treated as wchar_t

yasuenag
2025-06-02T23:56:22Z

hv_fcopy_uio_daemon handles file copy request from the host.
(e.g. Copy-VMFile commandlet)
The request has file path and its name, they would be stored as
__u16 arrays in struct hv_start_fcopy. They are casted to wchar_t*
in fcopyd to convert to UTF-8 string. wchar_t is 32bit in Linux
unlike Windows (16bit), so string conversion would be failed and
the user cannot copy file to Linux guest from Host via fcopyd.

fcopyd converts each characters to char if the value is less
than 0x80. Thus we can convert straightly without wcstombs() call,
it means we are no longer to convert to wchar_t.

Length of path depends on PATH_MAX (Linux) and W_MAX_PATH (Windows),
so this change also addes new check to snprintf() call to make
target path.

Signed-off-by: Yasumasa Suenaga <yasuenag@gmail.com>
---
tools/hv/hv_fcopy_uio_daemon.c | 36 +++++++++++++---------------------
1 file changed, 14 insertions(+), 22 deletions(-)

diff --git a/tools/hv/hv_fcopy_uio_daemon.c b/tools/hv/hv_fcopy_uio_daemon.c
index 0198321d1..85ec21696 100644
--- a/tools/hv/hv_fcopy_uio_daemon.c
+++ b/tools/hv/hv_fcopy_uio_daemon.c
@@ -62,8 +62,10 @@ static int hv_fcopy_create_file(char *file_name, char *path_name, __u32 flags)

filesize = 0;
p = path_name;
- snprintf(target_fname, sizeof(target_fname), "%s/%s",
- path_name, file_name);
+ if (snprintf(target_fname, sizeof(target_fname), "%s/%s", path_name, file_name) >= sizeof(target_fname)) {
+ /* target file name is too long */
+ goto done;
+ }

/*
* Check to see if the path is already in place; if not,
@@ -273,6 +275,8 @@ static void wcstoutf8(char *dest, const __u16 *src, size_t dest_size)
while (len < dest_size) {
if (src[len] < 0x80)
dest[len++] = (char)(*src++);
+ else if (src[len] == '0')
+ break;
else
dest[len++] = 'X';
}
@@ -282,27 +286,15 @@ static void wcstoutf8(char *dest, const __u16 *src, size_t dest_size)

static int hv_fcopy_start(struct hv_start_fcopy *smsg_in)
{
- setlocale(LC_ALL, "en_US.utf8");
- size_t file_size, path_size;
- char *file_name, *path_name;
- char *in_file_name = (char *)smsg_in->file_name;
- char *in_path_name = (char *)smsg_in->path_name;
-
- file_size = wcstombs(NULL, (const wchar_t *restrict)in_file_name, 0) + 1;
- path_size = wcstombs(NULL, (const wchar_t *restrict)in_path_name, 0) + 1;
-
- file_name = (char *)malloc(file_size * sizeof(char));
- path_name = (char *)malloc(path_size * sizeof(char));
-
- if (!file_name || !path_name) {
- free(file_name);
- free(path_name);
- syslog(LOG_ERR, "Can't allocate memory for file name and/or path name");
- return HV_E_FAIL;
- }
+ /*
+ * file_name and path_name should have same length with appropriate
+ * member of hv_start_fcopy.
+ */
+ char file_name[W_MAX_PATH], path_name[W_MAX_PATH];

- wcstoutf8(file_name, (__u16 *)in_file_name, file_size);
- wcstoutf8(path_name, (__u16 *)in_path_name, path_size);
+ setlocale(LC_ALL, "en_US.utf8");
+ wcstoutf8(file_name, smsg_in->file_name, W_MAX_PATH - 1);
+ wcstoutf8(path_name, smsg_in->path_name, W_MAX_PATH - 1);

return hv_fcopy_create_file(file_name, path_name, smsg_in->copy_flags);
}
--
2.49.0