On 2024/07/16 19:54, Daniel P. Berrangé wrote:
On Tue, Jul 16, 2024 at 07:52:00PM +0900, Akihiko Odaki wrote:
On 2024/07/16 18:53, Daniel P. Berrangé wrote:
On Tue, Jul 16, 2024 at 04:27:31PM +0900, Akihiko Odaki wrote:
qemu_get_runtime_dir() returns a dynamically allocated directory path
that is appropriate for storing runtime files. It corresponds to "run"
directory in Unix.
With a tree-wide search, it was found that there are several cases
where such a functionality is implemented so let's have one as a common
utlity function.
A notable feature of qemu_get_runtime_dir() is that it uses
$XDG_RUNTIME_DIR if available. While the function is often called by
executables which requires root privileges, it is still possible that
they are called from a user without privilege to write the system
runtime directory. In fact, I decided to write this patch when I ran
virtiofsd in a Linux namespace created by a normal user and realized
it tries to write the system runtime directory, not writable in this
case. $XDG_RUNTIME_DIR should provide a writable directory in such
cases.
This function does not use qemu_get_local_state_dir() or its logic
for Windows. Actually the implementation of qemu_get_local_state_dir()
for Windows seems not right as it calls g_get_system_data_dirs(),
which refers to $XDG_DATA_DIRS. In Unix terminology, it is basically
"/usr/share", not "/var", which qemu_get_local_state_dir() is intended
to provide. Instead, this function try to use the following in order:
- $XDG_RUNTIME_DIR
- LocalAppData folder
- get_relocated_path(CONFIG_QEMU_LOCALSTATEDIR "/run")
This function does not use g_get_user_runtime_dir() either as it
falls back to g_get_user_cache_dir() when $XDG_DATA_DIRS is not
available. In the case, we rather use:
get_relocated_path(CONFIG_QEMU_LOCALSTATEDIR "/run")
Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com>
Message-Id: <20230921075425.16738-2-akihiko.od...@daynix.com>
---
include/qemu/osdep.h | 12 ++++++++++++
util/oslib-posix.c | 11 +++++++++++
util/oslib-win32.c | 26 ++++++++++++++++++++++++++
3 files changed, 49 insertions(+)
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 191916f38e6d..fe8609fc1375 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -670,6 +670,18 @@ void qemu_set_cloexec(int fd);
*/
char *qemu_get_local_state_dir(void);
+/**
+ * qemu_get_runtime_dir:
+ *
+ * Return a dynamically allocated directory path that is appropriate for
storing
+ * runtime files. It corresponds to "run" directory in Unix, and uses
+ * $XDG_RUNTIME_DIR if available.
+ *
+ * The caller is responsible for releasing the value returned with g_free()
+ * after use.
+ */
+char *qemu_get_runtime_dir(void);
+
/**
* qemu_getauxval:
* @type: the auxiliary vector key to lookup
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index e76441695bdc..9599509a9aa7 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -278,6 +278,17 @@ qemu_get_local_state_dir(void)
return get_relocated_path(CONFIG_QEMU_LOCALSTATEDIR);
}
+char *
+qemu_get_runtime_dir(void)
+{
+ char *env = getenv("XDG_RUNTIME_DIR");
+ if (env) {
+ return g_strdup(env);
+ }
+
+ return get_relocated_path(CONFIG_QEMU_LOCALSTATEDIR "/run");
+}
I'm not convinced this is the correct logic to be following.
In the cover letter you mention not using g_get_user_runtime_dir()
because it falls back to XDG_CACHE_HOME, and we need to fallback
to LOCALSTATEDIR/run. This is not right for normal users though,
where falling back to LOCALSTATEDIR/run is always wrong, as it
won't be writable - the g_get_user_runtime_dir() fallback is
desirable for non-root users.
It also checks LocalAppData, which should be usually available.
g_get_user_runtime_dir() is not a proper fallback in case neither of
XDG_RUNTIME_DIR and LocalAppData are available. g_get_user_cache_dir(),
which gets called by g_get_user_runtime_dir(), internally uses:
- XDG_CACHE_HOME or
- FOLDERID_InternetCache
g_get_user_cache_dir() just returns NULL if neither of them is available.
We can't expect XDG_CACHE_HOME is present when XDG_RUNTIME_DIR is missing.
FOLDERID_InternetCache points to %LOCALAPPDATA%\Microsoft\Windows\Temporary
Internet Files, according to:
https://learn.microsoft.com/en-us/windows/win32/shell/knownfolderid
So we can't expect FOLDERID_InternetCache is available when LocalAppData is
missing.
XDG_CACHE_HOME isn't required to be present. Glib will use a fallback
location if XDG_CACHE_HOME isn't set, and it will mkdir() the location
if it doesn't exist.
The fallback location is FOLDERID_InternetCache, which is not better
than looking at LocalAppData.
Regards,
Akihiko Odaki
