From: Harald Hoyer <[email protected]>
path_is_mount_point() compares the mount_id of a directory and the
mount_id of the parent directory. When following symlinks, the function
to get the parent directory does not take the symlink into account.
/bin -> /usr/bin with /usr being a mountpoint:
mount_id of /bin with AT_SYMLINK_FOLLOW != mount_id of /
---
V2 with openat and all relative
V3 with _cleanup_close_
src/shared/path-util.c | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)
diff --git a/src/shared/path-util.c b/src/shared/path-util.c
index b9db7f1..5b7fed5 100644
--- a/src/shared/path-util.c
+++ b/src/shared/path-util.c
@@ -456,9 +456,9 @@ int path_is_mount_point(const char *t, bool allow_symlink) {
union file_handle_union h = FILE_HANDLE_INIT;
int mount_id = -1, mount_id_parent = -1;
- _cleanup_free_ char *parent = NULL;
struct stat a, b;
int r;
+ _cleanup_close_ int fd = -1;
bool nosupp = false;
/* We are not actually interested in the file handles, but
@@ -468,7 +468,15 @@ int path_is_mount_point(const char *t, bool allow_symlink)
{
if (path_equal(t, "/"))
return 1;
- r = name_to_handle_at(AT_FDCWD, t, &h.handle, &mount_id, allow_symlink
? AT_SYMLINK_FOLLOW : 0);
+ fd = openat(AT_FDCWD, t,
O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|(allow_symlink ? 0 : O_PATH));
+ if (fd < 0) {
+ if (errno == ENOENT)
+ return 0;
+
+ return -errno;
+ }
+
+ r = name_to_handle_at(fd, "", &h.handle, &mount_id, AT_EMPTY_PATH);
if (r < 0) {
if (errno == ENOSYS)
/* This kernel does not support name_to_handle_at()
@@ -485,12 +493,9 @@ int path_is_mount_point(const char *t, bool allow_symlink)
{
return -errno;
}
- r = path_get_parent(t, &parent);
- if (r < 0)
- return r;
h.handle.handle_bytes = MAX_HANDLE_SZ;
- r = name_to_handle_at(AT_FDCWD, parent, &h.handle, &mount_id_parent,
AT_SYMLINK_FOLLOW);
+ r = name_to_handle_at(fd, "..", &h.handle, &mount_id_parent, 0);
if (r < 0)
if (errno == EOPNOTSUPP)
if (nosupp)
@@ -509,10 +514,7 @@ int path_is_mount_point(const char *t, bool allow_symlink)
{
return mount_id != mount_id_parent;
fallback:
- if (allow_symlink)
- r = stat(t, &a);
- else
- r = lstat(t, &a);
+ r = fstatat(fd, "", &a, AT_EMPTY_PATH);
if (r < 0) {
if (errno == ENOENT)
@@ -521,14 +523,8 @@ fallback:
return -errno;
}
- free(parent);
- parent = NULL;
-
- r = path_get_parent(t, &parent);
- if (r < 0)
- return r;
- r = stat(parent, &b);
+ r = fstatat(fd, "..", &b, 0);
if (r < 0)
return -errno;
--
2.3.0
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