Determining whether a path or file descriptor refers to a mountpoint (or
more precisely a mount root) is not trivial using current tools.
Add a flag to statx that indicates whether the path or fd refers to the
root of a mount or not.
Reported-by: Lennart Poettering <mzxreary@xxxxxxxxxxx>
Reported-by: J. Bruce Fields <bfields@xxxxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
---
fs/stat.c | 3 +++
include/uapi/linux/stat.h | 1 +
2 files changed, 4 insertions(+)
diff --git a/fs/stat.c b/fs/stat.c
index 3d88c99f7743..b9faa6cafafe 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -202,6 +202,9 @@ int vfs_statx(int dfd, const char __user *filename, int flags,
error = vfs_getattr(&path, stat, request_mask, flags);
stat->mnt_id = real_mount(path.mnt)->mnt_id;
stat->result_mask |= STATX_MNT_ID;
+ if (path.mnt->mnt_root == path.dentry)
+ stat->attributes |= STATX_ATTR_MOUNT_ROOT;
+ stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT;
path_put(&path);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index d81456247f10..6df9348bb277 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -181,6 +181,7 @@ struct statx {
#define STATX_ATTR_NODUMP 0x00000040 /* [I] File is not to be dumped */
#define STATX_ATTR_ENCRYPTED 0x00000800 /* [I] File requires key to decrypt in fs */
#define STATX_ATTR_AUTOMOUNT 0x00001000 /* Dir: Automount trigger */
+#define STATX_ATTR_MOUNT_ROOT 0x00002000 /* Root of a mount */
#define STATX_ATTR_VERITY 0x00100000 /* [I] Verity protected file */
--
2.21.1
