Provide a type-safe interface for retrieving filesystem capabilities and
a generic implementation suitable for most filesystems. Also add an
internal interface, __vfs_get_fscaps(), which skips security checks for
later use from the capability code.
Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@xxxxxxxxxx>
---
fs/xattr.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 4 ++++
2 files changed, 70 insertions(+)
diff --git a/fs/xattr.c b/fs/xattr.c
index 09d927603433..3abaf9bef0a5 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -181,6 +181,72 @@ xattr_supports_user_prefix(struct inode *inode)
}
EXPORT_SYMBOL(xattr_supports_user_prefix);
+static int generic_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry,
+ struct vfs_caps *caps)
+{
+ struct inode *inode = d_inode(dentry);
+ struct vfs_ns_cap_data *nscaps = NULL;
+ int ret;
+
+ ret = (int)vfs_getxattr_alloc(idmap, dentry, XATTR_NAME_CAPS,
+ (char **)&nscaps, 0, GFP_NOFS);
+
+ if (ret >= 0)
+ ret = vfs_caps_from_xattr(idmap, i_user_ns(inode), caps, nscaps, ret);
+
+ kfree(nscaps);
+ return ret;
+}
+
+/**
+ * __vfs_get_fscaps - get filesystem capabilities without security checks
+ * @idmap: idmap of the mount the inode was found from
+ * @dentry: the dentry from which to get filesystem capabilities
+ * @caps: storage in which to return the filesystem capabilities
+ *
+ * This function gets the filesystem capabilities for the dentry and returns
+ * them in @caps. It does not perform security checks.
+ *
+ * Return: 0 on success, a negative errno on error.
+ */
+int __vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry,
+ struct vfs_caps *caps)
+{
+ struct inode *inode = d_inode(dentry);
+
+ if (inode->i_op->get_fscaps)
+ return inode->i_op->get_fscaps(idmap, dentry, caps);
+ return generic_get_fscaps(idmap, dentry, caps);
+}
+
+/**
+ * vfs_get_fscaps - get filesystem capabilities
+ * @idmap: idmap of the mount the inode was found from
+ * @dentry: the dentry from which to get filesystem capabilities
+ * @caps: storage in which to return the filesystem capabilities
+ *
+ * This function gets the filesystem capabilities for the dentry and returns
+ * them in @caps.
+ *
+ * Return: 0 on success, a negative errno on error.
+ */
+int vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry,
+ struct vfs_caps *caps)
+{
+ int error;
+
+ /*
+ * The VFS has no restrictions on reading security.* xattrs, so
+ * xattr_permission() isn't needed. Only LSMs get a say.
+ */
+ error = security_inode_getxattr(dentry, XATTR_NAME_CAPS);
+ if (error)
+ return error;
+
+ return __vfs_get_fscaps(idmap, dentry, caps);
+}
+EXPORT_SYMBOL(vfs_get_fscaps);
+
int
__vfs_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
struct inode *inode, const char *name, const void *value,
diff --git a/include/linux/fs.h b/include/linux/fs.h
index a0a77f67b999..e25b39e4017a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2055,6 +2055,10 @@ extern int vfs_dedupe_file_range(struct file *file,
extern loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
struct file *dst_file, loff_t dst_pos,
loff_t len, unsigned int remap_flags);
+extern int __vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry,
+ struct vfs_caps *caps);
+extern int vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry,
+ struct vfs_caps *caps);
enum freeze_holder {
FREEZE_HOLDER_KERNEL = (1U << 0),
--
2.43.0
