fs: port privilege checking helpers to const mnt_idmap

Convert to const struct mnt_idmap.

A mount's idmapping is immutable. The only thing that is allowed to be
modified afterwards is the reference count and that is hidden behind
mnt_idmap_get() and mnt_idmap_put(). Everything else only ever reads
from the idmapping. This is the same model that struct cred uses and the
idmapping is also rather sensitive.

So make the idmap argument const wherever we can. The conversion is done
from the bottom up so callers can continue to pass a non-const pointer
to a const parameter until the conversion is finished.

No functional changes.

Link: https://patch.msgid.link/20260901-work-idmap-const-v1-8-54ccd48e100b@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Seth Forshee <sforshee@kernel.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

3 files changed, 7 insertions, 7 deletions

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 37db92b3d6f8..c39a2bbefc47 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -181,9 +181,9 @@ static inline bool ns_capable_setid(struct user_namespace *ns, int cap)
 }
 #endif /* CONFIG_MULTIUSER */
 bool privileged_wrt_inode_uidgid(struct user_namespace *ns,
-				 struct mnt_idmap *idmap,
+				 const struct mnt_idmap *idmap,
 				 const struct inode *inode);
-bool capable_wrt_inode_uidgid(struct mnt_idmap *idmap,
+bool capable_wrt_inode_uidgid(const struct mnt_idmap *idmap,
 			      const struct inode *inode, int cap);
 extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
 extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 154f2c976a0a..7c82d7aaa775 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1835,7 +1835,7 @@ void inode_init_owner(struct mnt_idmap *idmap, struct inode *inode,
 extern bool may_open_dev(const struct path *path);
 umode_t mode_strip_sgid(struct mnt_idmap *idmap,
 			const struct inode *dir, umode_t mode);
-bool in_group_or_capable(struct mnt_idmap *idmap,
+bool in_group_or_capable(const struct mnt_idmap *idmap,
 			 const struct inode *inode, vfsgid_t vfsgid);
 
 /*
@@ -3045,9 +3045,9 @@ static inline struct inode *new_inode_pseudo(struct super_block *sb)
 }
 extern struct inode *new_inode(struct super_block *sb);
 extern void free_inode_nonrcu(struct inode *inode);
-extern int setattr_should_drop_suidgid(struct mnt_idmap *, struct inode *);
+extern int setattr_should_drop_suidgid(const struct mnt_idmap *, struct inode *);
 extern int file_remove_privs(struct file *);
-int setattr_should_drop_sgid(struct mnt_idmap *idmap,
+int setattr_should_drop_sgid(const struct mnt_idmap *idmap,
 			     const struct inode *inode);
 
 /*
@@ -3401,7 +3401,7 @@ int may_setattr(struct mnt_idmap *idmap, struct inode *inode,
 		unsigned int ia_valid);
 int setattr_prepare(struct mnt_idmap *, struct dentry *, struct iattr *);
 extern int inode_newsize_ok(const struct inode *, loff_t offset);
-void setattr_copy(struct mnt_idmap *, struct inode *inode,
+void setattr_copy(const struct mnt_idmap *, struct inode *inode,
 		  const struct iattr *attr);
 
 extern int file_update_time(struct file *file);
diff --git a/include/linux/security.h b/include/linux/security.h
index 153e9043058f..4598a13657ee 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -185,7 +185,7 @@ extern int cap_capset(struct cred *new, const struct cred *old,
 extern int cap_bprm_creds_from_file(struct linux_binprm *bprm, const struct file *file);
 int cap_inode_setxattr(struct dentry *dentry, const char *name,
 		       const void *value, size_t size, int flags);
-int cap_inode_removexattr(struct mnt_idmap *idmap,
+int cap_inode_removexattr(const struct mnt_idmap *idmap,
 			  struct dentry *dentry, const char *name);
 int cap_inode_need_killpriv(struct dentry *dentry);
 int cap_inode_killpriv(struct mnt_idmap *idmap, struct dentry *dentry);