T: git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping.git
F: Documentation/filesystems/idmappings.rst
F: tools/testing/selftests/mount_setattr/
-F: include/linux/mnt_idmapping.h
+F: include/linux/mnt_idmapping.*
IDT VersaClock 5 CLOCK DRIVER
M: Luca Ceresoli <luca@lucaceresoli.net>
pnode.o splice.o sync.o utimes.o d_path.o \
stack.o fs_struct.o statfs.o fs_pin.o nsfs.o \
fs_types.o fs_context.o fs_parser.o fsopen.o init.o \
- kernel_read_file.o remap_range.o
+ kernel_read_file.o mnt_idmapping.o remap_range.o
ifeq ($(CONFIG_BLOCK),y)
obj-y += buffer.o direct-io.o mpage.o
struct mount;
struct shrink_control;
struct fs_context;
-struct user_namespace;
struct pipe_inode_info;
struct iov_iter;
+struct mnt_idmap;
/*
* block/bdev.c
*/
int setattr_should_drop_sgid(struct mnt_idmap *idmap,
const struct inode *inode);
+struct mnt_idmap *alloc_mnt_idmap(struct user_namespace *mnt_userns);
+struct mnt_idmap *mnt_idmap_get(struct mnt_idmap *idmap);
+void mnt_idmap_put(struct mnt_idmap *idmap);
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Christian Brauner <brauner@kernel.org> */
+
+#include <linux/cred.h>
+#include <linux/fs.h>
+#include <linux/mnt_idmapping.h>
+#include <linux/slab.h>
+#include <linux/user_namespace.h>
+
+#include "internal.h"
+
+struct mnt_idmap {
+ struct user_namespace *owner;
+ refcount_t count;
+};
+
+/*
+ * Carries the initial idmapping of 0:0:4294967295 which is an identity
+ * mapping. This means that {g,u}id 0 is mapped to {g,u}id 0, {g,u}id 1 is
+ * mapped to {g,u}id 1, [...], {g,u}id 1000 to {g,u}id 1000, [...].
+ */
+struct mnt_idmap nop_mnt_idmap = {
+ .owner = &init_user_ns,
+ .count = REFCOUNT_INIT(1),
+};
+EXPORT_SYMBOL_GPL(nop_mnt_idmap);
+
+/**
+ * check_fsmapping - check whether an mount idmapping is allowed
+ * @idmap: idmap of the relevent mount
+ * @sb: super block of the filesystem
+ *
+ * Return: true if @idmap is allowed, false if not.
+ */
+bool check_fsmapping(const struct mnt_idmap *idmap,
+ const struct super_block *sb)
+{
+ return idmap->owner != sb->s_user_ns;
+}
+
+/**
+ * initial_idmapping - check whether this is the initial mapping
+ * @ns: idmapping to check
+ *
+ * Check whether this is the initial mapping, mapping 0 to 0, 1 to 1,
+ * [...], 1000 to 1000 [...].
+ *
+ * Return: true if this is the initial mapping, false if not.
+ */
+static inline bool initial_idmapping(const struct user_namespace *ns)
+{
+ return ns == &init_user_ns;
+}
+
+/**
+ * no_idmapping - check whether we can skip remapping a kuid/gid
+ * @mnt_userns: the mount's idmapping
+ * @fs_userns: the filesystem's idmapping
+ *
+ * This function can be used to check whether a remapping between two
+ * idmappings is required.
+ * An idmapped mount is a mount that has an idmapping attached to it that
+ * is different from the filsystem's idmapping and the initial idmapping.
+ * If the initial mapping is used or the idmapping of the mount and the
+ * filesystem are identical no remapping is required.
+ *
+ * Return: true if remapping can be skipped, false if not.
+ */
+static inline bool no_idmapping(const struct user_namespace *mnt_userns,
+ const struct user_namespace *fs_userns)
+{
+ return initial_idmapping(mnt_userns) || mnt_userns == fs_userns;
+}
+
+/**
+ * make_vfsuid - map a filesystem kuid according to an idmapping
+ * @idmap: the mount's idmapping
+ * @fs_userns: the filesystem's idmapping
+ * @kuid : kuid to be mapped
+ *
+ * Take a @kuid and remap it from @fs_userns into @idmap. Use this
+ * function when preparing a @kuid to be reported to userspace.
+ *
+ * If no_idmapping() determines that this is not an idmapped mount we can
+ * simply return @kuid unchanged.
+ * If initial_idmapping() tells us that the filesystem is not mounted with an
+ * idmapping we know the value of @kuid won't change when calling
+ * from_kuid() so we can simply retrieve the value via __kuid_val()
+ * directly.
+ *
+ * Return: @kuid mapped according to @idmap.
+ * If @kuid has no mapping in either @idmap or @fs_userns INVALID_UID is
+ * returned.
+ */
+
+vfsuid_t make_vfsuid(struct mnt_idmap *idmap,
+ struct user_namespace *fs_userns,
+ kuid_t kuid)
+{
+ uid_t uid;
+ struct user_namespace *mnt_userns = idmap->owner;
+
+ if (no_idmapping(mnt_userns, fs_userns))
+ return VFSUIDT_INIT(kuid);
+ if (initial_idmapping(fs_userns))
+ uid = __kuid_val(kuid);
+ else
+ uid = from_kuid(fs_userns, kuid);
+ if (uid == (uid_t)-1)
+ return INVALID_VFSUID;
+ return VFSUIDT_INIT(make_kuid(mnt_userns, uid));
+}
+EXPORT_SYMBOL_GPL(make_vfsuid);
+
+/**
+ * make_vfsgid - map a filesystem kgid according to an idmapping
+ * @idmap: the mount's idmapping
+ * @fs_userns: the filesystem's idmapping
+ * @kgid : kgid to be mapped
+ *
+ * Take a @kgid and remap it from @fs_userns into @idmap. Use this
+ * function when preparing a @kgid to be reported to userspace.
+ *
+ * If no_idmapping() determines that this is not an idmapped mount we can
+ * simply return @kgid unchanged.
+ * If initial_idmapping() tells us that the filesystem is not mounted with an
+ * idmapping we know the value of @kgid won't change when calling
+ * from_kgid() so we can simply retrieve the value via __kgid_val()
+ * directly.
+ *
+ * Return: @kgid mapped according to @idmap.
+ * If @kgid has no mapping in either @idmap or @fs_userns INVALID_GID is
+ * returned.
+ */
+vfsgid_t make_vfsgid(struct mnt_idmap *idmap,
+ struct user_namespace *fs_userns, kgid_t kgid)
+{
+ gid_t gid;
+ struct user_namespace *mnt_userns = idmap->owner;
+
+ if (no_idmapping(mnt_userns, fs_userns))
+ return VFSGIDT_INIT(kgid);
+ if (initial_idmapping(fs_userns))
+ gid = __kgid_val(kgid);
+ else
+ gid = from_kgid(fs_userns, kgid);
+ if (gid == (gid_t)-1)
+ return INVALID_VFSGID;
+ return VFSGIDT_INIT(make_kgid(mnt_userns, gid));
+}
+EXPORT_SYMBOL_GPL(make_vfsgid);
+
+/**
+ * from_vfsuid - map a vfsuid into the filesystem idmapping
+ * @idmap: the mount's idmapping
+ * @fs_userns: the filesystem's idmapping
+ * @vfsuid : vfsuid to be mapped
+ *
+ * Map @vfsuid into the filesystem idmapping. This function has to be used in
+ * order to e.g. write @vfsuid to inode->i_uid.
+ *
+ * Return: @vfsuid mapped into the filesystem idmapping
+ */
+kuid_t from_vfsuid(struct mnt_idmap *idmap,
+ struct user_namespace *fs_userns, vfsuid_t vfsuid)
+{
+ uid_t uid;
+ struct user_namespace *mnt_userns = idmap->owner;
+
+ if (no_idmapping(mnt_userns, fs_userns))
+ return AS_KUIDT(vfsuid);
+ uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid));
+ if (uid == (uid_t)-1)
+ return INVALID_UID;
+ if (initial_idmapping(fs_userns))
+ return KUIDT_INIT(uid);
+ return make_kuid(fs_userns, uid);
+}
+EXPORT_SYMBOL_GPL(from_vfsuid);
+
+/**
+ * from_vfsgid - map a vfsgid into the filesystem idmapping
+ * @idmap: the mount's idmapping
+ * @fs_userns: the filesystem's idmapping
+ * @vfsgid : vfsgid to be mapped
+ *
+ * Map @vfsgid into the filesystem idmapping. This function has to be used in
+ * order to e.g. write @vfsgid to inode->i_gid.
+ *
+ * Return: @vfsgid mapped into the filesystem idmapping
+ */
+kgid_t from_vfsgid(struct mnt_idmap *idmap,
+ struct user_namespace *fs_userns, vfsgid_t vfsgid)
+{
+ gid_t gid;
+ struct user_namespace *mnt_userns = idmap->owner;
+
+ if (no_idmapping(mnt_userns, fs_userns))
+ return AS_KGIDT(vfsgid);
+ gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid));
+ if (gid == (gid_t)-1)
+ return INVALID_GID;
+ if (initial_idmapping(fs_userns))
+ return KGIDT_INIT(gid);
+ return make_kgid(fs_userns, gid);
+}
+EXPORT_SYMBOL_GPL(from_vfsgid);
+
+#ifdef CONFIG_MULTIUSER
+/**
+ * vfsgid_in_group_p() - check whether a vfsuid matches the caller's groups
+ * @vfsgid: the mnt gid to match
+ *
+ * This function can be used to determine whether @vfsuid matches any of the
+ * caller's groups.
+ *
+ * Return: 1 if vfsuid matches caller's groups, 0 if not.
+ */
+int vfsgid_in_group_p(vfsgid_t vfsgid)
+{
+ return in_group_p(AS_KGIDT(vfsgid));
+}
+#else
+int vfsgid_in_group_p(vfsgid_t vfsgid)
+{
+ return 1;
+}
+#endif
+EXPORT_SYMBOL_GPL(vfsgid_in_group_p);
+
+struct mnt_idmap *alloc_mnt_idmap(struct user_namespace *mnt_userns)
+{
+ struct mnt_idmap *idmap;
+
+ idmap = kzalloc(sizeof(struct mnt_idmap), GFP_KERNEL_ACCOUNT);
+ if (!idmap)
+ return ERR_PTR(-ENOMEM);
+
+ idmap->owner = get_user_ns(mnt_userns);
+ refcount_set(&idmap->count, 1);
+ return idmap;
+}
+
+/**
+ * mnt_idmap_get - get a reference to an idmapping
+ * @idmap: the idmap to bump the reference on
+ *
+ * If @idmap is not the @nop_mnt_idmap bump the reference count.
+ *
+ * Return: @idmap with reference count bumped if @not_mnt_idmap isn't passed.
+ */
+struct mnt_idmap *mnt_idmap_get(struct mnt_idmap *idmap)
+{
+ if (idmap != &nop_mnt_idmap)
+ refcount_inc(&idmap->count);
+
+ return idmap;
+}
+
+/**
+ * mnt_idmap_put - put a reference to an idmapping
+ * @idmap: the idmap to put the reference on
+ *
+ * If this is a non-initial idmapping, put the reference count when a mount is
+ * released and free it if we're the last user.
+ */
+void mnt_idmap_put(struct mnt_idmap *idmap)
+{
+ if (idmap != &nop_mnt_idmap && refcount_dec_and_test(&idmap->count)) {
+ put_user_ns(idmap->owner);
+ kfree(idmap);
+ }
+}
static HLIST_HEAD(unmounted); /* protected by namespace_sem */
static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
-struct mnt_idmap {
- struct user_namespace *owner;
- refcount_t count;
-};
-
-/*
- * Carries the initial idmapping of 0:0:4294967295 which is an identity
- * mapping. This means that {g,u}id 0 is mapped to {g,u}id 0, {g,u}id 1 is
- * mapped to {g,u}id 1, [...], {g,u}id 1000 to {g,u}id 1000, [...].
- */
-struct mnt_idmap nop_mnt_idmap = {
- .owner = &init_user_ns,
- .count = REFCOUNT_INIT(1),
-};
-EXPORT_SYMBOL_GPL(nop_mnt_idmap);
-
struct mount_kattr {
unsigned int attr_set;
unsigned int attr_clr;
#endif
}
-/**
- * mnt_idmap_owner - retrieve owner of the mount's idmapping
- * @idmap: mount idmapping
- *
- * This helper will go away once the conversion to use struct mnt_idmap
- * everywhere has finished at which point the helper will be unexported.
- *
- * Only code that needs to perform permission checks based on the owner of the
- * idmapping will get access to it. All other code will solely rely on
- * idmappings. This will get us type safety so it's impossible to conflate
- * filesystems idmappings with mount idmappings.
- *
- * Return: The owner of the idmapping.
- */
-struct user_namespace *mnt_idmap_owner(const struct mnt_idmap *idmap)
-{
- return idmap->owner;
-}
-EXPORT_SYMBOL_GPL(mnt_idmap_owner);
-
-/**
- * alloc_mnt_idmap - allocate a new idmapping for the mount
- * @mnt_userns: owning userns of the idmapping
- *
- * Allocate a new struct mnt_idmap which carries the idmapping of the mount.
- *
- * Return: On success a new idmap, on error an error pointer is returned.
- */
-static struct mnt_idmap *alloc_mnt_idmap(struct user_namespace *mnt_userns)
-{
- struct mnt_idmap *idmap;
-
- idmap = kzalloc(sizeof(struct mnt_idmap), GFP_KERNEL_ACCOUNT);
- if (!idmap)
- return ERR_PTR(-ENOMEM);
-
- idmap->owner = get_user_ns(mnt_userns);
- refcount_set(&idmap->count, 1);
- return idmap;
-}
-
-/**
- * mnt_idmap_get - get a reference to an idmapping
- * @idmap: the idmap to bump the reference on
- *
- * If @idmap is not the @nop_mnt_idmap bump the reference count.
- *
- * Return: @idmap with reference count bumped if @not_mnt_idmap isn't passed.
- */
-static inline struct mnt_idmap *mnt_idmap_get(struct mnt_idmap *idmap)
-{
- if (idmap != &nop_mnt_idmap)
- refcount_inc(&idmap->count);
-
- return idmap;
-}
-
-/**
- * mnt_idmap_put - put a reference to an idmapping
- * @idmap: the idmap to put the reference on
- *
- * If this is a non-initial idmapping, put the reference count when a mount is
- * released and free it if we're the last user.
- */
-static inline void mnt_idmap_put(struct mnt_idmap *idmap)
-{
- if (idmap != &nop_mnt_idmap && refcount_dec_and_test(&idmap->count)) {
- put_user_ns(idmap->owner);
- kfree(idmap);
- }
-}
-
static struct mount *alloc_vfsmnt(const char *name)
{
struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
* Creating an idmapped mount with the filesystem wide idmapping
* doesn't make sense so block that. We don't allow mushy semantics.
*/
- if (mnt_idmap_owner(kattr->mnt_idmap) == fs_userns)
+ if (!check_fsmapping(kattr->mnt_idmap, m->mnt_sb))
return -EINVAL;
/*
* result.
*/
mnt_userns = container_of(ns, struct user_namespace, ns);
- if (initial_idmapping(mnt_userns)) {
+ if (mnt_userns == &init_user_ns) {
err = -EPERM;
goto out_fput;
}
#define AS_KUIDT(val) (kuid_t){ __vfsuid_val(val) }
#define AS_KGIDT(val) (kgid_t){ __vfsgid_val(val) }
-#ifdef CONFIG_MULTIUSER
-/**
- * vfsgid_in_group_p() - check whether a vfsuid matches the caller's groups
- * @vfsgid: the mnt gid to match
- *
- * This function can be used to determine whether @vfsuid matches any of the
- * caller's groups.
- *
- * Return: 1 if vfsuid matches caller's groups, 0 if not.
- */
-static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
-{
- return in_group_p(AS_KGIDT(vfsgid));
-}
-#else
-static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
-{
- return 1;
-}
-#endif
+int vfsgid_in_group_p(vfsgid_t vfsgid);
-/**
- * initial_idmapping - check whether this is the initial mapping
- * @ns: idmapping to check
- *
- * Check whether this is the initial mapping, mapping 0 to 0, 1 to 1,
- * [...], 1000 to 1000 [...].
- *
- * Return: true if this is the initial mapping, false if not.
- */
-static inline bool initial_idmapping(const struct user_namespace *ns)
-{
- return ns == &init_user_ns;
-}
+vfsuid_t make_vfsuid(struct mnt_idmap *idmap,
+ struct user_namespace *fs_userns, kuid_t kuid);
-/**
- * no_idmapping - check whether we can skip remapping a kuid/gid
- * @mnt_userns: the mount's idmapping
- * @fs_userns: the filesystem's idmapping
- *
- * This function can be used to check whether a remapping between two
- * idmappings is required.
- * An idmapped mount is a mount that has an idmapping attached to it that
- * is different from the filsystem's idmapping and the initial idmapping.
- * If the initial mapping is used or the idmapping of the mount and the
- * filesystem are identical no remapping is required.
- *
- * Return: true if remapping can be skipped, false if not.
- */
-static inline bool no_idmapping(const struct user_namespace *mnt_userns,
- const struct user_namespace *fs_userns)
-{
- return initial_idmapping(mnt_userns) || mnt_userns == fs_userns;
-}
+vfsgid_t make_vfsgid(struct mnt_idmap *idmap,
+ struct user_namespace *fs_userns, kgid_t kgid);
-/**
- * make_vfsuid - map a filesystem kuid into a mnt_userns
- * @idmap: the mount's idmapping
- * @fs_userns: the filesystem's idmapping
- * @kuid : kuid to be mapped
- *
- * Take a @kuid and remap it from @fs_userns into @mnt_userns. Use this
- * function when preparing a @kuid to be reported to userspace.
- *
- * If no_idmapping() determines that this is not an idmapped mount we can
- * simply return @kuid unchanged.
- * If initial_idmapping() tells us that the filesystem is not mounted with an
- * idmapping we know the value of @kuid won't change when calling
- * from_kuid() so we can simply retrieve the value via __kuid_val()
- * directly.
- *
- * Return: @kuid mapped according to @mnt_userns.
- * If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
- * returned.
- */
+kuid_t from_vfsuid(struct mnt_idmap *idmap,
+ struct user_namespace *fs_userns, vfsuid_t vfsuid);
-static inline vfsuid_t make_vfsuid(struct mnt_idmap *idmap,
- struct user_namespace *fs_userns,
- kuid_t kuid)
-{
- uid_t uid;
- struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-
- if (no_idmapping(mnt_userns, fs_userns))
- return VFSUIDT_INIT(kuid);
- if (initial_idmapping(fs_userns))
- uid = __kuid_val(kuid);
- else
- uid = from_kuid(fs_userns, kuid);
- if (uid == (uid_t)-1)
- return INVALID_VFSUID;
- return VFSUIDT_INIT(make_kuid(mnt_userns, uid));
-}
-
-/**
- * make_vfsgid - map a filesystem kgid into a mnt_userns
- * @idmap: the mount's idmapping
- * @fs_userns: the filesystem's idmapping
- * @kgid : kgid to be mapped
- *
- * Take a @kgid and remap it from @fs_userns into @mnt_userns. Use this
- * function when preparing a @kgid to be reported to userspace.
- *
- * If no_idmapping() determines that this is not an idmapped mount we can
- * simply return @kgid unchanged.
- * If initial_idmapping() tells us that the filesystem is not mounted with an
- * idmapping we know the value of @kgid won't change when calling
- * from_kgid() so we can simply retrieve the value via __kgid_val()
- * directly.
- *
- * Return: @kgid mapped according to @mnt_userns.
- * If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
- * returned.
- */
-
-static inline vfsgid_t make_vfsgid(struct mnt_idmap *idmap,
- struct user_namespace *fs_userns,
- kgid_t kgid)
-{
- gid_t gid;
- struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-
- if (no_idmapping(mnt_userns, fs_userns))
- return VFSGIDT_INIT(kgid);
- if (initial_idmapping(fs_userns))
- gid = __kgid_val(kgid);
- else
- gid = from_kgid(fs_userns, kgid);
- if (gid == (gid_t)-1)
- return INVALID_VFSGID;
- return VFSGIDT_INIT(make_kgid(mnt_userns, gid));
-}
-
-/**
- * from_vfsuid - map a vfsuid into the filesystem idmapping
- * @idmap: the mount's idmapping
- * @fs_userns: the filesystem's idmapping
- * @vfsuid : vfsuid to be mapped
- *
- * Map @vfsuid into the filesystem idmapping. This function has to be used in
- * order to e.g. write @vfsuid to inode->i_uid.
- *
- * Return: @vfsuid mapped into the filesystem idmapping
- */
-static inline kuid_t from_vfsuid(struct mnt_idmap *idmap,
- struct user_namespace *fs_userns,
- vfsuid_t vfsuid)
-{
- uid_t uid;
- struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-
- if (no_idmapping(mnt_userns, fs_userns))
- return AS_KUIDT(vfsuid);
- uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid));
- if (uid == (uid_t)-1)
- return INVALID_UID;
- if (initial_idmapping(fs_userns))
- return KUIDT_INIT(uid);
- return make_kuid(fs_userns, uid);
-}
+kgid_t from_vfsgid(struct mnt_idmap *idmap,
+ struct user_namespace *fs_userns, vfsgid_t vfsgid);
/**
* vfsuid_has_fsmapping - check whether a vfsuid maps into the filesystem
}
/**
- * from_vfsgid - map a vfsgid into the filesystem idmapping
- * @idmap: the mount's idmapping
- * @fs_userns: the filesystem's idmapping
- * @vfsgid : vfsgid to be mapped
- *
- * Map @vfsgid into the filesystem idmapping. This function has to be used in
- * order to e.g. write @vfsgid to inode->i_gid.
- *
- * Return: @vfsgid mapped into the filesystem idmapping
- */
-static inline kgid_t from_vfsgid(struct mnt_idmap *idmap,
- struct user_namespace *fs_userns,
- vfsgid_t vfsgid)
-{
- gid_t gid;
- struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-
- if (no_idmapping(mnt_userns, fs_userns))
- return AS_KGIDT(vfsgid);
- gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid));
- if (gid == (gid_t)-1)
- return INVALID_GID;
- if (initial_idmapping(fs_userns))
- return KGIDT_INIT(gid);
- return make_kgid(fs_userns, gid);
-}
-
-/**
* vfsgid_has_fsmapping - check whether a vfsgid maps into the filesystem
* @idmap: the mount's idmapping
* @fs_userns: the filesystem's idmapping
return from_vfsgid(idmap, fs_userns, VFSGIDT_INIT(current_fsgid()));
}
+bool check_fsmapping(const struct mnt_idmap *idmap,
+ const struct super_block *sb);
+
#endif /* _LINUX_MNT_IDMAPPING_H */
struct mnt_idmap *mnt_idmap;
} __randomize_layout;
-struct user_namespace *mnt_idmap_owner(const struct mnt_idmap *idmap);
static inline struct mnt_idmap *mnt_idmap(const struct vfsmount *mnt)
{
/* Pairs with smp_store_release() in do_idmap_mount(). */
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