Link: https://lore.kernel.org/linux-fsdevel/20240904-baugrube-erhoben-b3c1c49a2645@brauner/ Suggested-by: Christian Brauner <brauner@xxxxxxxxxx> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx> --- fs/mnt_idmapping.c | 22 ++++++++++++++++++++-- include/linux/mnt_idmapping.h | 1 + 2 files changed, 21 insertions(+), 2 deletions(-) diff --git a/fs/mnt_idmapping.c b/fs/mnt_idmapping.c index 3c60f1eaca61..cbca6500848e 100644 --- a/fs/mnt_idmapping.c +++ b/fs/mnt_idmapping.c @@ -32,6 +32,15 @@ struct mnt_idmap nop_mnt_idmap = { }; EXPORT_SYMBOL_GPL(nop_mnt_idmap); +/* + * Carries the invalid idmapping of a full 0-4294967295 {g,u}id range. + * This means that all {g,u}ids are mapped to INVALID_VFS{G,U}ID. + */ +struct mnt_idmap invalid_mnt_idmap = { + .count = REFCOUNT_INIT(1), +}; +EXPORT_SYMBOL_GPL(invalid_mnt_idmap); + /** * initial_idmapping - check whether this is the initial mapping * @ns: idmapping to check @@ -75,6 +84,8 @@ vfsuid_t make_vfsuid(struct mnt_idmap *idmap, if (idmap == &nop_mnt_idmap) return VFSUIDT_INIT(kuid); + if (idmap == &invalid_mnt_idmap) + return INVALID_VFSUID; if (initial_idmapping(fs_userns)) uid = __kuid_val(kuid); else @@ -112,6 +123,8 @@ vfsgid_t make_vfsgid(struct mnt_idmap *idmap, if (idmap == &nop_mnt_idmap) return VFSGIDT_INIT(kgid); + if (idmap == &invalid_mnt_idmap) + return INVALID_VFSGID; if (initial_idmapping(fs_userns)) gid = __kgid_val(kgid); else @@ -140,6 +153,8 @@ kuid_t from_vfsuid(struct mnt_idmap *idmap, if (idmap == &nop_mnt_idmap) return AS_KUIDT(vfsuid); + if (idmap == &invalid_mnt_idmap) + return INVALID_UID; uid = map_id_up(&idmap->uid_map, __vfsuid_val(vfsuid)); if (uid == (uid_t)-1) return INVALID_UID; @@ -167,6 +182,8 @@ kgid_t from_vfsgid(struct mnt_idmap *idmap, if (idmap == &nop_mnt_idmap) return AS_KGIDT(vfsgid); + if (idmap == &invalid_mnt_idmap) + return INVALID_GID; gid = map_id_up(&idmap->gid_map, __vfsgid_val(vfsgid)); if (gid == (gid_t)-1) return INVALID_GID; @@ -296,7 +313,7 @@ struct mnt_idmap *alloc_mnt_idmap(struct user_namespace *mnt_userns) */ struct mnt_idmap *mnt_idmap_get(struct mnt_idmap *idmap) { - if (idmap != &nop_mnt_idmap) + if (idmap != &nop_mnt_idmap && idmap != &invalid_mnt_idmap) refcount_inc(&idmap->count); return idmap; @@ -312,7 +329,8 @@ EXPORT_SYMBOL_GPL(mnt_idmap_get); */ void mnt_idmap_put(struct mnt_idmap *idmap) { - if (idmap != &nop_mnt_idmap && refcount_dec_and_test(&idmap->count)) + if (idmap != &nop_mnt_idmap && idmap != &invalid_mnt_idmap && + refcount_dec_and_test(&idmap->count)) free_mnt_idmap(idmap); } EXPORT_SYMBOL_GPL(mnt_idmap_put); diff --git a/include/linux/mnt_idmapping.h b/include/linux/mnt_idmapping.h index cd4d5c8781f5..b1b219bc3422 100644 --- a/include/linux/mnt_idmapping.h +++ b/include/linux/mnt_idmapping.h @@ -9,6 +9,7 @@ struct mnt_idmap; struct user_namespace; extern struct mnt_idmap nop_mnt_idmap; +extern struct mnt_idmap invalid_mnt_idmap; extern struct user_namespace init_user_ns; typedef struct { -- 2.34.1
