diff options
| -rw-r--r-- | fs/mnt_idmapping.c | 106 | ||||
| -rw-r--r-- | include/linux/uidgid.h | 13 | ||||
| -rw-r--r-- | kernel/user_namespace.c | 4 |
3 files changed, 106 insertions, 17 deletions
diff --git a/fs/mnt_idmapping.c b/fs/mnt_idmapping.c index 35d78cb3c38a..64c5205e2b5e 100644 --- a/fs/mnt_idmapping.c +++ b/fs/mnt_idmapping.c @@ -9,8 +9,16 @@ #include "internal.h" +/* + * Outside of this file vfs{g,u}id_t are always created from k{g,u}id_t, + * never from raw values. These are just internal helpers. + */ +#define VFSUIDT_INIT_RAW(val) (vfsuid_t){ val } +#define VFSGIDT_INIT_RAW(val) (vfsgid_t){ val } + struct mnt_idmap { - struct user_namespace *owner; + struct uid_gid_map uid_map; + struct uid_gid_map gid_map; refcount_t count; }; @@ -20,7 +28,6 @@ struct mnt_idmap { * 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); @@ -65,7 +72,6 @@ vfsuid_t make_vfsuid(struct mnt_idmap *idmap, kuid_t kuid) { uid_t uid; - struct user_namespace *mnt_userns = idmap->owner; if (idmap == &nop_mnt_idmap) return VFSUIDT_INIT(kuid); @@ -75,7 +81,7 @@ vfsuid_t make_vfsuid(struct mnt_idmap *idmap, uid = from_kuid(fs_userns, kuid); if (uid == (uid_t)-1) return INVALID_VFSUID; - return VFSUIDT_INIT(make_kuid(mnt_userns, uid)); + return VFSUIDT_INIT_RAW(map_id_down(&idmap->uid_map, uid)); } EXPORT_SYMBOL_GPL(make_vfsuid); @@ -103,7 +109,6 @@ 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 (idmap == &nop_mnt_idmap) return VFSGIDT_INIT(kgid); @@ -113,7 +118,7 @@ vfsgid_t make_vfsgid(struct mnt_idmap *idmap, gid = from_kgid(fs_userns, kgid); if (gid == (gid_t)-1) return INVALID_VFSGID; - return VFSGIDT_INIT(make_kgid(mnt_userns, gid)); + return VFSGIDT_INIT_RAW(map_id_down(&idmap->gid_map, gid)); } EXPORT_SYMBOL_GPL(make_vfsgid); @@ -132,11 +137,10 @@ 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 (idmap == &nop_mnt_idmap) return AS_KUIDT(vfsuid); - uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid)); + uid = map_id_up(&idmap->uid_map, __vfsuid_val(vfsuid)); if (uid == (uid_t)-1) return INVALID_UID; if (initial_idmapping(fs_userns)) @@ -160,11 +164,10 @@ 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 (idmap == &nop_mnt_idmap) return AS_KGIDT(vfsgid); - gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid)); + gid = map_id_up(&idmap->gid_map, __vfsgid_val(vfsgid)); if (gid == (gid_t)-1) return INVALID_GID; if (initial_idmapping(fs_userns)) @@ -195,16 +198,91 @@ int vfsgid_in_group_p(vfsgid_t vfsgid) #endif EXPORT_SYMBOL_GPL(vfsgid_in_group_p); +static int copy_mnt_idmap(struct uid_gid_map *map_from, + struct uid_gid_map *map_to) +{ + struct uid_gid_extent *forward, *reverse; + u32 nr_extents = READ_ONCE(map_from->nr_extents); + /* Pairs with smp_wmb() when writing the idmapping. */ + smp_rmb(); + + /* + * Don't blindly copy @map_to into @map_from if nr_extents is + * smaller or equal to UID_GID_MAP_MAX_BASE_EXTENTS. Since we + * read @nr_extents someone could have written an idmapping and + * then we might end up with inconsistent data. So just don't do + * anything at all. + */ + if (nr_extents == 0) + return 0; + + /* + * Here we know that nr_extents is greater than zero which means + * a map has been written. Since idmappings can't be changed + * once they have been written we know that we can safely copy + * from @map_to into @map_from. + */ + + if (nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) { + *map_to = *map_from; + return 0; + } + + forward = kmemdup(map_from->forward, + nr_extents * sizeof(struct uid_gid_extent), + GFP_KERNEL_ACCOUNT); + if (!forward) + return -ENOMEM; + + reverse = kmemdup(map_from->reverse, + nr_extents * sizeof(struct uid_gid_extent), + GFP_KERNEL_ACCOUNT); + if (!reverse) { + kfree(forward); + return -ENOMEM; + } + + /* + * The idmapping isn't exposed anywhere so we don't need to care + * about ordering between extent pointers and @nr_extents + * initialization. + */ + map_to->forward = forward; + map_to->reverse = reverse; + map_to->nr_extents = nr_extents; + return 0; +} + +static void free_mnt_idmap(struct mnt_idmap *idmap) +{ + if (idmap->uid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) { + kfree(idmap->uid_map.forward); + kfree(idmap->uid_map.reverse); + } + if (idmap->gid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) { + kfree(idmap->gid_map.forward); + kfree(idmap->gid_map.reverse); + } + kfree(idmap); +} + struct mnt_idmap *alloc_mnt_idmap(struct user_namespace *mnt_userns) { struct mnt_idmap *idmap; + int ret; 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); + ret = copy_mnt_idmap(&mnt_userns->uid_map, &idmap->uid_map); + if (!ret) + ret = copy_mnt_idmap(&mnt_userns->gid_map, &idmap->gid_map); + if (ret) { + free_mnt_idmap(idmap); + idmap = ERR_PTR(ret); + } return idmap; } @@ -234,9 +312,7 @@ 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)) { - put_user_ns(idmap->owner); - kfree(idmap); - } + if (idmap != &nop_mnt_idmap && refcount_dec_and_test(&idmap->count)) + free_mnt_idmap(idmap); } EXPORT_SYMBOL_GPL(mnt_idmap_put); diff --git a/include/linux/uidgid.h b/include/linux/uidgid.h index b0542cd11aeb..415a7ca2b882 100644 --- a/include/linux/uidgid.h +++ b/include/linux/uidgid.h @@ -17,6 +17,7 @@ struct user_namespace; extern struct user_namespace init_user_ns; +struct uid_gid_map; typedef struct { uid_t val; @@ -138,6 +139,9 @@ static inline bool kgid_has_mapping(struct user_namespace *ns, kgid_t gid) return from_kgid(ns, gid) != (gid_t) -1; } +u32 map_id_down(struct uid_gid_map *map, u32 id); +u32 map_id_up(struct uid_gid_map *map, u32 id); + #else static inline kuid_t make_kuid(struct user_namespace *from, uid_t uid) @@ -186,6 +190,15 @@ static inline bool kgid_has_mapping(struct user_namespace *ns, kgid_t gid) return gid_valid(gid); } +static inline u32 map_id_down(struct uid_gid_map *map, u32 id) +{ + return id; +} + +static inline u32 map_id_up(struct uid_gid_map *map, u32 id) +{ + return id; +} #endif /* CONFIG_USER_NS */ #endif /* _LINUX_UIDGID_H */ diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 625101249e4d..ce4d99df5f0e 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -332,7 +332,7 @@ static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count) return id; } -static u32 map_id_down(struct uid_gid_map *map, u32 id) +u32 map_id_down(struct uid_gid_map *map, u32 id) { return map_id_range_down(map, id, 1); } @@ -375,7 +375,7 @@ map_id_up_max(unsigned extents, struct uid_gid_map *map, u32 id) sizeof(struct uid_gid_extent), cmp_map_id); } -static u32 map_id_up(struct uid_gid_map *map, u32 id) +u32 map_id_up(struct uid_gid_map *map, u32 id) { struct uid_gid_extent *extent; unsigned extents = map->nr_extents; |