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fs/mnt_idmapping: introduce an invalid_mnt_idmap

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Link: https://lore.kernel.org/linux-fsdevel/20240904-baugrube-erhoben-b3c1c49a2645@brauner/
Suggested-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Alexander Mikhalitsyn 2024-09-06 16:34:52 +02:00 committed by Miklos Szeredi
parent 0c6793823d
commit ffcdc4c628
2 changed files with 21 additions and 2 deletions
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22
fs/mnt_idmapping.c
View File

@ -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);

1
include/linux/mnt_idmapping.h
View File

@ -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 {