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mnt_idmapping: remove nop check

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All mounts default to nop_mnt_idmap and we don't allow creating idmapped
mounts that reuse the idmapping of the filesystem. So unless someone
passes a non-superblock namespace to these helpers this check will
always be false. Remove it and replace it with a simple check for
nop_mnt_idmap.

Link: https://lore.kernel.org/r/20231122-vfs-mnt_idmap-v1-2-dae4abdde5bd@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2023-11-22 13:44:38 +01:00
parent e65a29f023
commit 90fbd8b175
1 changed files with 8 additions and 28 deletions
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36
fs/mnt_idmapping.c
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@ -39,26 +39,6 @@ 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
@ -68,8 +48,8 @@ static inline bool no_idmapping(const struct user_namespace *mnt_userns,
* 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() 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()
@ -87,7 +67,7 @@ vfsuid_t make_vfsuid(struct mnt_idmap *idmap,
uid_t uid;
struct user_namespace *mnt_userns = idmap->owner;
if (no_idmapping(mnt_userns, fs_userns))
if (idmap == &nop_mnt_idmap)
return VFSUIDT_INIT(kuid);
if (initial_idmapping(fs_userns))
uid = __kuid_val(kuid);
@ -108,8 +88,8 @@ EXPORT_SYMBOL_GPL(make_vfsuid);
* 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() 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()
@ -125,7 +105,7 @@ vfsgid_t make_vfsgid(struct mnt_idmap *idmap,
gid_t gid;
struct user_namespace *mnt_userns = idmap->owner;
if (no_idmapping(mnt_userns, fs_userns))
if (idmap == &nop_mnt_idmap)
return VFSGIDT_INIT(kgid);
if (initial_idmapping(fs_userns))
gid = __kgid_val(kgid);
@ -154,7 +134,7 @@ kuid_t from_vfsuid(struct mnt_idmap *idmap,
uid_t uid;
struct user_namespace *mnt_userns = idmap->owner;
if (no_idmapping(mnt_userns, fs_userns))
if (idmap == &nop_mnt_idmap)
return AS_KUIDT(vfsuid);
uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid));
if (uid == (uid_t)-1)
@ -182,7 +162,7 @@ kgid_t from_vfsgid(struct mnt_idmap *idmap,
gid_t gid;
struct user_namespace *mnt_userns = idmap->owner;
if (no_idmapping(mnt_userns, fs_userns))
if (idmap == &nop_mnt_idmap)
return AS_KGIDT(vfsgid);
gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid));
if (gid == (gid_t)-1)