[RFC v7 33/41] richacl: Add support for unmapped identifiers

From: Andreas Gruenbacher
Date: Sat Sep 05 2015 - 06:33:39 EST

Some remote file systems like nfs may return user or group identifiers
that cannot be mapped to local uids / gids. Allow to represent such
unmapped identifiers in richacls. (We still cannot represent unmapped
owners and owning groups, however.)

In the in-memory representation, the richacl is followed by a list of
NUL-terminated strings, with no padding. Entries with an unmapped
identifier have the RICHACE_UNMAPPED_WHO flag set, and ace->e_id.offs
specifies the offset into this list. Multiple entries can refer to the
same offset.

The xattr representation is similar, but ace->e_id is ignored, and the
list of unmapped identifier strings contains a string for each acl entry
whose RICHACE_UNMAPPED_WHO flag is set.

Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
---
fs/richacl_base.c | 139 ++++++++++++++++++++++++++++++++++++++++++++----
fs/richacl_compat.c | 18 +++----
fs/richacl_inode.c | 4 +-
fs/richacl_xattr.c | 69 ++++++++++++++++++++----
include/linux/richacl.h | 33 ++++++++++--
5 files changed, 227 insertions(+), 36 deletions(-)

diff --git a/fs/richacl_base.c b/fs/richacl_base.c
index a85b7a3..281e396 100644
--- a/fs/richacl_base.c
+++ b/fs/richacl_base.c
@@ -23,22 +23,25 @@
MODULE_LICENSE("GPL");

/**
- * richacl_alloc - allocate a richacl
+ * __richacl_alloc - allocate a richacl
* @count: number of entries
+ * @unmapped_size: size to reserve for unmapped identifiers
*/
struct richacl *
-richacl_alloc(int count, gfp_t gfp)
+__richacl_alloc(unsigned int count, size_t unmapped_size, gfp_t gfp)
{
- size_t size = sizeof(struct richacl) + count * sizeof(struct richace);
+ size_t size = sizeof(struct richacl) + count * sizeof(struct richace) +
+ unmapped_size;
struct richacl *acl = kzalloc(size, gfp);

if (acl) {
atomic_set(&acl->a_base.ba_refcount, 1);
acl->a_count = count;
+ acl->a_unmapped_size = unmapped_size;
}
return acl;
}
-EXPORT_SYMBOL_GPL(richacl_alloc);
+EXPORT_SYMBOL_GPL(__richacl_alloc);

/**
* richacl_clone - create a copy of a richacl
@@ -47,7 +50,8 @@ struct richacl *
richacl_clone(const struct richacl *acl, gfp_t gfp)
{
int count = acl->a_count;
- size_t size = sizeof(struct richacl) + count * sizeof(struct richace);
+ size_t size = sizeof(struct richacl) + count * sizeof(struct richace) +
+ acl->a_unmapped_size;
struct richacl *dup = kmalloc(size, gfp);

if (dup) {
@@ -59,6 +63,9 @@ richacl_clone(const struct richacl *acl, gfp_t gfp)

/**
* richace_copy - copy an acl entry
+ *
+ * If @from has an unmapped who value (from->e_flags & RICHACE_UNMAPPED_WHO),
+ * it can only be copied within the same acl!
*/
void
richace_copy(struct richace *to, const struct richace *from)
@@ -66,6 +73,82 @@ richace_copy(struct richace *to, const struct richace *from)
memcpy(to, from, sizeof(struct richace));
}

+/**
+ * richacl_add_unmapped_identifier
+ * @pacl: Pointer to an acl
+ * @pace: acl entry within @acl
+ * @who: unmapped identifier
+ * @len: length of @who
+ * @gfp: memory allocation flags
+ *
+ * Add an unmapped identifier to an acl, possibly reallocating the acl.
+ */
+int richacl_add_unmapped_identifier(struct richacl **pacl,
+ struct richace **pace,
+ const char *who,
+ unsigned int len, gfp_t gfp)
+{
+ struct richacl *acl = *pacl;
+ size_t size = sizeof(struct richacl) +
+ acl->a_count * sizeof(struct richace) +
+ acl->a_unmapped_size + len + 1;
+ unsigned int index = *pace - acl->a_entries;
+
+ acl = krealloc(*pacl, size, gfp);
+ if (acl) {
+ char *unmapped = (char *)(acl->a_entries + acl->a_count);
+ struct richace *ace = acl->a_entries + index;
+
+ ace->e_flags |= RICHACE_UNMAPPED_WHO;
+ ace->e_flags &= ~RICHACE_SPECIAL_WHO;
+ ace->e_id.offs = acl->a_unmapped_size;
+ memcpy(unmapped + ace->e_id.offs, who, len);
+ unmapped[ace->e_id.offs + len] = 0;
+ acl->a_unmapped_size += len + 1;
+ *pace = ace;
+ *pacl = acl;
+ return 0;
+ }
+ return -1;
+}
+EXPORT_SYMBOL_GPL(richacl_add_unmapped_identifier);
+
+/**
+ * richace_unmapped_identifier - get unmapped identifier
+ * @acl: acl containing @ace
+ * @ace: acl entry
+ *
+ * Get the unmapped identifier of @ace as a NUL-terminated string, or NULL if
+ * @ace doesn't have an unmapped identifier.
+ */
+const char *richace_unmapped_identifier(const struct richace *ace,
+ const struct richacl *acl)
+{
+ const char *unmapped = (char *)(acl->a_entries + acl->a_count);
+
+ if (!(ace->e_flags & RICHACE_UNMAPPED_WHO))
+ return NULL;
+ return unmapped + ace->e_id.offs;
+}
+EXPORT_SYMBOL(richace_unmapped_identifier);
+
+/**
+ * richacl_has_unmapped_identifiers
+ *
+ * Check if an acl has unmapped identifiers.
+ */
+bool richacl_has_unmapped_identifiers(struct richacl *acl)
+{
+ struct richace *ace;
+
+ richacl_for_each_entry(ace, acl) {
+ if (ace->e_flags & RICHACE_UNMAPPED_WHO)
+ return true;
+ }
+ return false;
+}
+EXPORT_SYMBOL_GPL(richacl_has_unmapped_identifiers);
+
/*
* richacl_mask_to_mode - compute the file permission bits from mask
* @mask: %RICHACE_* permission mask
@@ -213,7 +296,7 @@ static unsigned int richacl_allowed_to_who(struct richacl *acl,
richacl_for_each_entry_reverse(ace, acl) {
if (richace_is_inherit_only(ace))
continue;
- if (richace_is_same_identifier(ace, who) ||
+ if (richace_is_same_identifier(acl, ace, who) ||
richace_is_everyone(ace)) {
if (richace_is_allow(ace))
allowed |= ace->e_mask;
@@ -502,46 +585,73 @@ richacl_inherit(const struct richacl *dir_acl, int isdir)
const struct richace *dir_ace;
struct richacl *acl = NULL;
struct richace *ace;
- int count = 0;
+ unsigned int count = 0, unmapped_size = 0, offset = 0;
+ const char *dir_unmapped;
+ char *unmapped;

if (isdir) {
richacl_for_each_entry(dir_ace, dir_acl) {
if (!richace_is_inheritable(dir_ace))
continue;
+
count++;
+ dir_unmapped =
+ richace_unmapped_identifier(dir_ace, dir_acl);
+ if (dir_unmapped)
+ unmapped_size += strlen(dir_unmapped) + 1;
}
if (!count)
return NULL;
- acl = richacl_alloc(count, GFP_KERNEL);
+ acl = __richacl_alloc(count, unmapped_size, GFP_KERNEL);
if (!acl)
return ERR_PTR(-ENOMEM);
ace = acl->a_entries;
+ unmapped = (char *)(acl->a_entries + acl->a_count);
richacl_for_each_entry(dir_ace, dir_acl) {
if (!richace_is_inheritable(dir_ace))
continue;
+
richace_copy(ace, dir_ace);
if (dir_ace->e_flags & RICHACE_NO_PROPAGATE_INHERIT_ACE)
ace->e_flags &= ~RICHACE_INHERITANCE_FLAGS;
else if ((dir_ace->e_flags & RICHACE_FILE_INHERIT_ACE) &&
!(dir_ace->e_flags & RICHACE_DIRECTORY_INHERIT_ACE))
ace->e_flags |= RICHACE_INHERIT_ONLY_ACE;
+
+ dir_unmapped =
+ richace_unmapped_identifier(dir_ace, dir_acl);
+ if (dir_unmapped) {
+ size_t sz = strlen(dir_unmapped) + 1;
+
+ ace->e_id.offs = offset;
+ memcpy(unmapped, dir_unmapped, sz);
+ unmapped += sz;
+ offset += sz;
+ }
ace++;
}
} else {
richacl_for_each_entry(dir_ace, dir_acl) {
if (!(dir_ace->e_flags & RICHACE_FILE_INHERIT_ACE))
continue;
+
count++;
+ dir_unmapped =
+ richace_unmapped_identifier(dir_ace, dir_acl);
+ if (dir_unmapped)
+ unmapped_size += strlen(dir_unmapped) + 1;
}
if (!count)
return NULL;
- acl = richacl_alloc(count, GFP_KERNEL);
+ acl = __richacl_alloc(count, unmapped_size, GFP_KERNEL);
if (!acl)
return ERR_PTR(-ENOMEM);
ace = acl->a_entries;
+ unmapped = (char *)(acl->a_entries + acl->a_count);
richacl_for_each_entry(dir_ace, dir_acl) {
if (!(dir_ace->e_flags & RICHACE_FILE_INHERIT_ACE))
continue;
+
richace_copy(ace, dir_ace);
ace->e_flags &= ~RICHACE_INHERITANCE_FLAGS;
/*
@@ -549,6 +659,17 @@ richacl_inherit(const struct richacl *dir_acl, int isdir)
* non-directories, so clear it.
*/
ace->e_mask &= ~RICHACE_DELETE_CHILD;
+
+ dir_unmapped =
+ richace_unmapped_identifier(dir_ace, dir_acl);
+ if (dir_unmapped) {
+ size_t sz = strlen(dir_unmapped) + 1;
+
+ ace->e_id.offs = offset;
+ memcpy(unmapped, dir_unmapped, sz);
+ unmapped += sz;
+ offset += sz;
+ }
ace++;
}
}
diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c
index 632409f..8aeafa8 100644
--- a/fs/richacl_compat.c
+++ b/fs/richacl_compat.c
@@ -71,11 +71,13 @@ richacl_insert_entry(struct richacl_alloc *alloc, struct richace **ace)
{
struct richacl *acl = alloc->acl;
unsigned int index = *ace - acl->a_entries;
- size_t tail_size = (acl->a_count - index) * sizeof(struct richace);
+ size_t tail_size = (acl->a_count - index) * sizeof(struct richace) +
+ acl->a_unmapped_size;

if (alloc->count == acl->a_count) {
size_t new_size = sizeof(struct richacl) +
- (acl->a_count + 1) * sizeof(struct richace);
+ (acl->a_count + 1) * sizeof(struct richace) +
+ acl->a_unmapped_size;

acl = krealloc(acl, new_size, GFP_KERNEL);
if (!acl)
@@ -103,10 +105,6 @@ struct richace *richacl_append_entry(struct richacl_alloc *alloc)
struct richacl *acl = alloc->acl;
struct richace *ace = acl->a_entries + acl->a_count;

- if (alloc->count > alloc->acl->a_count) {
- acl->a_count++;
- return ace;
- }
return richacl_insert_entry(alloc, &ace) ? NULL : ace;
}
EXPORT_SYMBOL_GPL(richacl_append_entry);
@@ -261,12 +259,12 @@ __richacl_propagate_everyone(struct richacl_alloc *alloc, struct richace *who,
if (richace_is_inherit_only(ace))
continue;
if (richace_is_allow(ace)) {
- if (richace_is_same_identifier(ace, who)) {
+ if (richace_is_same_identifier(acl, ace, who)) {
allow &= ~ace->e_mask;
allow_last = ace;
}
} else if (richace_is_deny(ace)) {
- if (richace_is_same_identifier(ace, who))
+ if (richace_is_same_identifier(acl, ace, who))
allow &= ~ace->e_mask;
else if (allow & ace->e_mask)
allow_last = NULL;
@@ -608,7 +606,7 @@ __richacl_isolate_who(struct richacl_alloc *alloc, struct richace *who,
richacl_for_each_entry(ace, acl) {
if (richace_is_inherit_only(ace))
continue;
- if (richace_is_same_identifier(ace, who) &&
+ if (richace_is_same_identifier(acl, ace, who) &&
richace_is_deny(ace))
deny &= ~ace->e_mask;
}
@@ -625,7 +623,7 @@ __richacl_isolate_who(struct richacl_alloc *alloc, struct richace *who,
if (richace_is_inherit_only(ace))
continue;
if (richace_is_deny(ace)) {
- if (richace_is_same_identifier(ace, who))
+ if (richace_is_same_identifier(acl, ace, who))
break;
} else if (richace_is_allow(ace) &&
(ace->e_mask & deny)) {
diff --git a/fs/richacl_inode.c b/fs/richacl_inode.c
index df175c1..ff8b192 100644
--- a/fs/richacl_inode.c
+++ b/fs/richacl_inode.c
@@ -159,8 +159,10 @@ richacl_permission(struct inode *inode, const struct richacl *acl,
} else if (richace_is_unix_group(ace)) {
if (!in_group_p(ace->e_id.gid))
continue;
- } else
+ } else if (richace_is_everyone(ace))
goto entry_matches_everyone;
+ else
+ continue;

/*
* Apply the group file mask to entries other than owner@ and
diff --git a/fs/richacl_xattr.c b/fs/richacl_xattr.c
index cd9979d..e9622f6 100644
--- a/fs/richacl_xattr.c
+++ b/fs/richacl_xattr.c
@@ -33,7 +33,8 @@ richacl_from_xattr(struct user_namespace *user_ns,
const struct richace_xattr *xattr_ace = (void *)(xattr_acl + 1);
struct richacl *acl;
struct richace *ace;
- int count;
+ unsigned int count, offset;
+ char *unmapped;

if (size < sizeof(*xattr_acl) ||
xattr_acl->a_version != RICHACL_XATTR_VERSION ||
@@ -43,10 +44,11 @@ richacl_from_xattr(struct user_namespace *user_ns,
count = le16_to_cpu(xattr_acl->a_count);
if (count > RICHACL_XATTR_MAX_COUNT)
return ERR_PTR(-EINVAL);
- if (size != count * sizeof(*xattr_ace))
+ if (size < count * sizeof(*xattr_ace))
return ERR_PTR(-EINVAL);
+ size -= count * sizeof(*xattr_ace);

- acl = richacl_alloc(count, GFP_NOFS);
+ acl = __richacl_alloc(count, size, GFP_NOFS);
if (!acl)
return ERR_PTR(-ENOMEM);

@@ -61,6 +63,16 @@ richacl_from_xattr(struct user_namespace *user_ns,
if (acl->a_other_mask & ~RICHACE_VALID_MASK)
goto fail_einval;

+ unmapped = (char *)(acl->a_entries + count);
+ if (size) {
+ char *xattr_unmapped = (char *)(xattr_ace + count);
+
+ if (xattr_unmapped[size - 1] != 0)
+ goto fail_einval;
+ memcpy(unmapped, xattr_unmapped, size);
+ }
+ offset = 0;
+
richacl_for_each_entry(ace, acl) {
ace->e_type = le16_to_cpu(xattr_ace->e_type);
ace->e_flags = le16_to_cpu(xattr_ace->e_flags);
@@ -72,6 +84,15 @@ richacl_from_xattr(struct user_namespace *user_ns,
ace->e_id.special = le32_to_cpu(xattr_ace->e_id);
if (ace->e_id.special > RICHACE_EVERYONE_SPECIAL_ID)
goto fail_einval;
+ } else if (ace->e_flags & RICHACE_UNMAPPED_WHO) {
+ size_t sz;
+
+ if (offset == size)
+ goto fail_einval;
+ ace->e_id.offs = offset;
+ sz = strlen(unmapped) + 1;
+ unmapped += sz;
+ offset += sz;
} else if (ace->e_flags & RICHACE_IDENTIFIER_GROUP) {
u32 id = le32_to_cpu(xattr_ace->e_id);

@@ -88,10 +109,12 @@ richacl_from_xattr(struct user_namespace *user_ns,
if (ace->e_type > RICHACE_ACCESS_DENIED_ACE_TYPE ||
(ace->e_mask & ~RICHACE_VALID_MASK))
goto fail_einval;
-
xattr_ace++;
}

+ if (offset != size)
+ goto fail_einval;
+
return acl;

fail_einval:
@@ -107,8 +130,15 @@ size_t
richacl_xattr_size(const struct richacl *acl)
{
size_t size = sizeof(struct richacl_xattr);
+ const struct richace *ace;

size += sizeof(struct richace_xattr) * acl->a_count;
+ richacl_for_each_entry(ace, acl) {
+ const char *unmapped = richace_unmapped_identifier(ace, acl);
+
+ if (unmapped)
+ size += strlen(unmapped) + 1;
+ }
return size;
}
EXPORT_SYMBOL_GPL(richacl_xattr_size);
@@ -127,6 +157,7 @@ richacl_to_xattr(struct user_namespace *user_ns,
struct richace_xattr *xattr_ace;
const struct richace *ace;
size_t real_size;
+ char *xattr_unmapped;

real_size = richacl_xattr_size(acl);
if (!buffer)
@@ -143,18 +174,33 @@ richacl_to_xattr(struct user_namespace *user_ns,
xattr_acl->a_other_mask = cpu_to_le32(acl->a_other_mask);

xattr_ace = (void *)(xattr_acl + 1);
+ xattr_unmapped = (char *)(xattr_ace + acl->a_count);
richacl_for_each_entry(ace, acl) {
+ const char *who;
+
xattr_ace->e_type = cpu_to_le16(ace->e_type);
xattr_ace->e_flags = cpu_to_le16(ace->e_flags);
xattr_ace->e_mask = cpu_to_le32(ace->e_mask);
if (ace->e_flags & RICHACE_SPECIAL_WHO)
xattr_ace->e_id = cpu_to_le32(ace->e_id.special);
- else if (ace->e_flags & RICHACE_IDENTIFIER_GROUP)
- xattr_ace->e_id =
- cpu_to_le32(from_kgid(user_ns, ace->e_id.gid));
- else
- xattr_ace->e_id =
- cpu_to_le32(from_kuid(user_ns, ace->e_id.uid));
+ else {
+ who = richace_unmapped_identifier(ace, acl);
+ if (who) {
+ size_t sz = strlen(who) + 1;
+
+ xattr_ace->e_id = 0;
+ memcpy(xattr_unmapped, who, sz);
+ xattr_unmapped += sz;
+ } else if (ace->e_flags & RICHACE_IDENTIFIER_GROUP) {
+ u32 id = from_kgid(user_ns, ace->e_id.gid);
+
+ xattr_ace->e_id = cpu_to_le32(id);
+ } else {
+ u32 id = from_kuid(user_ns, ace->e_id.uid);
+
+ xattr_ace->e_id = cpu_to_le32(id);
+ }
+ }
xattr_ace++;
}
return real_size;
@@ -184,7 +230,8 @@ static void richacl_fix_xattr_userns(
return;
count = size / sizeof(*xattr_ace);
for (; count; count--, xattr_ace++) {
- if (xattr_ace->e_flags & cpu_to_le16(RICHACE_SPECIAL_WHO))
+ if (xattr_ace->e_flags & cpu_to_le16(RICHACE_SPECIAL_WHO |
+ RICHACE_UNMAPPED_WHO))
continue;
if (xattr_ace->e_flags &
cpu_to_le16(RICHACE_IDENTIFIER_GROUP)) {
diff --git a/include/linux/richacl.h b/include/linux/richacl.h
index f48c04e..1822666 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -29,6 +29,7 @@ struct richace {
kuid_t uid;
kgid_t gid;
unsigned int special;
+ unsigned short offs; /* unmapped offset */
} e_id;
};

@@ -39,6 +40,7 @@ struct richacl {
unsigned int a_other_mask;
unsigned short a_count;
unsigned short a_flags;
+ unsigned short a_unmapped_size;
struct richace a_entries[0];
};

@@ -77,6 +79,7 @@ struct richacl {
#define RICHACE_INHERIT_ONLY_ACE 0x0008
#define RICHACE_IDENTIFIER_GROUP 0x0040
#define RICHACE_INHERITED_ACE 0x0080
+#define RICHACE_UNMAPPED_WHO 0x2000
#define RICHACE_SPECIAL_WHO 0x4000

#define RICHACE_VALID_FLAGS ( \
@@ -86,6 +89,7 @@ struct richacl {
RICHACE_INHERIT_ONLY_ACE | \
RICHACE_IDENTIFIER_GROUP | \
RICHACE_INHERITED_ACE | \
+ RICHACE_UNMAPPED_WHO | \
RICHACE_SPECIAL_WHO)

#define RICHACE_INHERITANCE_FLAGS ( \
@@ -310,14 +314,28 @@ richace_is_deny(const struct richace *ace)
* richace_is_same_identifier - are both identifiers the same?
*/
static inline bool
-richace_is_same_identifier(const struct richace *a, const struct richace *b)
+richace_is_same_identifier(const struct richacl *acl,
+ const struct richace *ace1,
+ const struct richace *ace2)
{
- return !((a->e_flags ^ b->e_flags) &
- (RICHACE_SPECIAL_WHO | RICHACE_IDENTIFIER_GROUP)) &&
- !memcmp(&a->e_id, &b->e_id, sizeof(a->e_id));
+ const char *unmapped = (char *)(acl->a_entries + acl->a_count);
+
+ return !((ace1->e_flags ^ ace2->e_flags) &
+ (RICHACE_SPECIAL_WHO |
+ RICHACE_IDENTIFIER_GROUP |
+ RICHACE_UNMAPPED_WHO)) &&
+ ((ace1->e_flags & RICHACE_UNMAPPED_WHO) ?
+ !strcmp(unmapped + ace1->e_id.offs,
+ unmapped + ace2->e_id.offs) :
+ !memcmp(&ace1->e_id, &ace2->e_id, sizeof(ace1->e_id)));
+}
+
+extern struct richacl *__richacl_alloc(unsigned int, size_t, gfp_t);
+static inline struct richacl *richacl_alloc(unsigned int count, gfp_t gfp)
+{
+ return __richacl_alloc(count, 0, gfp);
}

-extern struct richacl *richacl_alloc(int, gfp_t);
extern struct richacl *richacl_clone(const struct richacl *, gfp_t);
extern void richace_copy(struct richace *, const struct richace *);
extern int richacl_masks_to_mode(const struct richacl *);
@@ -327,6 +345,11 @@ extern void richacl_compute_max_masks(struct richacl *);
extern struct richacl *richacl_chmod(struct richacl *, mode_t);
extern int richacl_equiv_mode(const struct richacl *, mode_t *);
extern struct richacl *richacl_inherit(const struct richacl *, int);
+extern int richacl_add_unmapped_identifier(struct richacl **, struct richace **,
+ const char *, unsigned int, gfp_t);
+extern const char *richace_unmapped_identifier(const struct richace *,
+ const struct richacl *);
+extern bool richacl_has_unmapped_identifiers(struct richacl *);

/* richacl_inode.c */
extern int richacl_permission(struct inode *, const struct richacl *, int);
--
2.4.3

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