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Date: Fri, 24 Apr 2015 13:04:16 +0200
From: Andreas Gruenbacher <andreas.gruenbacher@...il.com>
To: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-nfs@...r.kernel.org
Subject: [RFC v3 19/45] richacl: Also recognize nontrivial mode-equivalent acls
So far, richacl_equiv_mode() is relatively limited in the types of acl it
considers equivalent to a file mode: it only accepts masked acls with a single
everyone@:rwpxd::allow entry.
Change this to consider all acls equivalent to file modes if they only consist
of owner@, group@, and everyone@ entries and the owner@ permissions do not
depend on whether the owner is a member in the owning group.
Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
---
fs/richacl_base.c | 150 ++++++++++++++++++++++++++++++++++++++----------
include/linux/richacl.h | 1 +
2 files changed, 122 insertions(+), 29 deletions(-)
diff --git a/fs/richacl_base.c b/fs/richacl_base.c
index db27542..54cb482 100644
--- a/fs/richacl_base.c
+++ b/fs/richacl_base.c
@@ -439,49 +439,141 @@ richacl_inherit(const struct richacl *dir_acl, int isdir)
}
/**
- * richacl_equiv_mode - check if @acl is equivalent to file permission bits
- * @mode_p: the file mode (including the file type)
+ * __richacl_equiv_mode - compute the mode equivalent of @acl
*
- * If @acl can be fully represented by file permission bits, this function
- * returns 0, and the file permission bits in @mode_p are set to the equivalent
- * of @acl.
+ * This function does not consider the masks in @acl.
*
- * This function is used to avoid storing richacls on disk if the acl can be
- * computed from the file permission bits. It allows user-space to make sure
- * that a file has no explicit richacl set.
+ * An acl is considered equivalent to a file mode if it only consists of
+ * owner@, group@, and everyone@ entries and the owner@ permissions do not
+ * depend on whether the owner is a member in the owning group.
*/
int
-richacl_equiv_mode(const struct richacl *acl, mode_t *mode_p)
+__richacl_equiv_mode(const struct richacl *acl, mode_t *mode_p)
{
- const struct richace *ace = acl->a_entries;
- unsigned int x;
- mode_t mask;
-
- if (acl->a_count != 1 ||
- acl->a_flags != RICHACL_MASKED ||
- !richace_is_everyone(ace) ||
- !richace_is_allow(ace) ||
- ace->e_flags & ~RICHACE_SPECIAL_WHO)
+ mode_t mode = *mode_p;
+
+ /*
+ * The RICHACE_DELETE_CHILD flag is meaningless for non-directories, so
+ * we ignore it.
+ */
+ unsigned int x = S_ISDIR(mode) ? 0 : RICHACE_DELETE_CHILD;
+ struct {
+ unsigned int allowed;
+ unsigned int defined; /* allowed or denied */
+ } owner = {
+ .allowed = RICHACE_POSIX_ALWAYS_ALLOWED,
+ .defined = RICHACE_POSIX_ALWAYS_ALLOWED | RICHACE_POSIX_OWNER_ALLOWED | x,
+ }, group = {
+ .allowed = RICHACE_POSIX_ALWAYS_ALLOWED,
+ .defined = RICHACE_POSIX_ALWAYS_ALLOWED | x,
+ }, everyone = {
+ .allowed = RICHACE_POSIX_ALWAYS_ALLOWED,
+ .defined = RICHACE_POSIX_ALWAYS_ALLOWED | x,
+ };
+ const struct richace *ace;
+
+ richacl_for_each_entry(ace, acl) {
+ if (ace->e_flags & ~RICHACE_SPECIAL_WHO)
+ return -1;
+
+ if (richace_is_owner(ace) || richace_is_everyone(ace)) {
+ x = ace->e_mask & ~owner.defined;
+ if (richace_is_allow(ace)) {
+ unsigned int group_denied = group.defined & ~group.allowed;
+
+ if (x & group_denied)
+ return -1;
+ owner.allowed |= x;
+ } else /* if (richace_is_deny(ace)) */ {
+ if (x & group.allowed)
+ return -1;
+ }
+ owner.defined |= x;
+
+ if (richace_is_everyone(ace)) {
+ x = ace->e_mask;
+ if (richace_is_allow(ace)) {
+ group.allowed |= x & ~group.defined;
+ everyone.allowed |= x & ~everyone.defined;
+ }
+ group.defined |= x;
+ everyone.defined |= x;
+ }
+ } else if (richace_is_group(ace)) {
+ x = ace->e_mask & ~group.defined;
+ if (richace_is_allow(ace))
+ group.allowed |= x;
+ group.defined |= x;
+ } else
+ return -1;
+ }
+
+ if (group.allowed & ~owner.defined)
return -1;
- /* Mask flags we can ignore */
- x = ~RICHACE_POSIX_ALWAYS_ALLOWED;
- if (!S_ISDIR(*mode_p))
- x &= ~RICHACE_DELETE_CHILD;
+ if (acl->a_flags & RICHACL_MASKED) {
+ owner.allowed &= acl->a_owner_mask;
+ group.allowed &= acl->a_group_mask;
+ everyone.allowed &= acl->a_other_mask;
+ }
- mask = richacl_masks_to_mode(acl);
- if (((acl->a_group_mask ^ richacl_mode_to_mask(mask >> 3)) & x) ||
- ((acl->a_other_mask ^ richacl_mode_to_mask(mask)) & x))
+ mode = (mode & ~S_IRWXUGO) |
+ (richacl_mask_to_mode(owner.allowed) << 6) |
+ (richacl_mask_to_mode(group.allowed) << 3) |
+ richacl_mask_to_mode(everyone.allowed);
+
+ /* Mask flags we can ignore */
+ x = ~(S_ISDIR(mode) ? 0 : RICHACE_DELETE_CHILD);
+ if (((richacl_mode_to_mask(mode >> 6) ^ owner.allowed) & x) ||
+ ((richacl_mode_to_mask(mode >> 3) ^ group.allowed) & x) ||
+ ((richacl_mode_to_mask(mode) ^ everyone.allowed) & x))
return -1;
- x &= ~RICHACE_POSIX_OWNER_ALLOWED;
- if ((acl->a_owner_mask ^ richacl_mode_to_mask(mask >> 6)) & x)
+ *mode_p = mode;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(__richacl_equiv_mode);
+
+/**
+ * richacl_equiv_mode - determine if @acl is equivalent to a file mode
+ * @mode_p: the file mode
+ *
+ * The file type in @mode_p must be set when calling richacl_equiv_mode().
+ *
+ * Returns with 0 if @acl is equivalent to a file mode; in that case, the
+ * file permission bits in @mode_p are set to the mode equivalent of @acl.
+ */
+int
+richacl_equiv_mode(const struct richacl *acl, mode_t *mode_p)
+{
+ mode_t mode = *mode_p;
+
+ if (acl->a_flags & ~RICHACL_MASKED)
return -1;
- if ((ace->e_mask ^ RICHACE_POSIX_MODE_ALL) & x)
+ if (__richacl_equiv_mode(acl, &mode))
return -1;
- *mode_p = (*mode_p & ~S_IRWXUGO) | mask;
+ if (acl->a_flags & RICHACL_MASKED) {
+ mode_t mask = richacl_masks_to_mode(acl);
+ unsigned int x;
+
+ /* Mask flags we can ignore */
+ x = ~(RICHACE_POSIX_ALWAYS_ALLOWED |
+ (S_ISDIR(mode) ? 0 : RICHACE_DELETE_CHILD));
+
+ if (((acl->a_group_mask ^ richacl_mode_to_mask(mask >> 3)) & x) ||
+ ((acl->a_other_mask ^ richacl_mode_to_mask(mask)) & x))
+ return -1;
+
+ x &= ~RICHACE_POSIX_OWNER_ALLOWED;
+ if ((acl->a_owner_mask ^ richacl_mode_to_mask(mask >> 6)) & x)
+ return -1;
+
+ mode &= ~S_IRWXUGO | mask;
+ }
+
+ *mode_p = mode;
return 0;
}
EXPORT_SYMBOL_GPL(richacl_equiv_mode);
diff --git a/include/linux/richacl.h b/include/linux/richacl.h
index c6fd0a1..8a92b89 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -297,6 +297,7 @@ extern unsigned int richacl_want_to_mask(unsigned int);
extern void richacl_compute_max_masks(struct richacl *);
extern struct richacl *richacl_chmod(struct richacl *, mode_t);
extern struct richacl *richacl_inherit(const struct richacl *, int);
+extern int __richacl_equiv_mode(const struct richacl *, mode_t *);
extern int richacl_equiv_mode(const struct richacl *, mode_t *);
/* richacl_inode.c */
--
2.1.0
--
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