From: "Aneesh Kumar K.V" Subject: [PATCH -V5 18/24] richacl: Check if an acl is equivalent to a file mode Date: Wed, 23 Feb 2011 19:22:05 +0530 Message-ID: <1298469131-16555-19-git-send-email-aneesh.kumar@linux.vnet.ibm.com> References: <1298469131-16555-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Cc: aneesh.kumar@linux.vnet.ibm.com, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Andreas Gruenbacher To: sfrench@us.ibm.com, agruen@linbit.com, dilger.kernel@dilger.ca, sandeen@redhat.com, tytso@mit.edu, bfields@fieldses.org, jlayton@redhat.com Return-path: In-Reply-To: <1298469131-16555-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org From: Andreas Gruenbacher This function is used to avoid storing richacls on disk if the acl can be computed from the file permission bits. Signed-off-by: Andreas Gruenbacher Signed-off-by: Aneesh Kumar K.V --- fs/richacl_base.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/richacl.h | 1 + 2 files changed, 55 insertions(+), 0 deletions(-) diff --git a/fs/richacl_base.c b/fs/richacl_base.c index 5e926ad..e60440b 100644 --- a/fs/richacl_base.c +++ b/fs/richacl_base.c @@ -561,3 +561,57 @@ richacl_inherit(const struct richacl *dir_acl, int isdir) return acl; } + +/** + * richacl_equiv_mode - check if @acl is equivalent to file permission bits + * @mode_p: the file mode (including the file type) + * + * 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 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. + */ +int +richacl_equiv_mode(const struct richacl *acl, mode_t *mode_p) +{ + const struct richace *ace = acl->a_entries; + unsigned int x; + mode_t mode; + + if (acl->a_count != 1 || + acl->a_flags != ACL4_MASKED || + !richace_is_everyone(ace) || + !richace_is_allow(ace) || + ace->e_flags & ~ACE4_SPECIAL_WHO) + return -1; + + /* + * Figure out the permissions we care about: ACE4_DELETE_CHILD is + * meaningless for non-directories, so we ignore it. + */ + x = ~ACE4_POSIX_ALWAYS_ALLOWED; + if (!S_ISDIR(*mode_p)) + x &= ~ACE4_DELETE_CHILD; + + mode = richacl_masks_to_mode(acl); + if ((acl->a_group_mask & x) != (richacl_mode_to_mask(mode >> 3) & x) || + (acl->a_other_mask & x) != (richacl_mode_to_mask(mode) & x)) + return -1; + + /* + * Ignore permissions which the owner is always allowed. + */ + x &= ~ACE4_POSIX_OWNER_ALLOWED; + if ((acl->a_owner_mask & x) != (richacl_mode_to_mask(mode >> 6) & x)) + return -1; + + if ((ace->e_mask & x) != (ACE4_POSIX_MODE_ALL & x)) + return -1; + + *mode_p = (*mode_p & ~S_IRWXUGO) | mode; + return 0; +} +EXPORT_SYMBOL_GPL(richacl_equiv_mode); diff --git a/include/linux/richacl.h b/include/linux/richacl.h index 630bf86..12a79f1 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -292,6 +292,7 @@ extern struct richacl *richacl_chmod(struct richacl *, mode_t); extern int richacl_permission(struct inode *, const struct richacl *, unsigned int); extern struct richacl *richacl_inherit(const struct richacl *, int); +extern int richacl_equiv_mode(const struct richacl *, mode_t *); /* richacl_inode.c */ extern struct richacl *richacl_inherit_inode(const struct richacl *, -- 1.7.1