From: Andreas Gruenbacher Subject: [PATCH v8 26/41] richacl: Apply the file masks to a richacl Date: Mon, 28 Sep 2015 00:09:17 +0200 Message-ID: <1443391772-10171-27-git-send-email-agruenba@redhat.com> References: <1443391772-10171-1-git-send-email-agruenba@redhat.com> To: Alexander Viro , "Theodore Ts'o" , Andreas Dilger , "J. Bruce Fields" , Jeff Layton , Trond Myklebust , Anna Schumaker , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-api@vger.kernel.org Return-path: In-Reply-To: <1443391772-10171-1-git-send-email-agruenba@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Put all the pieces of the acl transformation puzzle together for computing a richacl which has the file masks "applied" so that the standard nfsv4 access check algorithm can be used on the richacl. Signed-off-by: Andreas Gruenbacher Reviewed-by: J. Bruce Fields --- fs/richacl_compat.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/richacl.h | 3 ++ 2 files changed, 104 insertions(+) diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c index 7e25343..c99274f 100644 --- a/fs/richacl_compat.c +++ b/fs/richacl_compat.c @@ -726,3 +726,104 @@ richacl_isolate_group_class(struct richacl_alloc *alloc, unsigned int deny) } return 0; } + +/** + * __richacl_apply_masks - apply the file masks to all aces + * @alloc: acl and number of allocated entries + * + * Apply the owner mask to owner@ aces, the other mask to + * everyone@ aces, and the group mask to all other aces. + * + * The previous transformations have brought the acl into a + * form in which applying the masks will not lead to the + * accidental loss of permissions anymore. + */ +static int +__richacl_apply_masks(struct richacl_alloc *alloc, kuid_t owner) +{ + struct richace *ace; + + richacl_for_each_entry(ace, alloc->acl) { + unsigned int mask; + + if (richace_is_inherit_only(ace) || !richace_is_allow(ace)) + continue; + if (richace_is_owner(ace) || + (richace_is_unix_user(ace) && uid_eq(owner, ace->e_id.uid))) + mask = alloc->acl->a_owner_mask; + else if (richace_is_everyone(ace)) + mask = alloc->acl->a_other_mask; + else + mask = alloc->acl->a_group_mask; + if (richace_change_mask(alloc, &ace, ace->e_mask & mask)) + return -1; + } + return 0; +} + +/** + * richacl_apply_masks - apply the masks to the acl + * + * Transform @acl so that the standard NFSv4 permission check algorithm (which + * is not aware of file masks) will compute the same access decisions as the + * richacl permission check algorithm (which looks at the acl and the file + * masks). + * + * This algorithm is split into several steps: + * + * - Move everyone@ aces to the end of the acl. This simplifies the other + * transformations, and allows the everyone@ allow ace at the end of the + * acl to eventually allow permissions to the other class only. + * + * - Propagate everyone@ permissions up the acl. This transformation makes + * sure that the owner and group class aces won't lose any permissions when + * we apply the other mask to the everyone@ allow ace at the end of the acl. + * + * - Apply the file masks to all aces. + * + * - Make sure everyone is granted the other mask permissions. This step can + * elevate elevate permissions for the owner and group classes, which is + * corrected later. + * + * - Make sure that the group class is not granted any permissions from + * everyone@. + * + * - Make sure the owner is granted the owner mask permissions. + * + * - Make sure the owner is not granted any permissions beyond the owner + * mask from group class aces or from everyone@. + * + * NOTE: Depending on the acl and file masks, this algorithm can increase the + * number of aces by almost a factor of three in the worst case. This may make + * the acl too large for some purposes. + */ +int +richacl_apply_masks(struct richacl **acl, kuid_t owner) +{ + if ((*acl)->a_flags & RICHACL_MASKED) { + struct richacl_alloc alloc = { + .acl = richacl_clone(*acl, GFP_KERNEL), + .count = (*acl)->a_count, + }; + unsigned int added = 0; + + if (!alloc.acl) + return -ENOMEM; + if (richacl_move_everyone_aces_down(&alloc) || + richacl_propagate_everyone(&alloc) || + __richacl_apply_masks(&alloc, owner) || + richacl_set_other_permissions(&alloc, &added) || + richacl_isolate_group_class(&alloc, added) || + richacl_set_owner_permissions(&alloc) || + richacl_isolate_owner_class(&alloc)) { + richacl_put(alloc.acl); + return -ENOMEM; + } + + alloc.acl->a_flags &= ~(RICHACL_WRITE_THROUGH | RICHACL_MASKED); + richacl_put(*acl); + *acl = alloc.acl; + } + return 0; +} +EXPORT_SYMBOL_GPL(richacl_apply_masks); diff --git a/include/linux/richacl.h b/include/linux/richacl.h index 832b06c..a945f3c 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -332,4 +332,7 @@ extern struct richacl *richacl_inherit(const struct richacl *, int); extern int richacl_permission(struct inode *, const struct richacl *, int); extern struct richacl *richacl_create(struct inode *, struct inode *); +/* richacl_compat.c */ +extern int richacl_apply_masks(struct richacl **, kuid_t); + #endif /* __RICHACL_H */ -- 2.4.3