From: Andreas Gruenbacher Subject: Re: [PATCH v23 09/22] richacl: Permission check algorithm Date: Mon, 11 Jul 2016 15:28:40 +0200 Message-ID: References: <1467294433-3222-1-git-send-email-agruenba@redhat.com> <1467294433-3222-10-git-send-email-agruenba@redhat.com> <1467730747.3800.34.camel@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Alexander Viro , Christoph Hellwig , "Theodore Ts'o" , Andreas Dilger , "J. Bruce Fields" , Trond Myklebust , Anna Schumaker , Dave Chinner , linux-ext4 , XFS Developers , LKML , linux-fsdevel , Linux NFS Mailing List , linux-cifs@vger.kernel.org, Linux API To: Jeff Layton Return-path: In-Reply-To: <1467730747.3800.34.camel@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Tue, Jul 5, 2016 at 4:59 PM, Jeff Layton wrote: > On Thu, 2016-06-30 at 15:47 +0200, Andreas Gruenbacher wrote: >> A richacl roughly grants a requested access if the NFSv4 acl in the >> richacl grants the requested permissions according to the NFSv4 >> permission check algorithm and the file mask that applies to the process >> includes the requested permissions. >> >> Signed-off-by: Andreas Gruenbacher >> Reviewed-by: J. Bruce Fields >> --- >> fs/richacl.c | 128 ++++++++++++++++++++++++++++++++++++++++++++++++ >> include/linux/richacl.h | 1 + >> 2 files changed, 129 insertions(+) >> >> diff --git a/fs/richacl.c b/fs/richacl.c >> index 056228f..cb0ef3f 100644 >> --- a/fs/richacl.c >> +++ b/fs/richacl.c >> @@ -338,3 +338,131 @@ restart: >> acl->a_flags &= ~(RICHACL_WRITE_THROUGH | RICHACL_MASKED); >> } >> EXPORT_SYMBOL_GPL(richacl_compute_max_masks); >> + >> +/** >> + * richacl_permission - richacl permission check algorithm >> + * @inode: inode to check >> + * @acl: rich acl of the inode >> + * @want: requested access (MAY_* flags) >> + * >> + * Checks if the current process is granted @mask flags in @acl. >> + */ > > nit: there is no @mask parm here. Do you mean @want ? Yes, thanks. >> +int >> +richacl_permission(struct inode *inode, const struct richacl *acl, >> + int want) >> +{ >> + const struct richace *ace; >> + unsigned int mask = richacl_want_to_mask(want); >> + unsigned int requested = mask, denied = 0; >> + int in_owning_group = in_group_p(inode->i_gid); >> + int in_owner_or_group_class = in_owning_group; >> + >> + /* >> + * A process is >> + * - in the owner file class if it owns the file, >> + * - in the group file class if it is in the file's owning group or >> + * it matches any of the user or group entries, and >> + * - in the other file class otherwise. >> + * The file class is only relevant for determining which file mask to >> + * apply, which only happens for masked acls. >> + */ >> + if (acl->a_flags & RICHACL_MASKED) { >> + if ((acl->a_flags & RICHACL_WRITE_THROUGH) && >> + uid_eq(current_fsuid(), inode->i_uid)) { >> + denied = requested & ~acl->a_owner_mask; >> + goto out; >> + } >> + } else { >> + /* >> + * When the acl is not masked, there is no need to determine if >> + * the process is in the group class and we can break out >> + * earlier of the loop below. >> + */ >> + in_owner_or_group_class = 1; >> + } >> + >> + /* >> + * Check if the acl grants the requested access and determine which >> + * file class the process is in. >> + */ >> + richacl_for_each_entry(ace, acl) { >> + unsigned int ace_mask = ace->e_mask; >> + >> + if (richace_is_inherit_only(ace)) >> + continue; >> + if (richace_is_owner(ace)) { >> + if (!uid_eq(current_fsuid(), inode->i_uid)) >> + continue; >> + goto entry_matches_owner; >> + } else if (richace_is_group(ace)) { >> + if (!in_owning_group) >> + continue; >> + } else if (richace_is_unix_user(ace)) { >> + if (!uid_eq(current_fsuid(), ace->e_id.uid)) >> + continue; >> + if (uid_eq(current_fsuid(), inode->i_uid)) >> + goto entry_matches_owner; >> + } else if (richace_is_unix_group(ace)) { >> + if (!in_group_p(ace->e_id.gid)) >> + continue; >> + } else >> + goto entry_matches_everyone; >> + >> + /* >> + * Apply the group file mask to entries other than owner@ and >> + * everyone@ or user entries matching the owner. This ensures >> + * that we grant the same permissions as the acl computed by >> + * richacl_apply_masks(). >> + * >> + * Without this restriction, the following richacl would grant >> + * rw access to processes which are both the owner and in the >> + * owning group, but not to other users in the owning group, >> + * which could not be represented without masks: >> + * >> + * owner:rw::mask >> + * group@:rw::allow >> + */ >> + if ((acl->a_flags & RICHACL_MASKED) && richace_is_allow(ace)) >> + ace_mask &= acl->a_group_mask; >> + >> +entry_matches_owner: >> + /* The process is in the owner or group file class. */ >> + in_owner_or_group_class = 1; >> + >> +entry_matches_everyone: >> + /* Check which mask flags the ACE allows or denies. */ >> + if (richace_is_deny(ace)) >> + denied |= ace_mask & mask; >> + mask &= ~ace_mask; >> + >> + /* >> + * Keep going until we know which file class >> + * the process is in. >> + */ >> + if (!mask && in_owner_or_group_class) >> + break; >> + } >> + denied |= mask; >> + >> + if (acl->a_flags & RICHACL_MASKED) { >> + /* >> + * The file class a process is in determines which file mask >> + * applies. Check if that file mask also grants the requested >> + * access. >> + */ >> + if (uid_eq(current_fsuid(), inode->i_uid)) >> + denied |= requested & ~acl->a_owner_mask; >> + else if (in_owner_or_group_class) >> + denied |= requested & ~acl->a_group_mask; >> + else { >> + if (acl->a_flags & RICHACL_WRITE_THROUGH) >> + denied = requested & ~acl->a_other_mask; >> + else >> + denied |= requested & ~acl->a_other_mask; >> + } >> + } >> + >> +out: >> + return denied ? -EACCES : 0; >> +} >> +EXPORT_SYMBOL_GPL(richacl_permission); >> diff --git a/include/linux/richacl.h b/include/linux/richacl.h >> index 3559b2c..be9fb65 100644 >> --- a/include/linux/richacl.h >> +++ b/include/linux/richacl.h >> @@ -179,5 +179,6 @@ extern int richacl_masks_to_mode(const struct richacl *); >> extern unsigned int richacl_mode_to_mask(umode_t); >> extern unsigned int richacl_want_to_mask(unsigned int); >> extern void richacl_compute_max_masks(struct richacl *); >> +extern int richacl_permission(struct inode *, const struct richacl *, int); >> >> #endif /* __RICHACL_H */ > > Reviewed-by: Jeff Layton Thanks, Andreas