459 lines
13 KiB
C
Executable File
459 lines
13 KiB
C
Executable File
/*
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* AppArmor security module
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*
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* This file contains AppArmor mediation of files
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*
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* Copyright (C) 1998-2008 Novell/SUSE
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* Copyright 2009-2010 Canonical Ltd.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*/
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#include "include/apparmor.h"
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#include "include/audit.h"
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#include "include/file.h"
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#include "include/match.h"
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#include "include/path.h"
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#include "include/policy.h"
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struct file_perms nullperms;
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/**
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* audit_file_mask - convert mask to permission string
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* @buffer: buffer to write string to (NOT NULL)
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* @mask: permission mask to convert
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*/
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static void audit_file_mask(struct audit_buffer *ab, u32 mask)
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{
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char str[10];
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char *m = str;
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if (mask & AA_EXEC_MMAP)
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*m++ = 'm';
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if (mask & (MAY_READ | AA_MAY_META_READ))
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*m++ = 'r';
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if (mask & (MAY_WRITE | AA_MAY_META_WRITE | AA_MAY_CHMOD |
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AA_MAY_CHOWN))
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*m++ = 'w';
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else if (mask & MAY_APPEND)
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*m++ = 'a';
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if (mask & AA_MAY_CREATE)
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*m++ = 'c';
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if (mask & AA_MAY_DELETE)
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*m++ = 'd';
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if (mask & AA_MAY_LINK)
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*m++ = 'l';
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if (mask & AA_MAY_LOCK)
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*m++ = 'k';
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if (mask & MAY_EXEC)
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*m++ = 'x';
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*m = '\0';
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audit_log_string(ab, str);
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}
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/**
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* file_audit_cb - call back for file specific audit fields
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* @ab: audit_buffer (NOT NULL)
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* @va: audit struct to audit values of (NOT NULL)
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*/
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static void file_audit_cb(struct audit_buffer *ab, void *va)
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{
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struct common_audit_data *sa = va;
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kuid_t fsuid = current_fsuid();
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if (sa->aad->fs.request & AA_AUDIT_FILE_MASK) {
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audit_log_format(ab, " requested_mask=");
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audit_file_mask(ab, sa->aad->fs.request);
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}
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if (sa->aad->fs.denied & AA_AUDIT_FILE_MASK) {
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audit_log_format(ab, " denied_mask=");
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audit_file_mask(ab, sa->aad->fs.denied);
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}
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if (sa->aad->fs.request & AA_AUDIT_FILE_MASK) {
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audit_log_format(ab, " fsuid=%d",
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from_kuid(&init_user_ns, fsuid));
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audit_log_format(ab, " ouid=%d",
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from_kuid(&init_user_ns, sa->aad->fs.ouid));
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}
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if (sa->aad->fs.target) {
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audit_log_format(ab, " target=");
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audit_log_untrustedstring(ab, sa->aad->fs.target);
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}
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}
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/**
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* aa_audit_file - handle the auditing of file operations
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* @profile: the profile being enforced (NOT NULL)
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* @perms: the permissions computed for the request (NOT NULL)
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* @gfp: allocation flags
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* @op: operation being mediated
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* @request: permissions requested
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* @name: name of object being mediated (MAYBE NULL)
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* @target: name of target (MAYBE NULL)
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* @ouid: object uid
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* @info: extra information message (MAYBE NULL)
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* @error: 0 if operation allowed else failure error code
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*
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* Returns: %0 or error on failure
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*/
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int aa_audit_file(struct aa_profile *profile, struct file_perms *perms,
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gfp_t gfp, int op, u32 request, const char *name,
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const char *target, kuid_t ouid, const char *info, int error)
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{
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int type = AUDIT_APPARMOR_AUTO;
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struct common_audit_data sa;
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struct apparmor_audit_data aad = {0,};
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sa.type = LSM_AUDIT_DATA_NONE;
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sa.aad = &aad;
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aad.op = op,
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aad.fs.request = request;
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aad.name = name;
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aad.fs.target = target;
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aad.fs.ouid = ouid;
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aad.info = info;
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aad.error = error;
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if (likely(!sa.aad->error)) {
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u32 mask = perms->audit;
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if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
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mask = 0xffff;
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/* mask off perms that are not being force audited */
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sa.aad->fs.request &= mask;
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if (likely(!sa.aad->fs.request))
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return 0;
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type = AUDIT_APPARMOR_AUDIT;
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} else {
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/* only report permissions that were denied */
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sa.aad->fs.request = sa.aad->fs.request & ~perms->allow;
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if (sa.aad->fs.request & perms->kill)
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type = AUDIT_APPARMOR_KILL;
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/* quiet known rejects, assumes quiet and kill do not overlap */
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if ((sa.aad->fs.request & perms->quiet) &&
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AUDIT_MODE(profile) != AUDIT_NOQUIET &&
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AUDIT_MODE(profile) != AUDIT_ALL)
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sa.aad->fs.request &= ~perms->quiet;
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if (!sa.aad->fs.request)
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return COMPLAIN_MODE(profile) ? 0 : sa.aad->error;
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}
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sa.aad->fs.denied = sa.aad->fs.request & ~perms->allow;
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return aa_audit(type, profile, gfp, &sa, file_audit_cb);
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}
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/**
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* map_old_perms - map old file perms layout to the new layout
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* @old: permission set in old mapping
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*
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* Returns: new permission mapping
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*/
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static u32 map_old_perms(u32 old)
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{
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u32 new = old & 0xf;
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if (old & MAY_READ)
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new |= AA_MAY_META_READ;
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if (old & MAY_WRITE)
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new |= AA_MAY_META_WRITE | AA_MAY_CREATE | AA_MAY_DELETE |
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AA_MAY_CHMOD | AA_MAY_CHOWN;
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if (old & 0x10)
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new |= AA_MAY_LINK;
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/* the old mapping lock and link_subset flags where overlaid
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* and use was determined by part of a pair that they were in
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*/
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if (old & 0x20)
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new |= AA_MAY_LOCK | AA_LINK_SUBSET;
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if (old & 0x40) /* AA_EXEC_MMAP */
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new |= AA_EXEC_MMAP;
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return new;
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}
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/**
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* compute_perms - convert dfa compressed perms to internal perms
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* @dfa: dfa to compute perms for (NOT NULL)
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* @state: state in dfa
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* @cond: conditions to consider (NOT NULL)
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*
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* TODO: convert from dfa + state to permission entry, do computation conversion
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* at load time.
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*
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* Returns: computed permission set
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*/
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static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state,
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struct path_cond *cond)
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{
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struct file_perms perms;
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/* FIXME: change over to new dfa format
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* currently file perms are encoded in the dfa, new format
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* splits the permissions from the dfa. This mapping can be
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* done at profile load
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*/
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perms.kill = 0;
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if (uid_eq(current_fsuid(), cond->uid)) {
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perms.allow = map_old_perms(dfa_user_allow(dfa, state));
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perms.audit = map_old_perms(dfa_user_audit(dfa, state));
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perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
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perms.xindex = dfa_user_xindex(dfa, state);
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} else {
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perms.allow = map_old_perms(dfa_other_allow(dfa, state));
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perms.audit = map_old_perms(dfa_other_audit(dfa, state));
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perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
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perms.xindex = dfa_other_xindex(dfa, state);
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}
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perms.allow |= AA_MAY_META_READ;
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/* change_profile wasn't determined by ownership in old mapping */
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if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
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perms.allow |= AA_MAY_CHANGE_PROFILE;
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if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
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perms.allow |= AA_MAY_ONEXEC;
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return perms;
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}
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/**
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* aa_str_perms - find permission that match @name
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* @dfa: to match against (MAYBE NULL)
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* @state: state to start matching in
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* @name: string to match against dfa (NOT NULL)
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* @cond: conditions to consider for permission set computation (NOT NULL)
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* @perms: Returns - the permissions found when matching @name
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*
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* Returns: the final state in @dfa when beginning @start and walking @name
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*/
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unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
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const char *name, struct path_cond *cond,
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struct file_perms *perms)
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{
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unsigned int state;
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if (!dfa) {
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*perms = nullperms;
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return DFA_NOMATCH;
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}
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state = aa_dfa_match(dfa, start, name);
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*perms = compute_perms(dfa, state, cond);
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return state;
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}
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/**
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* is_deleted - test if a file has been completely unlinked
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* @dentry: dentry of file to test for deletion (NOT NULL)
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*
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* Returns: %1 if deleted else %0
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*/
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static inline bool is_deleted(struct dentry *dentry)
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{
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if (d_unlinked(dentry) && dentry->d_inode->i_nlink == 0)
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return 1;
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return 0;
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}
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/**
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* aa_path_perm - do permissions check & audit for @path
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* @op: operation being checked
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* @profile: profile being enforced (NOT NULL)
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* @path: path to check permissions of (NOT NULL)
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* @flags: any additional path flags beyond what the profile specifies
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* @request: requested permissions
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* @cond: conditional info for this request (NOT NULL)
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*
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* Returns: %0 else error if access denied or other error
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*/
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int aa_path_perm(int op, struct aa_profile *profile, struct path *path,
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int flags, u32 request, struct path_cond *cond)
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{
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char *buffer = NULL;
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struct file_perms perms = {};
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const char *name, *info = NULL;
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int error;
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flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
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error = aa_path_name(path, flags, &buffer, &name, &info);
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if (error) {
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if (error == -ENOENT && is_deleted(path->dentry)) {
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/* Access to open files that are deleted are
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* give a pass (implicit delegation)
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*/
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error = 0;
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info = NULL;
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perms.allow = request;
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}
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} else {
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aa_str_perms(profile->file.dfa, profile->file.start, name, cond,
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&perms);
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if (request & ~perms.allow)
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error = -EACCES;
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}
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error = aa_audit_file(profile, &perms, GFP_KERNEL, op, request, name,
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NULL, cond->uid, info, error);
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kfree(buffer);
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return error;
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}
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/**
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* xindex_is_subset - helper for aa_path_link
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* @link: link permission set
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* @target: target permission set
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*
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* test target x permissions are equal OR a subset of link x permissions
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* this is done as part of the subset test, where a hardlink must have
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* a subset of permissions that the target has.
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*
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* Returns: %1 if subset else %0
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*/
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static inline bool xindex_is_subset(u32 link, u32 target)
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{
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if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
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((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
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return 0;
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return 1;
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}
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/**
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* aa_path_link - Handle hard link permission check
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* @profile: the profile being enforced (NOT NULL)
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* @old_dentry: the target dentry (NOT NULL)
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* @new_dir: directory the new link will be created in (NOT NULL)
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* @new_dentry: the link being created (NOT NULL)
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*
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* Handle the permission test for a link & target pair. Permission
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* is encoded as a pair where the link permission is determined
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* first, and if allowed, the target is tested. The target test
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* is done from the point of the link match (not start of DFA)
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* making the target permission dependent on the link permission match.
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*
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* The subset test if required forces that permissions granted
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* on link are a subset of the permission granted to target.
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*
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* Returns: %0 if allowed else error
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*/
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int aa_path_link(struct aa_profile *profile, struct dentry *old_dentry,
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struct path *new_dir, struct dentry *new_dentry)
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{
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struct path link = { new_dir->mnt, new_dentry };
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struct path target = { new_dir->mnt, old_dentry };
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struct path_cond cond = {
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old_dentry->d_inode->i_uid,
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old_dentry->d_inode->i_mode
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};
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char *buffer = NULL, *buffer2 = NULL;
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const char *lname, *tname = NULL, *info = NULL;
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struct file_perms lperms, perms;
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u32 request = AA_MAY_LINK;
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unsigned int state;
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int error;
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lperms = nullperms;
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/* buffer freed below, lname is pointer in buffer */
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error = aa_path_name(&link, profile->path_flags, &buffer, &lname,
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&info);
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if (error)
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goto audit;
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/* buffer2 freed below, tname is pointer in buffer2 */
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error = aa_path_name(&target, profile->path_flags, &buffer2, &tname,
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&info);
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if (error)
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goto audit;
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error = -EACCES;
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/* aa_str_perms - handles the case of the dfa being NULL */
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state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
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&cond, &lperms);
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if (!(lperms.allow & AA_MAY_LINK))
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goto audit;
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/* test to see if target can be paired with link */
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state = aa_dfa_null_transition(profile->file.dfa, state);
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aa_str_perms(profile->file.dfa, state, tname, &cond, &perms);
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/* force audit/quiet masks for link are stored in the second entry
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* in the link pair.
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*/
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lperms.audit = perms.audit;
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lperms.quiet = perms.quiet;
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lperms.kill = perms.kill;
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if (!(perms.allow & AA_MAY_LINK)) {
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info = "target restricted";
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goto audit;
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}
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/* done if link subset test is not required */
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if (!(perms.allow & AA_LINK_SUBSET))
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goto done_tests;
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/* Do link perm subset test requiring allowed permission on link are a
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* subset of the allowed permissions on target.
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*/
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aa_str_perms(profile->file.dfa, profile->file.start, tname, &cond,
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&perms);
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/* AA_MAY_LINK is not considered in the subset test */
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request = lperms.allow & ~AA_MAY_LINK;
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lperms.allow &= perms.allow | AA_MAY_LINK;
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request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
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if (request & ~lperms.allow) {
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goto audit;
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} else if ((lperms.allow & MAY_EXEC) &&
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!xindex_is_subset(lperms.xindex, perms.xindex)) {
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lperms.allow &= ~MAY_EXEC;
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request |= MAY_EXEC;
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info = "link not subset of target";
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goto audit;
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}
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done_tests:
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error = 0;
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audit:
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error = aa_audit_file(profile, &lperms, GFP_KERNEL, OP_LINK, request,
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lname, tname, cond.uid, info, error);
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kfree(buffer);
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kfree(buffer2);
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return error;
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}
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/**
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* aa_file_perm - do permission revalidation check & audit for @file
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* @op: operation being checked
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* @profile: profile being enforced (NOT NULL)
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* @file: file to revalidate access permissions on (NOT NULL)
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* @request: requested permissions
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*
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* Returns: %0 if access allowed else error
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*/
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int aa_file_perm(int op, struct aa_profile *profile, struct file *file,
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u32 request)
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{
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struct path_cond cond = {
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.uid = file_inode(file)->i_uid,
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.mode = file_inode(file)->i_mode
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};
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return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,
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request, &cond);
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}
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