diff options
Diffstat (limited to 'security/device_cgroup.c')
| -rw-r--r-- | security/device_cgroup.c | 793 |
1 files changed, 561 insertions, 232 deletions
diff --git a/security/device_cgroup.c b/security/device_cgroup.c index 8b5b5d8612c..d9d69e6930e 100644 --- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -25,13 +25,19 @@ static DEFINE_MUTEX(devcgroup_mutex); +enum devcg_behavior { + DEVCG_DEFAULT_NONE, + DEVCG_DEFAULT_ALLOW, + DEVCG_DEFAULT_DENY, +}; + /* - * whitelist locking rules: + * exception list locking rules: * hold devcgroup_mutex for update/read. * hold rcu_read_lock() for read. */ -struct dev_whitelist_item { +struct dev_exception_item { u32 major, minor; short type; short access; @@ -41,45 +47,31 @@ struct dev_whitelist_item { struct dev_cgroup { struct cgroup_subsys_state css; - struct list_head whitelist; + struct list_head exceptions; + enum devcg_behavior behavior; }; static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) { - return container_of(s, struct dev_cgroup, css); -} - -static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup) -{ - return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id)); + return s ? container_of(s, struct dev_cgroup, css) : NULL; } static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) { - return css_to_devcgroup(task_subsys_state(task, devices_subsys_id)); -} - -struct cgroup_subsys devices_subsys; - -static int devcgroup_can_attach(struct cgroup_subsys *ss, - struct cgroup *new_cgrp, struct cgroup_taskset *set) -{ - struct task_struct *task = cgroup_taskset_first(set); - - if (current != task && !capable(CAP_SYS_ADMIN)) - return -EPERM; - return 0; + return css_to_devcgroup(task_css(task, devices_cgrp_id)); } /* * called under devcgroup_mutex */ -static int dev_whitelist_copy(struct list_head *dest, struct list_head *orig) +static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig) { - struct dev_whitelist_item *wh, *tmp, *new; + struct dev_exception_item *ex, *tmp, *new; - list_for_each_entry(wh, orig, list) { - new = kmemdup(wh, sizeof(*wh), GFP_KERNEL); + lockdep_assert_held(&devcgroup_mutex); + + list_for_each_entry(ex, orig, list) { + new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); if (!new) goto free_and_exit; list_add_tail(&new->list, dest); @@ -88,64 +80,64 @@ static int dev_whitelist_copy(struct list_head *dest, struct list_head *orig) return 0; free_and_exit: - list_for_each_entry_safe(wh, tmp, dest, list) { - list_del(&wh->list); - kfree(wh); + list_for_each_entry_safe(ex, tmp, dest, list) { + list_del(&ex->list); + kfree(ex); } return -ENOMEM; } -/* Stupid prototype - don't bother combining existing entries */ /* * called under devcgroup_mutex */ -static int dev_whitelist_add(struct dev_cgroup *dev_cgroup, - struct dev_whitelist_item *wh) +static int dev_exception_add(struct dev_cgroup *dev_cgroup, + struct dev_exception_item *ex) { - struct dev_whitelist_item *whcopy, *walk; + struct dev_exception_item *excopy, *walk; + + lockdep_assert_held(&devcgroup_mutex); - whcopy = kmemdup(wh, sizeof(*wh), GFP_KERNEL); - if (!whcopy) + excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); + if (!excopy) return -ENOMEM; - list_for_each_entry(walk, &dev_cgroup->whitelist, list) { - if (walk->type != wh->type) + list_for_each_entry(walk, &dev_cgroup->exceptions, list) { + if (walk->type != ex->type) continue; - if (walk->major != wh->major) + if (walk->major != ex->major) continue; - if (walk->minor != wh->minor) + if (walk->minor != ex->minor) continue; - walk->access |= wh->access; - kfree(whcopy); - whcopy = NULL; + walk->access |= ex->access; + kfree(excopy); + excopy = NULL; } - if (whcopy != NULL) - list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist); + if (excopy != NULL) + list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); return 0; } /* * called under devcgroup_mutex */ -static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup, - struct dev_whitelist_item *wh) +static void dev_exception_rm(struct dev_cgroup *dev_cgroup, + struct dev_exception_item *ex) { - struct dev_whitelist_item *walk, *tmp; + struct dev_exception_item *walk, *tmp; + + lockdep_assert_held(&devcgroup_mutex); - list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) { - if (walk->type == DEV_ALL) - goto remove; - if (walk->type != wh->type) + list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { + if (walk->type != ex->type) continue; - if (walk->major != ~0 && walk->major != wh->major) + if (walk->major != ex->major) continue; - if (walk->minor != ~0 && walk->minor != wh->minor) + if (walk->minor != ex->minor) continue; -remove: - walk->access &= ~wh->access; + walk->access &= ~ex->access; if (!walk->access) { list_del_rcu(&walk->list); kfree_rcu(walk, rcu); @@ -153,59 +145,92 @@ remove: } } +static void __dev_exception_clean(struct dev_cgroup *dev_cgroup) +{ + struct dev_exception_item *ex, *tmp; + + list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { + list_del_rcu(&ex->list); + kfree_rcu(ex, rcu); + } +} + +/** + * dev_exception_clean - frees all entries of the exception list + * @dev_cgroup: dev_cgroup with the exception list to be cleaned + * + * called under devcgroup_mutex + */ +static void dev_exception_clean(struct dev_cgroup *dev_cgroup) +{ + lockdep_assert_held(&devcgroup_mutex); + + __dev_exception_clean(dev_cgroup); +} + +static inline bool is_devcg_online(const struct dev_cgroup *devcg) +{ + return (devcg->behavior != DEVCG_DEFAULT_NONE); +} + +/** + * devcgroup_online - initializes devcgroup's behavior and exceptions based on + * parent's + * @css: css getting online + * returns 0 in case of success, error code otherwise + */ +static int devcgroup_online(struct cgroup_subsys_state *css) +{ + struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); + struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent); + int ret = 0; + + mutex_lock(&devcgroup_mutex); + + if (parent_dev_cgroup == NULL) + dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; + else { + ret = dev_exceptions_copy(&dev_cgroup->exceptions, + &parent_dev_cgroup->exceptions); + if (!ret) + dev_cgroup->behavior = parent_dev_cgroup->behavior; + } + mutex_unlock(&devcgroup_mutex); + + return ret; +} + +static void devcgroup_offline(struct cgroup_subsys_state *css) +{ + struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); + + mutex_lock(&devcgroup_mutex); + dev_cgroup->behavior = DEVCG_DEFAULT_NONE; + mutex_unlock(&devcgroup_mutex); +} + /* * called from kernel/cgroup.c with cgroup_lock() held. */ -static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss, - struct cgroup *cgroup) +static struct cgroup_subsys_state * +devcgroup_css_alloc(struct cgroup_subsys_state *parent_css) { - struct dev_cgroup *dev_cgroup, *parent_dev_cgroup; - struct cgroup *parent_cgroup; - int ret; + struct dev_cgroup *dev_cgroup; dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); if (!dev_cgroup) return ERR_PTR(-ENOMEM); - INIT_LIST_HEAD(&dev_cgroup->whitelist); - parent_cgroup = cgroup->parent; - - if (parent_cgroup == NULL) { - struct dev_whitelist_item *wh; - wh = kmalloc(sizeof(*wh), GFP_KERNEL); - if (!wh) { - kfree(dev_cgroup); - return ERR_PTR(-ENOMEM); - } - wh->minor = wh->major = ~0; - wh->type = DEV_ALL; - wh->access = ACC_MASK; - list_add(&wh->list, &dev_cgroup->whitelist); - } else { - parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup); - mutex_lock(&devcgroup_mutex); - ret = dev_whitelist_copy(&dev_cgroup->whitelist, - &parent_dev_cgroup->whitelist); - mutex_unlock(&devcgroup_mutex); - if (ret) { - kfree(dev_cgroup); - return ERR_PTR(ret); - } - } + INIT_LIST_HEAD(&dev_cgroup->exceptions); + dev_cgroup->behavior = DEVCG_DEFAULT_NONE; return &dev_cgroup->css; } -static void devcgroup_destroy(struct cgroup_subsys *ss, - struct cgroup *cgroup) +static void devcgroup_css_free(struct cgroup_subsys_state *css) { - struct dev_cgroup *dev_cgroup; - struct dev_whitelist_item *wh, *tmp; + struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); - dev_cgroup = cgroup_to_devcgroup(cgroup); - list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) { - list_del(&wh->list); - kfree(wh); - } + __dev_exception_clean(dev_cgroup); kfree(dev_cgroup); } @@ -247,112 +272,384 @@ static void set_majmin(char *str, unsigned m) sprintf(str, "%u", m); } -static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, - struct seq_file *m) +static int devcgroup_seq_show(struct seq_file *m, void *v) { - struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup); - struct dev_whitelist_item *wh; + struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m)); + struct dev_exception_item *ex; char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; rcu_read_lock(); - list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) { - set_access(acc, wh->access); - set_majmin(maj, wh->major); - set_majmin(min, wh->minor); - seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type), + /* + * To preserve the compatibility: + * - Only show the "all devices" when the default policy is to allow + * - List the exceptions in case the default policy is to deny + * This way, the file remains as a "whitelist of devices" + */ + if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { + set_access(acc, ACC_MASK); + set_majmin(maj, ~0); + set_majmin(min, ~0); + seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL), maj, min, acc); + } else { + list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { + set_access(acc, ex->access); + set_majmin(maj, ex->major); + set_majmin(min, ex->minor); + seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), + maj, min, acc); + } } rcu_read_unlock(); return 0; } -/* - * may_access_whitelist: - * does the access granted to dev_cgroup c contain the access - * requested in whitelist item refwh. - * return 1 if yes, 0 if no. - * call with devcgroup_mutex held +/** + * match_exception - iterates the exception list trying to find a complete match + * @exceptions: list of exceptions + * @type: device type (DEV_BLOCK or DEV_CHAR) + * @major: device file major number, ~0 to match all + * @minor: device file minor number, ~0 to match all + * @access: permission mask (ACC_READ, ACC_WRITE, ACC_MKNOD) + * + * It is considered a complete match if an exception is found that will + * contain the entire range of provided parameters. + * + * Return: true in case it matches an exception completely */ -static int may_access_whitelist(struct dev_cgroup *c, - struct dev_whitelist_item *refwh) +static bool match_exception(struct list_head *exceptions, short type, + u32 major, u32 minor, short access) { - struct dev_whitelist_item *whitem; + struct dev_exception_item *ex; - list_for_each_entry(whitem, &c->whitelist, list) { - if (whitem->type & DEV_ALL) - return 1; - if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK)) + list_for_each_entry_rcu(ex, exceptions, list) { + if ((type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) continue; - if ((refwh->type & DEV_CHAR) && !(whitem->type & DEV_CHAR)) + if ((type & DEV_CHAR) && !(ex->type & DEV_CHAR)) continue; - if (whitem->major != ~0 && whitem->major != refwh->major) + if (ex->major != ~0 && ex->major != major) continue; - if (whitem->minor != ~0 && whitem->minor != refwh->minor) + if (ex->minor != ~0 && ex->minor != minor) continue; - if (refwh->access & (~whitem->access)) + /* provided access cannot have more than the exception rule */ + if (access & (~ex->access)) continue; - return 1; + return true; } - return 0; + return false; +} + +/** + * match_exception_partial - iterates the exception list trying to find a partial match + * @exceptions: list of exceptions + * @type: device type (DEV_BLOCK or DEV_CHAR) + * @major: device file major number, ~0 to match all + * @minor: device file minor number, ~0 to match all + * @access: permission mask (ACC_READ, ACC_WRITE, ACC_MKNOD) + * + * It is considered a partial match if an exception's range is found to + * contain *any* of the devices specified by provided parameters. This is + * used to make sure no extra access is being granted that is forbidden by + * any of the exception list. + * + * Return: true in case the provided range mat matches an exception completely + */ +static bool match_exception_partial(struct list_head *exceptions, short type, + u32 major, u32 minor, short access) +{ + struct dev_exception_item *ex; + + list_for_each_entry_rcu(ex, exceptions, list) { + if ((type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) + continue; + if ((type & DEV_CHAR) && !(ex->type & DEV_CHAR)) + continue; + /* + * We must be sure that both the exception and the provided + * range aren't masking all devices + */ + if (ex->major != ~0 && major != ~0 && ex->major != major) + continue; + if (ex->minor != ~0 && minor != ~0 && ex->minor != minor) + continue; + /* + * In order to make sure the provided range isn't matching + * an exception, all its access bits shouldn't match the + * exception's access bits + */ + if (!(access & ex->access)) + continue; + return true; + } + return false; +} + +/** + * verify_new_ex - verifies if a new exception is allowed by parent cgroup's permissions + * @dev_cgroup: dev cgroup to be tested against + * @refex: new exception + * @behavior: behavior of the exception's dev_cgroup + * + * This is used to make sure a child cgroup won't have more privileges + * than its parent + */ +static bool verify_new_ex(struct dev_cgroup *dev_cgroup, + struct dev_exception_item *refex, + enum devcg_behavior behavior) +{ + bool match = false; + + rcu_lockdep_assert(rcu_read_lock_held() || + lockdep_is_held(&devcgroup_mutex), + "device_cgroup:verify_new_ex called without proper synchronization"); + + if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { + if (behavior == DEVCG_DEFAULT_ALLOW) { + /* + * new exception in the child doesn't matter, only + * adding extra restrictions + */ + return true; + } else { + /* + * new exception in the child will add more devices + * that can be acessed, so it can't match any of + * parent's exceptions, even slightly + */ + match = match_exception_partial(&dev_cgroup->exceptions, + refex->type, + refex->major, + refex->minor, + refex->access); + + if (match) + return false; + return true; + } + } else { + /* + * Only behavior == DEVCG_DEFAULT_DENY allowed here, therefore + * the new exception will add access to more devices and must + * be contained completely in an parent's exception to be + * allowed + */ + match = match_exception(&dev_cgroup->exceptions, refex->type, + refex->major, refex->minor, + refex->access); + + if (match) + /* parent has an exception that matches the proposed */ + return true; + else + return false; + } + return false; } /* * parent_has_perm: - * when adding a new allow rule to a device whitelist, the rule + * when adding a new allow rule to a device exception list, the rule * must be allowed in the parent device */ static int parent_has_perm(struct dev_cgroup *childcg, - struct dev_whitelist_item *wh) + struct dev_exception_item *ex) { - struct cgroup *pcg = childcg->css.cgroup->parent; - struct dev_cgroup *parent; + struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); + + if (!parent) + return 1; + return verify_new_ex(parent, ex, childcg->behavior); +} + +/** + * parent_allows_removal - verify if it's ok to remove an exception + * @childcg: child cgroup from where the exception will be removed + * @ex: exception being removed + * + * When removing an exception in cgroups with default ALLOW policy, it must + * be checked if removing it will give the child cgroup more access than the + * parent. + * + * Return: true if it's ok to remove exception, false otherwise + */ +static bool parent_allows_removal(struct dev_cgroup *childcg, + struct dev_exception_item *ex) +{ + struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); + + if (!parent) + return true; - if (!pcg) + /* It's always allowed to remove access to devices */ + if (childcg->behavior == DEVCG_DEFAULT_DENY) + return true; + + /* + * Make sure you're not removing part or a whole exception existing in + * the parent cgroup + */ + return !match_exception_partial(&parent->exceptions, ex->type, + ex->major, ex->minor, ex->access); +} + +/** + * may_allow_all - checks if it's possible to change the behavior to + * allow based on parent's rules. + * @parent: device cgroup's parent + * returns: != 0 in case it's allowed, 0 otherwise + */ +static inline int may_allow_all(struct dev_cgroup *parent) +{ + if (!parent) return 1; - parent = cgroup_to_devcgroup(pcg); - return may_access_whitelist(parent, wh); + return parent->behavior == DEVCG_DEFAULT_ALLOW; +} + +/** + * revalidate_active_exceptions - walks through the active exception list and + * revalidates the exceptions based on parent's + * behavior and exceptions. The exceptions that + * are no longer valid will be removed. + * Called with devcgroup_mutex held. + * @devcg: cgroup which exceptions will be checked + * + * This is one of the three key functions for hierarchy implementation. + * This function is responsible for re-evaluating all the cgroup's active + * exceptions due to a parent's exception change. + * Refer to Documentation/cgroups/devices.txt for more details. + */ +static void revalidate_active_exceptions(struct dev_cgroup *devcg) +{ + struct dev_exception_item *ex; + struct list_head *this, *tmp; + + list_for_each_safe(this, tmp, &devcg->exceptions) { + ex = container_of(this, struct dev_exception_item, list); + if (!parent_has_perm(devcg, ex)) + dev_exception_rm(devcg, ex); + } +} + +/** + * propagate_exception - propagates a new exception to the children + * @devcg_root: device cgroup that added a new exception + * @ex: new exception to be propagated + * + * returns: 0 in case of success, != 0 in case of error + */ +static int propagate_exception(struct dev_cgroup *devcg_root, + struct dev_exception_item *ex) +{ + struct cgroup_subsys_state *pos; + int rc = 0; + + rcu_read_lock(); + + css_for_each_descendant_pre(pos, &devcg_root->css) { + struct dev_cgroup *devcg = css_to_devcgroup(pos); + + /* + * Because devcgroup_mutex is held, no devcg will become + * online or offline during the tree walk (see on/offline + * methods), and online ones are safe to access outside RCU + * read lock without bumping refcnt. + */ + if (pos == &devcg_root->css || !is_devcg_online(devcg)) + continue; + + rcu_read_unlock(); + + /* + * in case both root's behavior and devcg is allow, a new + * restriction means adding to the exception list + */ + if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW && + devcg->behavior == DEVCG_DEFAULT_ALLOW) { + rc = dev_exception_add(devcg, ex); + if (rc) + break; + } else { + /* + * in the other possible cases: + * root's behavior: allow, devcg's: deny + * root's behavior: deny, devcg's: deny + * the exception will be removed + */ + dev_exception_rm(devcg, ex); + } + revalidate_active_exceptions(devcg); + + rcu_read_lock(); + } + + rcu_read_unlock(); + return rc; } /* - * Modify the whitelist using allow/deny rules. + * Modify the exception list using allow/deny rules. * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD * so we can give a container CAP_MKNOD to let it create devices but not - * modify the whitelist. + * modify the exception list. * It seems likely we'll want to add a CAP_CONTAINER capability to allow * us to also grant CAP_SYS_ADMIN to containers without giving away the - * device whitelist controls, but for now we'll stick with CAP_SYS_ADMIN + * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN * * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting * new access is only allowed if you're in the top-level cgroup, or your * parent cgroup has the access you're asking for. */ static int devcgroup_update_access(struct dev_cgroup *devcgroup, - int filetype, const char *buffer) + int filetype, char *buffer) { const char *b; - char *endp; - int count; - struct dev_whitelist_item wh; + char temp[12]; /* 11 + 1 characters needed for a u32 */ + int count, rc = 0; + struct dev_exception_item ex; + struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent); if (!capable(CAP_SYS_ADMIN)) return -EPERM; - memset(&wh, 0, sizeof(wh)); + memset(&ex, 0, sizeof(ex)); b = buffer; switch (*b) { case 'a': - wh.type = DEV_ALL; - wh.access = ACC_MASK; - wh.major = ~0; - wh.minor = ~0; - goto handle; + switch (filetype) { + case DEVCG_ALLOW: + if (css_has_online_children(&devcgroup->css)) + return -EINVAL; + + if (!may_allow_all(parent)) + return -EPERM; + dev_exception_clean(devcgroup); + devcgroup->behavior = DEVCG_DEFAULT_ALLOW; + if (!parent) + break; + + rc = dev_exceptions_copy(&devcgroup->exceptions, + &parent->exceptions); + if (rc) + return rc; + break; + case DEVCG_DENY: + if (css_has_online_children(&devcgroup->css)) + return -EINVAL; + + dev_exception_clean(devcgroup); + devcgroup->behavior = DEVCG_DEFAULT_DENY; + break; + default: + return -EINVAL; + } + return 0; case 'b': - wh.type = DEV_BLOCK; + ex.type = DEV_BLOCK; break; case 'c': - wh.type = DEV_CHAR; + ex.type = DEV_CHAR; break; default: return -EINVAL; @@ -362,11 +659,19 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, return -EINVAL; b++; if (*b == '*') { - wh.major = ~0; + ex.major = ~0; b++; } else if (isdigit(*b)) { - wh.major = simple_strtoul(b, &endp, 10); - b = endp; + memset(temp, 0, sizeof(temp)); + for (count = 0; count < sizeof(temp) - 1; count++) { + temp[count] = *b; + b++; + if (!isdigit(*b)) + break; + } + rc = kstrtou32(temp, 10, &ex.major); + if (rc) + return -EINVAL; } else { return -EINVAL; } @@ -376,11 +681,19 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, /* read minor */ if (*b == '*') { - wh.minor = ~0; + ex.minor = ~0; b++; } else if (isdigit(*b)) { - wh.minor = simple_strtoul(b, &endp, 10); - b = endp; + memset(temp, 0, sizeof(temp)); + for (count = 0; count < sizeof(temp) - 1; count++) { + temp[count] = *b; + b++; + if (!isdigit(*b)) + break; + } + rc = kstrtou32(temp, 10, &ex.minor); + if (rc) + return -EINVAL; } else { return -EINVAL; } @@ -389,13 +702,13 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, for (b++, count = 0; count < 3; count++, b++) { switch (*b) { case 'r': - wh.access |= ACC_READ; + ex.access |= ACC_READ; break; case 'w': - wh.access |= ACC_WRITE; + ex.access |= ACC_WRITE; break; case 'm': - wh.access |= ACC_MKNOD; + ex.access |= ACC_MKNOD; break; case '\n': case '\0': @@ -406,134 +719,150 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, } } -handle: switch (filetype) { case DEVCG_ALLOW: - if (!parent_has_perm(devcgroup, &wh)) + /* + * If the default policy is to allow by default, try to remove + * an matching exception instead. And be silent about it: we + * don't want to break compatibility + */ + if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { + /* Check if the parent allows removing it first */ + if (!parent_allows_removal(devcgroup, &ex)) + return -EPERM; + dev_exception_rm(devcgroup, &ex); + break; + } + + if (!parent_has_perm(devcgroup, &ex)) return -EPERM; - return dev_whitelist_add(devcgroup, &wh); + rc = dev_exception_add(devcgroup, &ex); + break; case DEVCG_DENY: - dev_whitelist_rm(devcgroup, &wh); + /* + * If the default policy is to deny by default, try to remove + * an matching exception instead. And be silent about it: we + * don't want to break compatibility + */ + if (devcgroup->behavior == DEVCG_DEFAULT_DENY) + dev_exception_rm(devcgroup, &ex); + else + rc = dev_exception_add(devcgroup, &ex); + + if (rc) + break; + /* we only propagate new restrictions */ + rc = propagate_exception(devcgroup, &ex); break; default: - return -EINVAL; + rc = -EINVAL; } - return 0; + return rc; } -static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft, - const char *buffer) +static ssize_t devcgroup_access_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off) { int retval; mutex_lock(&devcgroup_mutex); - retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp), - cft->private, buffer); + retval = devcgroup_update_access(css_to_devcgroup(of_css(of)), + of_cft(of)->private, strstrip(buf)); mutex_unlock(&devcgroup_mutex); - return retval; + return retval ?: nbytes; } static struct cftype dev_cgroup_files[] = { { .name = "allow", - .write_string = devcgroup_access_write, + .write = devcgroup_access_write, .private = DEVCG_ALLOW, }, { .name = "deny", - .write_string = devcgroup_access_write, + .write = devcgroup_access_write, .private = DEVCG_DENY, }, { .name = "list", - .read_seq_string = devcgroup_seq_read, + .seq_show = devcgroup_seq_show, .private = DEVCG_LIST, }, + { } /* terminate */ }; -static int devcgroup_populate(struct cgroup_subsys *ss, - struct cgroup *cgroup) -{ - return cgroup_add_files(cgroup, ss, dev_cgroup_files, - ARRAY_SIZE(dev_cgroup_files)); -} - -struct cgroup_subsys devices_subsys = { - .name = "devices", - .can_attach = devcgroup_can_attach, - .create = devcgroup_create, - .destroy = devcgroup_destroy, - .populate = devcgroup_populate, - .subsys_id = devices_subsys_id, +struct cgroup_subsys devices_cgrp_subsys = { + .css_alloc = devcgroup_css_alloc, + .css_free = devcgroup_css_free, + .css_online = devcgroup_online, + .css_offline = devcgroup_offline, + .base_cftypes = dev_cgroup_files, }; -int __devcgroup_inode_permission(struct inode *inode, int mask) +/** + * __devcgroup_check_permission - checks if an inode operation is permitted + * @dev_cgroup: the dev cgroup to be tested against + * @type: device type + * @major: device major number + * @minor: device minor number + * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD + * + * returns 0 on success, -EPERM case the operation is not permitted + */ +static int __devcgroup_check_permission(short type, u32 major, u32 minor, + short access) { struct dev_cgroup *dev_cgroup; - struct dev_whitelist_item *wh; + bool rc; rcu_read_lock(); - dev_cgroup = task_devcgroup(current); + if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) + /* Can't match any of the exceptions, even partially */ + rc = !match_exception_partial(&dev_cgroup->exceptions, + type, major, minor, access); + else + /* Need to match completely one exception to be allowed */ + rc = match_exception(&dev_cgroup->exceptions, type, major, + minor, access); + rcu_read_unlock(); - list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { - if (wh->type & DEV_ALL) - goto found; - if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode)) - continue; - if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode)) - continue; - if (wh->major != ~0 && wh->major != imajor(inode)) - continue; - if (wh->minor != ~0 && wh->minor != iminor(inode)) - continue; - - if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE)) - continue; - if ((mask & MAY_READ) && !(wh->access & ACC_READ)) - continue; -found: - rcu_read_unlock(); - return 0; - } + if (!rc) + return -EPERM; - rcu_read_unlock(); + return 0; +} - return -EPERM; +int __devcgroup_inode_permission(struct inode *inode, int mask) +{ + short type, access = 0; + + if (S_ISBLK(inode->i_mode)) + type = DEV_BLOCK; + if (S_ISCHR(inode->i_mode)) + type = DEV_CHAR; + if (mask & MAY_WRITE) + access |= ACC_WRITE; + if (mask & MAY_READ) + access |= ACC_READ; + + return __devcgroup_check_permission(type, imajor(inode), iminor(inode), + access); } int devcgroup_inode_mknod(int mode, dev_t dev) { - struct dev_cgroup *dev_cgroup; - struct dev_whitelist_item *wh; + short type; if (!S_ISBLK(mode) && !S_ISCHR(mode)) return 0; - rcu_read_lock(); - - dev_cgroup = task_devcgroup(current); - - list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { - if (wh->type & DEV_ALL) - goto found; - if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode)) - continue; - if ((wh->type & DEV_CHAR) && !S_ISCHR(mode)) - continue; - if (wh->major != ~0 && wh->major != MAJOR(dev)) - continue; - if (wh->minor != ~0 && wh->minor != MINOR(dev)) - continue; - - if (!(wh->access & ACC_MKNOD)) - continue; -found: - rcu_read_unlock(); - return 0; - } + if (S_ISBLK(mode)) + type = DEV_BLOCK; + else + type = DEV_CHAR; - rcu_read_unlock(); + return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev), + ACC_MKNOD); - return -EPERM; } |