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-rw-r--r--security/device_cgroup.c87
1 files changed, 61 insertions, 26 deletions
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 44dfc41..842c254 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -42,7 +42,10 @@ struct dev_exception_item {
struct dev_cgroup {
struct cgroup_subsys_state css;
struct list_head exceptions;
- bool deny_all;
+ enum {
+ DEVCG_DEFAULT_ALLOW,
+ DEVCG_DEFAULT_DENY,
+ } behavior;
};
static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
@@ -182,13 +185,13 @@ static struct cgroup_subsys_state *devcgroup_create(struct cgroup *cgroup)
parent_cgroup = cgroup->parent;
if (parent_cgroup == NULL)
- dev_cgroup->deny_all = false;
+ dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
else {
parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup);
mutex_lock(&devcgroup_mutex);
ret = dev_exceptions_copy(&dev_cgroup->exceptions,
&parent_dev_cgroup->exceptions);
- dev_cgroup->deny_all = parent_dev_cgroup->deny_all;
+ dev_cgroup->behavior = parent_dev_cgroup->behavior;
mutex_unlock(&devcgroup_mutex);
if (ret) {
kfree(dev_cgroup);
@@ -260,7 +263,7 @@ static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
* - List the exceptions in case the default policy is to deny
* This way, the file remains as a "whitelist of devices"
*/
- if (devcgroup->deny_all == false) {
+ if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
set_access(acc, ACC_MASK);
set_majmin(maj, ~0);
set_majmin(min, ~0);
@@ -314,12 +317,12 @@ static int may_access(struct dev_cgroup *dev_cgroup,
* In two cases we'll consider this new exception valid:
* - the dev cgroup has its default policy to allow + exception list:
* the new exception should *not* match any of the exceptions
- * (!deny_all, !match)
+ * (behavior == DEVCG_DEFAULT_ALLOW, !match)
* - the dev cgroup has its default policy to deny + exception list:
* the new exception *should* match the exceptions
- * (deny_all, match)
+ * (behavior == DEVCG_DEFAULT_DENY, match)
*/
- if (dev_cgroup->deny_all == match)
+ if ((dev_cgroup->behavior == DEVCG_DEFAULT_DENY) == match)
return 1;
return 0;
}
@@ -341,6 +344,17 @@ static int parent_has_perm(struct dev_cgroup *childcg,
return may_access(parent, ex);
}
+/**
+ * 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)
+{
+ return parent->behavior == DEVCG_DEFAULT_ALLOW;
+}
+
/*
* Modify the exception list using allow/deny rules.
* CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
@@ -358,9 +372,11 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
int filetype, const char *buffer)
{
const char *b;
- char *endp;
- int count;
+ char temp[12]; /* 11 + 1 characters needed for a u32 */
+ int count, rc;
struct dev_exception_item ex;
+ struct cgroup *p = devcgroup->css.cgroup;
+ struct dev_cgroup *parent = cgroup_to_devcgroup(p->parent);
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
@@ -372,14 +388,18 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
case 'a':
switch (filetype) {
case DEVCG_ALLOW:
- if (!parent_has_perm(devcgroup, &ex))
+ if (!may_allow_all(parent))
return -EPERM;
dev_exception_clean(devcgroup);
- devcgroup->deny_all = false;
+ rc = dev_exceptions_copy(&devcgroup->exceptions,
+ &parent->exceptions);
+ if (rc)
+ return rc;
+ devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
break;
case DEVCG_DENY:
dev_exception_clean(devcgroup);
- devcgroup->deny_all = true;
+ devcgroup->behavior = DEVCG_DEFAULT_DENY;
break;
default:
return -EINVAL;
@@ -402,8 +422,16 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
ex.major = ~0;
b++;
} else if (isdigit(*b)) {
- ex.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;
}
@@ -416,8 +444,16 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
ex.minor = ~0;
b++;
} else if (isdigit(*b)) {
- ex.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;
}
@@ -452,7 +488,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
* an matching exception instead. And be silent about it: we
* don't want to break compatibility
*/
- if (devcgroup->deny_all == false) {
+ if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
dev_exception_rm(devcgroup, &ex);
return 0;
}
@@ -463,7 +499,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
* an matching exception instead. And be silent about it: we
* don't want to break compatibility
*/
- if (devcgroup->deny_all == true) {
+ if (devcgroup->behavior == DEVCG_DEFAULT_DENY) {
dev_exception_rm(devcgroup, &ex);
return 0;
}
@@ -533,10 +569,10 @@ struct cgroup_subsys devices_subsys = {
*
* returns 0 on success, -EPERM case the operation is not permitted
*/
-static int __devcgroup_check_permission(struct dev_cgroup *dev_cgroup,
- short type, u32 major, u32 minor,
+static int __devcgroup_check_permission(short type, u32 major, u32 minor,
short access)
{
+ struct dev_cgroup *dev_cgroup;
struct dev_exception_item ex;
int rc;
@@ -547,6 +583,7 @@ static int __devcgroup_check_permission(struct dev_cgroup *dev_cgroup,
ex.access = access;
rcu_read_lock();
+ dev_cgroup = task_devcgroup(current);
rc = may_access(dev_cgroup, &ex);
rcu_read_unlock();
@@ -558,7 +595,6 @@ static int __devcgroup_check_permission(struct dev_cgroup *dev_cgroup,
int __devcgroup_inode_permission(struct inode *inode, int mask)
{
- struct dev_cgroup *dev_cgroup = task_devcgroup(current);
short type, access = 0;
if (S_ISBLK(inode->i_mode))
@@ -570,13 +606,12 @@ int __devcgroup_inode_permission(struct inode *inode, int mask)
if (mask & MAY_READ)
access |= ACC_READ;
- return __devcgroup_check_permission(dev_cgroup, type, imajor(inode),
- iminor(inode), access);
+ return __devcgroup_check_permission(type, imajor(inode), iminor(inode),
+ access);
}
int devcgroup_inode_mknod(int mode, dev_t dev)
{
- struct dev_cgroup *dev_cgroup = task_devcgroup(current);
short type;
if (!S_ISBLK(mode) && !S_ISCHR(mode))
@@ -587,7 +622,7 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
else
type = DEV_CHAR;
- return __devcgroup_check_permission(dev_cgroup, type, MAJOR(dev),
- MINOR(dev), ACC_MKNOD);
+ return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev),
+ ACC_MKNOD);
}
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