Commit 4cef7299 authored by Aristeu Rozanski's avatar Aristeu Rozanski Committed by Linus Torvalds
Browse files

device_cgroup: add proper checking when changing default behavior

Before changing a group's default behavior to ALLOW, we must check if
its parent's behavior is also ALLOW.
Signed-off-by: default avatarAristeu Rozanski <>
Cc: Tejun Heo <>
Cc: Li Zefan <>
Cc: James Morris <>
Cc: Pavel Emelyanov <>
Acked-by: default avatarSerge Hallyn <>
Cc: Jiri Slaby <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 26fd8405
......@@ -344,6 +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
......@@ -364,6 +375,8 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
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;
......@@ -375,9 +388,13 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
case 'a':
switch (filetype) {
if (!parent_has_perm(devcgroup, &ex))
if (!may_allow_all(parent))
return -EPERM;
rc = dev_exceptions_copy(&devcgroup->exceptions,
if (rc)
return rc;
devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
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