[PATCH 22/43] userns: Convert capabilities related permsion checks

"Eric W. Beiderman
2012-04-08T05:13:05Z

From: Eric W. Biederman <ebiederm@xmission.com>

- Use uid_eq when comparing kuids
Use gid_eq when comparing kgids
- Use __make_kuid(user_ns, 0) to talk about the user_namespace root uid
Use __make_kgid(user_ns, 0) to talk about the user_namespace root gid

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
fs/open.c | 3 ++-
security/commoncap.c | 43 ++++++++++++++++++++++++++++---------------
2 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 5720854..92335f6 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -316,7 +316,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)

if (!issecure(SECURE_NO_SETUID_FIXUP)) {
/* Clear the capabilities if we switch to a non-root user */
- if (override_cred->uid)
+ kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
+ if (!uid_eq(override_cred->uid, root_uid))
cap_clear(override_cred->cap_effective);
else
override_cred->cap_effective =
diff --git a/security/commoncap.c b/security/commoncap.c
index dbd465a..9bf8df8 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -472,19 +472,24 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
struct cred *new = bprm->cred;
bool effective, has_cap = false;
int ret;
+ kuid_t root_uid;
+ kgid_t root_gid;

effective = false;
ret = get_file_caps(bprm, &effective, &has_cap);
if (ret < 0)
return ret;

+ root_uid = make_kuid(new->user_ns, 0);
+ root_gid = make_kgid(new->user_ns, 0);
+
if (!issecure(SECURE_NOROOT)) {
/*
* If the legacy file capability is set, then don't set privs
* for a setuid root binary run by a non-root user. Do set it
* for a root user just to cause least surprise to an admin.
*/
- if (has_cap && new->uid != 0 && new->euid == 0) {
+ if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
warn_setuid_and_fcaps_mixed(bprm->filename);
goto skip;
}
@@ -495,12 +500,12 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
*
* If only the real uid is 0, we do not set the effective bit.
*/
- if (new->euid == 0 || new->uid == 0) {
+ if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
/* pP' = (cap_bset & ~0) | (pI & ~0) */
new->cap_permitted = cap_combine(old->cap_bset,
old->cap_inheritable);
}
- if (new->euid == 0)
+ if (uid_eq(new->euid, root_uid))
effective = true;
}
skip:
@@ -508,8 +513,8 @@ skip:
/* Don't let someone trace a set[ug]id/setpcap binary with the revised
* credentials unless they have the appropriate permit
*/
- if ((new->euid != old->uid ||
- new->egid != old->gid ||
+ if ((!uid_eq(new->euid, old->uid) ||
+ !gid_eq(new->egid, old->gid) ||
!cap_issubset(new->cap_permitted, old->cap_permitted)) &&
bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
/* downgrade; they get no more than they had, and maybe less */
@@ -544,7 +549,7 @@ skip:
*/
if (!cap_isclear(new->cap_effective)) {
if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
- new->euid != 0 || new->uid != 0 ||
+ !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
issecure(SECURE_NOROOT)) {
ret = audit_log_bprm_fcaps(bprm, new, old);
if (ret < 0)
@@ -569,16 +574,17 @@ skip:
int cap_bprm_secureexec(struct linux_binprm *bprm)
{
const struct cred *cred = current_cred();
+ kuid_t root_uid = make_kuid(cred->user_ns, 0);

- if (cred->uid != 0) {
+ if (!uid_eq(cred->uid, root_uid)) {
if (bprm->cap_effective)
return 1;
if (!cap_isclear(cred->cap_permitted))
return 1;
}

- return (cred->euid != cred->uid ||
- cred->egid != cred->gid);
+ return (!uid_eq(cred->euid, cred->uid) ||
+ !gid_eq(cred->egid, cred->gid));
}

/**
@@ -668,15 +674,21 @@ int cap_inode_removexattr(struct dentry *dentry, const char *name)
*/
static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
{
- if ((old->uid == 0 || old->euid == 0 || old->suid == 0) &&
- (new->uid != 0 && new->euid != 0 && new->suid != 0) &&
+ kuid_t root_uid = make_kuid(old->user_ns, 0);
+
+ if ((uid_eq(old->uid, root_uid) ||
+ uid_eq(old->euid, root_uid) ||
+ uid_eq(old->suid, root_uid)) &&
+ (!uid_eq(new->uid, root_uid) &&
+ !uid_eq(new->euid, root_uid) &&
+ !uid_eq(new->suid, root_uid)) &&
!issecure(SECURE_KEEP_CAPS)) {
cap_clear(new->cap_permitted);
cap_clear(new->cap_effective);
}
- if (old->euid == 0 && new->euid != 0)
+ if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
cap_clear(new->cap_effective);
- if (old->euid != 0 && new->euid == 0)
+ if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
new->cap_effective = new->cap_permitted;
}

@@ -709,11 +721,12 @@ int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
* if not, we might be a bit too harsh here.
*/
if (!issecure(SECURE_NO_SETUID_FIXUP)) {
- if (old->fsuid == 0 && new->fsuid != 0)
+ kuid_t root_uid = make_kuid(old->user_ns, 0);
+ if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
new->cap_effective =
cap_drop_fs_set(new->cap_effective);

- if (old->fsuid != 0 && new->fsuid == 0)
+ if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
new->cap_effective =
cap_raise_fs_set(new->cap_effective,
new->cap_permitted);
--
1.7.2.5