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Subject[PATCH 4/6] file capabilities: clean up setcap code
Date
Clean up the sys_capset codepath a bit to account for the fact
that you can now not ever, never, capset on another task.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
---
kernel/capability.c | 83 +++++++++++++++++++-------------------------------
1 files changed, 32 insertions(+), 51 deletions(-)
diff --git a/kernel/capability.c b/kernel/capability.c
index d39c989..92dd85b 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -132,46 +132,31 @@ static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
* process. The net result is that we can limit our use of locks to
* when we are reading the caps of another process.
*/
-static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
+static int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
kernel_cap_t *pIp, kernel_cap_t *pPp)
{
int ret;
+ struct task_struct *target;

- if (pid && (pid != task_pid_vnr(current))) {
- struct task_struct *target;
+ if (!pid || pid == task_pid_vnr(current))
+ return security_capget(current, pEp, pIp, pPp);

- spin_lock(&task_capability_lock);
- read_lock(&tasklist_lock);
+ spin_lock(&task_capability_lock);
+ read_lock(&tasklist_lock);

- target = find_task_by_vpid(pid);
- if (!target)
- ret = -ESRCH;
- else
- ret = security_capget(target, pEp, pIp, pPp);
+ target = find_task_by_vpid(pid);
+ if (!target)
+ ret = -ESRCH;
+ else
+ ret = security_capget(target, pEp, pIp, pPp);

- read_unlock(&tasklist_lock);
- spin_unlock(&task_capability_lock);
- } else
- ret = security_capget(current, pEp, pIp, pPp);
+ read_unlock(&tasklist_lock);
+ spin_unlock(&task_capability_lock);

return ret;
}

/*
- * With filesystem capability support configured, the kernel does not
- * permit the changing of capabilities in one process by another
- * process. (CAP_SETPCAP has much less broad semantics when configured
- * this way.)
- */
-static inline int do_sys_capset_other_tasks(pid_t pid,
- kernel_cap_t *effective,
- kernel_cap_t *inheritable,
- kernel_cap_t *permitted)
-{
- return -EPERM;
-}
-
-/*
* Atomically modify the effective capabilities returning the original
* value. No permission check is performed here - it is assumed that the
* caller is permitted to set the desired effective capabilities.
@@ -293,6 +278,9 @@ asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
if (get_user(pid, &header->pid))
return -EFAULT;

+ if (pid && (pid != task_pid_vnr(current)))
+ return -EPERM;
+
if (copy_from_user(&kdata, data, tocopy
* sizeof(struct __user_cap_data_struct))) {
return -EFAULT;
@@ -310,30 +298,23 @@ asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
i++;
}

- if (pid && (pid != task_pid_vnr(current)))
- ret = do_sys_capset_other_tasks(pid, &effective, &inheritable,
- &permitted);
- else {
- /*
- * This lock is required even when filesystem
- * capability support is configured - it protects the
- * sys_capget() call from returning incorrect data in
- * the case that the targeted process is not the
- * current one.
- */
- spin_lock(&task_capability_lock);
+ /*
+ * This lock protects the sys_capget() call from
+ * returning incorrect data in the case that the targeted
+ * process is not the current one.
+ */
+ spin_lock(&task_capability_lock);

- ret = security_capset_check(current, &effective, &inheritable,
- &permitted);
- /*
- * Having verified that the proposed changes are
- * legal, we now put them into effect.
- */
- if (!ret)
- security_capset_set(current, &effective, &inheritable,
- &permitted);
- spin_unlock(&task_capability_lock);
- }
+ ret = security_capset_check(current, &effective, &inheritable,
+ &permitted);
+ /*
+ * Having verified that the proposed changes are
+ * legal, we now put them into effect.
+ */
+ if (!ret)
+ security_capset_set(current, &effective, &inheritable,
+ &permitted);
+ spin_unlock(&task_capability_lock);


return ret;
--
1.5.1.1.GIT


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