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CRED: Use RCU to access another task's creds and to release a task's own creds

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Use RCU to access another task's creds and to release a task's own creds.
This means that it will be possible for the credentials of a task to be
replaced without another task (a) requiring a full lock to read them, and (b)
seeing deallocated memory.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
David Howells
2008-11-14 10:39:19 +11:00
committed by James Morris
parent 86a264abe5
commit c69e8d9c01
28 changed files with 353 additions and 202 deletions
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16
kernel/cgroup.c
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@@ -1279,7 +1279,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid)
{
struct task_struct *tsk;
uid_t euid;
const struct cred *cred = current_cred(), *tcred;
int ret;
if (pid) {
@@ -1289,16 +1289,16 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid)
rcu_read_unlock();
return -ESRCH;
}
get_task_struct(tsk);
rcu_read_unlock();
euid = current_euid();
if (euid &&
euid != tsk->cred->uid &&
euid != tsk->cred->suid) {
put_task_struct(tsk);
tcred = __task_cred(tsk);
if (cred->euid &&
cred->euid != tcred->uid &&
cred->euid != tcred->suid) {
rcu_read_unlock();
return -EACCES;
}
get_task_struct(tsk);
rcu_read_unlock();
} else {
tsk = current;
get_task_struct(tsk);