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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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30
arch/ia64/kernel/perfmon.c
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@@ -2399,25 +2399,33 @@ error_kmem:
static int
pfm_bad_permissions(struct task_struct *task)
{
const struct cred *tcred;
uid_t uid = current_uid();
gid_t gid = current_gid();
int ret;
rcu_read_lock();
tcred = __task_cred(task);
/* inspired by ptrace_attach() */
DPRINT(("cur: uid=%d gid=%d task: euid=%d suid=%d uid=%d egid=%d sgid=%d\n",
uid,
gid,
task->euid,
task->suid,
task->uid,
task->egid,
task->sgid));
tcred->euid,
tcred->suid,
tcred->uid,
tcred->egid,
tcred->sgid));
return (uid != task->euid)
|| (uid != task->suid)
|| (uid != task->uid)
|| (gid != task->egid)
|| (gid != task->sgid)
|| (gid != task->gid)) && !capable(CAP_SYS_PTRACE);
ret = ((uid != tcred->euid)
|| (uid != tcred->suid)
|| (uid != tcred->uid)
|| (gid != tcred->egid)
|| (gid != tcred->sgid)
|| (gid != tcred->gid)) && !capable(CAP_SYS_PTRACE);
rcu_read_unlock();
return ret;
}
static int