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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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15
fs/fcntl.c
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@ -401,10 +401,17 @@ static const long band_table[NSIGPOLL] = {
static inline int sigio_perm(struct task_struct *p,
struct fown_struct *fown, int sig)
{
return (((fown->euid == 0) ||
(fown->euid == p->cred->suid) || (fown->euid == p->cred->uid) ||
(fown->uid == p->cred->suid) || (fown->uid == p->cred->uid)) &&
!security_file_send_sigiotask(p, fown, sig));
const struct cred *cred;
int ret;
rcu_read_lock();
cred = __task_cred(p);
ret = ((fown->euid == 0 ||
fown->euid == cred->suid || fown->euid == cred->uid ||
fown->uid == cred->suid || fown->uid == cred->uid) &&
!security_file_send_sigiotask(p, fown, sig));
rcu_read_unlock();
return ret;
}
static void send_sigio_to_task(struct task_struct *p,