diff options
| author | David Howells <dhowells@redhat.com> | 2008-11-14 10:39:19 +1100 |
|---|---|---|
| committer | James Morris <jmorris@namei.org> | 2008-11-14 10:39:19 +1100 |
| commit | c69e8d9c01db2adc503464993c358901c9af9de4 (patch) | |
| tree | bed94aaa9aeb7a7834d1c880f72b62a11a752c78 /mm/migrate.c | |
| parent | 86a264abe542cfececb4df129bc45a0338d8cdb9 (diff) | |
| download | lwn-c69e8d9c01db2adc503464993c358901c9af9de4.tar.gz lwn-c69e8d9c01db2adc503464993c358901c9af9de4.zip | |
CRED: Use RCU to access another task's creds and to release a task's own creds
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>
Diffstat (limited to 'mm/migrate.c')
| -rw-r--r-- | mm/migrate.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index 794443da1b4f..142284229ce2 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1045,7 +1045,7 @@ asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages, const int __user *nodes, int __user *status, int flags) { - struct cred *cred, *tcred; + const struct cred *cred = current_cred(), *tcred; struct task_struct *task; struct mm_struct *mm; int err; @@ -1076,14 +1076,16 @@ asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages, * capabilities, superuser privileges or the same * userid as the target process. */ - cred = current->cred; - tcred = task->cred; + rcu_read_lock(); + tcred = __task_cred(task); if (cred->euid != tcred->suid && cred->euid != tcred->uid && cred->uid != tcred->suid && cred->uid != tcred->uid && !capable(CAP_SYS_NICE)) { + rcu_read_unlock(); err = -EPERM; goto out; } + rcu_read_unlock(); err = security_task_movememory(task); if (err) |