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authorDavid Howells <dhowells@redhat.com>2008-11-14 10:39:19 +1100
committerJames Morris <jmorris@namei.org>2008-11-14 10:39:19 +1100
commitc69e8d9c01db2adc503464993c358901c9af9de4 (patch)
treebed94aaa9aeb7a7834d1c880f72b62a11a752c78 /fs/ioprio.c
parent86a264abe542cfececb4df129bc45a0338d8cdb9 (diff)
downloadlinux-c69e8d9c01db2adc503464993c358901c9af9de4.tar.gz
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 'fs/ioprio.c')
-rw-r--r--fs/ioprio.c14
1 files changed, 10 insertions, 4 deletions
diff --git a/fs/ioprio.c b/fs/ioprio.c
index 5112554fd21..3569e0ad86a 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -31,10 +31,16 @@ static int set_task_ioprio(struct task_struct *task, int ioprio)
{
int err;
struct io_context *ioc;
+ const struct cred *cred = current_cred(), *tcred;
- if (task->cred->uid != current_euid() &&
- task->cred->uid != current_uid() && !capable(CAP_SYS_NICE))
+ rcu_read_lock();
+ tcred = __task_cred(task);
+ if (tcred->uid != cred->euid &&
+ tcred->uid != cred->uid && !capable(CAP_SYS_NICE)) {
+ rcu_read_unlock();
return -EPERM;
+ }
+ rcu_read_unlock();
err = security_task_setioprio(task, ioprio);
if (err)
@@ -131,7 +137,7 @@ asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
break;
do_each_thread(g, p) {
- if (p->cred->uid != who)
+ if (__task_cred(p)->uid != who)
continue;
ret = set_task_ioprio(p, ioprio);
if (ret)
@@ -224,7 +230,7 @@ asmlinkage long sys_ioprio_get(int which, int who)
break;
do_each_thread(g, p) {
- if (p->cred->uid != user->uid)
+ if (__task_cred(p)->uid != user->uid)
continue;
tmpio = get_task_ioprio(p);
if (tmpio < 0)