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>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 6862b36..cf42c42 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1406,6 +1406,7 @@
{
struct inode * inode;
struct proc_inode *ei;
+ const struct cred *cred;
/* We need a new inode */
@@ -1428,8 +1429,11 @@
inode->i_uid = 0;
inode->i_gid = 0;
if (task_dumpable(task)) {
- inode->i_uid = task->cred->euid;
- inode->i_gid = task->cred->egid;
+ rcu_read_lock();
+ cred = __task_cred(task);
+ inode->i_uid = cred->euid;
+ inode->i_gid = cred->egid;
+ rcu_read_unlock();
}
security_task_to_inode(task, inode);
@@ -1445,6 +1449,8 @@
{
struct inode *inode = dentry->d_inode;
struct task_struct *task;
+ const struct cred *cred;
+
generic_fillattr(inode, stat);
rcu_read_lock();
@@ -1454,8 +1460,9 @@
if (task) {
if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||
task_dumpable(task)) {
- stat->uid = task->cred->euid;
- stat->gid = task->cred->egid;
+ cred = __task_cred(task);
+ stat->uid = cred->euid;
+ stat->gid = cred->egid;
}
}
rcu_read_unlock();
@@ -1483,11 +1490,16 @@
{
struct inode *inode = dentry->d_inode;
struct task_struct *task = get_proc_task(inode);
+ const struct cred *cred;
+
if (task) {
if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||
task_dumpable(task)) {
- inode->i_uid = task->cred->euid;
- inode->i_gid = task->cred->egid;
+ rcu_read_lock();
+ cred = __task_cred(task);
+ inode->i_uid = cred->euid;
+ inode->i_gid = cred->egid;
+ rcu_read_unlock();
} else {
inode->i_uid = 0;
inode->i_gid = 0;
@@ -1649,6 +1661,7 @@
struct task_struct *task = get_proc_task(inode);
int fd = proc_fd(inode);
struct files_struct *files;
+ const struct cred *cred;
if (task) {
files = get_files_struct(task);
@@ -1658,8 +1671,11 @@
rcu_read_unlock();
put_files_struct(files);
if (task_dumpable(task)) {
- inode->i_uid = task->cred->euid;
- inode->i_gid = task->cred->egid;
+ rcu_read_lock();
+ cred = __task_cred(task);
+ inode->i_uid = cred->euid;
+ inode->i_gid = cred->egid;
+ rcu_read_unlock();
} else {
inode->i_uid = 0;
inode->i_gid = 0;