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-rw-r--r--fs/proc/base.c26
1 files changed, 22 insertions, 4 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 9af49a3..013f116 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -191,10 +191,7 @@ static int proc_root_link(struct inode *inode, struct path *path)
return result;
}
-/*
- * Return zero if current may access user memory in @task, -error if not.
- */
-static int check_mem_permission(struct task_struct *task)
+static int __check_mem_permission(struct task_struct *task)
{
/*
* A task can always look at itself, in case it chooses
@@ -222,6 +219,27 @@ static int check_mem_permission(struct task_struct *task)
return -EPERM;
}
+/*
+ * Return zero if current may access user memory in @task, -error if not.
+ */
+static int check_mem_permission(struct task_struct *task)
+{
+ int err;
+
+ /*
+ * Avoid racing if task exec's as we might get a new mm but validate
+ * against old credentials.
+ */
+ err = mutex_lock_killable(&task->signal->cred_guard_mutex);
+ if (err)
+ return err;
+
+ err = __check_mem_permission(task);
+ mutex_unlock(&task->signal->cred_guard_mutex);
+
+ return err;
+}
+
struct mm_struct *mm_for_maps(struct task_struct *task)
{
struct mm_struct *mm;
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