1 files changed, 23 insertions, 6 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 100a71cfdaba..29dc700e198c 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -127,6 +127,8 @@ int ptrace_check_attach(struct task_struct *child, int kill)
 
 int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 {
+        const struct cred *cred = current_cred(), *tcred;
+
         /* May we inspect the given task?
          * This check is used both for attaching with ptrace
          * and for allowing access to sensitive information in /proc.
@@ -139,13 +141,19 @@ int __ptrace_may_access(struct task_struct *task, unsigned int mode)
         /* Don't let security modules deny introspection */
         if (task == current)
                 return 0;
-        if (((current->uid != task->euid) ||
-             (current->uid != task->suid) ||
-             (current->uid != task->uid) ||
-             (current->gid != task->egid) ||
-             (current->gid != task->sgid) ||
-             (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
+        rcu_read_lock();
+        tcred = __task_cred(task);
+        if ((cred->uid != tcred->euid ||
+             cred->uid != tcred->suid ||
+             cred->uid != tcred->uid  ||
+             cred->gid != tcred->egid ||
+             cred->gid != tcred->sgid ||
+             cred->gid != tcred->gid) &&
+            !capable(CAP_SYS_PTRACE)) {
+                rcu_read_unlock();
                 return -EPERM;
+        }
+        rcu_read_unlock();
         smp_rmb();
         if (task->mm)
                 dumpable = get_dumpable(task->mm);
@@ -175,6 +183,14 @@ int ptrace_attach(struct task_struct *task)
         if (same_thread_group(task, current))
                 goto out;
 
+        /* Protect exec's credential calculations against our interference;
+         * SUID, SGID and LSM creds get determined differently under ptrace.
+         */
+        retval = mutex_lock_interruptible(&current->cred_exec_mutex);
+        if (retval  < 0)
+                goto out;
+
+        retval = -EPERM;
 repeat:
         /*
          * Nasty, nasty.
@@ -214,6 +230,7 @@ repeat:
 bad:
         write_unlock_irqrestore(&tasklist_lock, flags);
         task_unlock(task);
+        mutex_unlock(&current->cred_exec_mutex);
 out:
         return retval;
 }