From 46df5a4cda4c703d075b980359d0bac2a3cd9fc5 Mon Sep 17 00:00:00 2001
From: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Date: Mon, 23 Oct 2017 17:34:52 -0400
Subject: [PATCH 2036/4131] drm/amdkfd: Relaxed mm_access for CMA

mm_access() is not exported. So for DKMS build implement a relaxed
version of mm_access. This will be enabled only when module param
amdkfd.cma_enable is set.

BUG:SWDEV-136049

Change-Id: I4bbab6e74da1c8db465e33bb44f9cc9bc2df6f3a
Signed-off-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 61 +++++++++++++++++++++++++++++---
 drivers/gpu/drm/amd/amdkfd/kfd_module.c  |  5 +++
 drivers/gpu/drm/amd/amdkfd/kfd_priv.h    |  6 ++++
 3 files changed, 67 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
index b2795af..75a9a45 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
@@ -1681,12 +1681,58 @@ static int kfd_ioctl_get_tile_config(struct file *filep,
 }
 
 #if defined(BUILD_AS_DKMS)
-static int kfd_ioctl_cross_memory_copy(struct file *filep,
-				       struct kfd_process *local_p, void *data)
+static bool kfd_may_access(struct task_struct *task, unsigned int mode)
 {
-	return 0;
+	bool access = false;
+	const struct cred *cred = current_cred(), *tcred;
+	kuid_t caller_uid = cred->fsuid;
+	kgid_t caller_gid = cred->fsgid;
+
+	task_lock(task);
+
+	if (same_thread_group(task, current)) {
+		access = true;
+		goto ok;
+	}
+
+	tcred = __task_cred(task);
+	if (uid_eq(caller_uid, tcred->euid) &&
+	    uid_eq(caller_uid, tcred->suid) &&
+	    uid_eq(caller_uid, tcred->uid)  &&
+	    gid_eq(caller_gid, tcred->egid) &&
+	    gid_eq(caller_gid, tcred->sgid) &&
+	    gid_eq(caller_gid, tcred->gid))
+		access = true;
+
+ok:
+	task_unlock(task);
+	return access;
 }
-#else
+/* mm_access() is currently not exported. This is a relaxed implementation
+ * that allows access as long as both process belong to same uid
+ */
+static struct mm_struct *kfd_relaxed_mm_access(struct task_struct *task,
+					       unsigned int mode)
+{
+	struct mm_struct *mm;
+	int err;
+
+	err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
+	if (err)
+		return ERR_PTR(err);
+
+	mm = get_task_mm(task);
+	if (mm && mm != current->mm &&
+			!kfd_may_access(task, mode)) {
+		mmput(mm);
+		mm = ERR_PTR(-EACCES);
+	}
+	mutex_unlock(&task->signal->cred_guard_mutex);
+
+	return mm;
+}
+#endif
+
 static int kfd_ioctl_cross_memory_copy(struct file *filep,
 				       struct kfd_process *local_p, void *data)
 {
@@ -1748,7 +1794,13 @@ static int kfd_ioctl_cross_memory_copy(struct file *filep,
 	}
 
 	/* Check access permission */
+#if defined(BUILD_AS_DKMS)
+	remote_mm = cma_enable ? kfd_relaxed_mm_access(remote_task,
+				PTRACE_MODE_ATTACH_REALCREDS) :
+				ERR_PTR(-EACCES);
+#else
 	remote_mm = mm_access(remote_task, PTRACE_MODE_ATTACH_REALCREDS);
+#endif
 	if (!remote_mm || IS_ERR(remote_mm)) {
 		err = IS_ERR(remote_mm) ? PTR_ERR(remote_mm) : -ESRCH;
 		if (err == -EACCES) {
@@ -1928,7 +1980,6 @@ static int kfd_ioctl_cross_memory_copy(struct file *filep,
 	args->bytes_copied = total_copied;
 	return err;
 }
-#endif
 
 static int kfd_ioctl_get_queue_wave_state(struct file *filep,
 					  struct kfd_process *p, void *data)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_module.c b/drivers/gpu/drm/amd/amdkfd/kfd_module.c
index aba3e9d..36da8c4 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_module.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_module.c
@@ -89,6 +89,11 @@ module_param_named(noretry, vega10_noretry, int, 0644);
 MODULE_PARM_DESC(noretry,
 	"Set sh_mem_config.retry_disable on Vega10 (0 = retry enabled (default), 1 = retry disabled)");
 
+int cma_enable;
+module_param(cma_enable, int, 0644);
+MODULE_PARM_DESC(cma_enable,
+	"Enable CMA (1 = enable, 0 = disable (default)). Warning! relaxed access check");
+
 int kgd2kfd_init(unsigned int interface_version,
 		const struct kgd2kfd_calls **g2f)
 {
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
index cceaa89..1de2d91 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
@@ -139,6 +139,12 @@ extern int ignore_crat;
  */
 extern int vega10_noretry;
 
+/*
+ * Currently, mm_access() function is not exported. So for DKMS build,
+ * CMA will be enabled only if module param is set.
+ */
+extern int cma_enable;
+
 /**
  * enum kfd_sched_policy
  *
-- 
2.7.4