[PATCH] drm/amdkfd: stop speculation on the kfd_ioctl path

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

The kfd_ioctl takes a user controlled pointer, and then dereferences it
into a table of function pointers, the signature method of spectre
problems.  Fix this up by calling array_index_nospec() on the index to
the function pointer list.

Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: stable <stable@kernel.org>
Assisted-by: gkh_clanker_2000
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
index 09dabb3b3297..d2ef693c63da 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
@@ -35,6 +35,7 @@
 #include <linux/mman.h>
 #include <linux/ptrace.h>
 #include <linux/dma-buf.h>
+#include <linux/nospec.h>
 #include <linux/processor.h>
 #include "kfd_priv.h"
 #include "kfd_device_queue_manager.h"
@@ -3349,6 +3350,7 @@ static long kfd_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
 	if ((nr >= AMDKFD_COMMAND_START) && (nr < AMDKFD_COMMAND_END)) {
 		u32 amdkfd_size;
 
+		nr = array_index_nospec(nr, AMDKFD_CORE_IOCTL_COUNT);
 		ioctl = &amdkfd_ioctls[nr];
 
 		amdkfd_size = _IOC_SIZE(ioctl->cmd);
-- 
2.53.0