Patch "drm/vmwgfx: Fix possible null pointer derefence with invalid contexts" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    drm/vmwgfx: Fix possible null pointer derefence with invalid contexts

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-vmwgfx-fix-possible-null-pointer-derefence-with-.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 321032ef0d2e34caddb906632c46a1a57eeecb22
Author: Zack Rusin <zack.rusin@xxxxxxxxxxxx>
Date:   Wed Jan 10 15:03:05 2024 -0500

    drm/vmwgfx: Fix possible null pointer derefence with invalid contexts
    
    [ Upstream commit 517621b7060096e48e42f545fa6646fc00252eac ]
    
    vmw_context_cotable can return either an error or a null pointer and its
    usage sometimes went unchecked. Subsequent code would then try to access
    either a null pointer or an error value.
    
    The invalid dereferences were only possible with malformed userspace
    apps which never properly initialized the rendering contexts.
    
    Check the results of vmw_context_cotable to fix the invalid derefs.
    
    Thanks:
    ziming zhang(@ezrak1e) from Ant Group Light-Year Security Lab
    who was the first person to discover it.
    Niels De Graef who reported it and helped to track down the poc.
    
    Fixes: 9c079b8ce8bf ("drm/vmwgfx: Adapt execbuf to the new validation api")
    Cc: <stable@xxxxxxxxxxxxxxx> # v4.20+
    Reported-by: Niels De Graef  <ndegraef@xxxxxxxxxx>
    Signed-off-by: Zack Rusin <zack.rusin@xxxxxxxxxxxx>
    Cc: Martin Krastev <martin.krastev@xxxxxxxxxxxx>
    Cc: Maaz Mombasawala <maaz.mombasawala@xxxxxxxxxxxx>
    Cc: Ian Forbes <ian.forbes@xxxxxxxxxxxx>
    Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list@xxxxxxxxxxxx>
    Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
    Reviewed-by: Maaz Mombasawala <maaz.mombasawala@xxxxxxxxxxxx>
    Reviewed-by: Martin Krastev <martin.krastev@xxxxxxxxxxxx>
    Link: https://patchwork.freedesktop.org/patch/msgid/20240110200305.94086-1-zack.rusin@xxxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
index 36987ef3fc300..5fef0b31c1179 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -447,7 +447,7 @@ static int vmw_resource_context_res_add(struct vmw_private *dev_priv,
 	    vmw_res_type(ctx) == vmw_res_dx_context) {
 		for (i = 0; i < cotable_max; ++i) {
 			res = vmw_context_cotable(ctx, i);
-			if (IS_ERR(res))
+			if (IS_ERR_OR_NULL(res))
 				continue;
 
 			ret = vmw_execbuf_res_val_add(sw_context, res,
@@ -1266,6 +1266,8 @@ static int vmw_cmd_dx_define_query(struct vmw_private *dev_priv,
 		return -EINVAL;
 
 	cotable_res = vmw_context_cotable(ctx_node->ctx, SVGA_COTABLE_DXQUERY);
+	if (IS_ERR_OR_NULL(cotable_res))
+		return cotable_res ? PTR_ERR(cotable_res) : -EINVAL;
 	ret = vmw_cotable_notify(cotable_res, cmd->body.queryId);
 
 	return ret;
@@ -2484,6 +2486,8 @@ static int vmw_cmd_dx_view_define(struct vmw_private *dev_priv,
 		return ret;
 
 	res = vmw_context_cotable(ctx_node->ctx, vmw_view_cotables[view_type]);
+	if (IS_ERR_OR_NULL(res))
+		return res ? PTR_ERR(res) : -EINVAL;
 	ret = vmw_cotable_notify(res, cmd->defined_id);
 	if (unlikely(ret != 0))
 		return ret;
@@ -2569,8 +2573,8 @@ static int vmw_cmd_dx_so_define(struct vmw_private *dev_priv,
 
 	so_type = vmw_so_cmd_to_type(header->id);
 	res = vmw_context_cotable(ctx_node->ctx, vmw_so_cotables[so_type]);
-	if (IS_ERR(res))
-		return PTR_ERR(res);
+	if (IS_ERR_OR_NULL(res))
+		return res ? PTR_ERR(res) : -EINVAL;
 	cmd = container_of(header, typeof(*cmd), header);
 	ret = vmw_cotable_notify(res, cmd->defined_id);
 
@@ -2689,6 +2693,8 @@ static int vmw_cmd_dx_define_shader(struct vmw_private *dev_priv,
 		return -EINVAL;
 
 	res = vmw_context_cotable(ctx_node->ctx, SVGA_COTABLE_DXSHADER);
+	if (IS_ERR_OR_NULL(res))
+		return res ? PTR_ERR(res) : -EINVAL;
 	ret = vmw_cotable_notify(res, cmd->body.shaderId);
 	if (ret)
 		return ret;
@@ -3010,6 +3016,8 @@ static int vmw_cmd_dx_define_streamoutput(struct vmw_private *dev_priv,
 	}
 
 	res = vmw_context_cotable(ctx_node->ctx, SVGA_COTABLE_STREAMOUTPUT);
+	if (IS_ERR_OR_NULL(res))
+		return res ? PTR_ERR(res) : -EINVAL;
 	ret = vmw_cotable_notify(res, cmd->body.soid);
 	if (ret)
 		return ret;