linux-kernel - [PATCH 5.15 179/846] drm/vmwgfx: Fail to initialize on broken configs

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Date:   Mon, 24 Jan 2022 19:34:56 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Zack Rusin <zackr@...are.com>,
        Martin Krastev <krastevm@...are.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 179/846] drm/vmwgfx: Fail to initialize on broken configs

From: Zack Rusin <zackr@...are.com>

[ Upstream commit c451af78f301ff5156998d571c37cab329c10051 ]

Some of our hosts have a bug where rescaning a pci bus results in stale
fifo memory being mapped on the host. This makes any fifo communication
impossible resulting in various kernel crashes.

Instead of unexpectedly crashing, predictably fail to load the driver
which will preserve the system.

Fixes: fb1d9738ca05 ("drm/vmwgfx: Add DRM driver for VMware Virtual GPU")
Signed-off-by: Zack Rusin <zackr@...are.com>
Reviewed-by: Martin Krastev <krastevm@...are.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211105193845.258816-4-zackr@vmware.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_cmd.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_cmd.c b/drivers/gpu/drm/vmwgfx/vmwgfx_cmd.c
index 67db472d3493c..a3bfbb6c3e14a 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_cmd.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_cmd.c
@@ -145,6 +145,13 @@ struct vmw_fifo_state *vmw_fifo_create(struct vmw_private *dev_priv)
 		 (unsigned int) max,
 		 (unsigned int) min,
 		 (unsigned int) fifo->capabilities);
+
+	if (unlikely(min >= max)) {
+		drm_warn(&dev_priv->drm,
+			 "FIFO memory is not usable. Driver failed to initialize.");
+		return ERR_PTR(-ENXIO);
+	}
+
 	return fifo;
 }
 
-- 
2.34.1