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drm/hyperv: validate resolution_count and fix WIN8 fallback

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A SYNTHVID_RESOLUTION_RESPONSE with resolution_count > 64 walks past
the supported_resolution[SYNTHVID_MAX_RESOLUTION_COUNT] array in the
parse loop. Bound resolution_count against the array size, folded
into the existing zero-check.

When the WIN10 resolution probe fails, the caller in
hyperv_connect_vsp() left hv->screen_*_max / preferred_* unpopulated,
which sets mode_config.max_width / max_height to 0 and makes
drm_internal_framebuffer_create() reject every userspace framebuffer
with -EINVAL. The pre-WIN10 branch had the same gap for
preferred_width / preferred_height. Use a single post-probe fallback
guarded by screen_width_max == 0 so both paths converge on the WIN8
defaults.

Signed-off-by: Berkant Koc <me@berkoc.com>
Assisted-by: Claude:claude-opus-4-7 berkoc-pipeline
Fixes: 76c56a5aff ("drm/hyperv: Add DRM driver for hyperv synthetic video device")
Cc: stable@vger.kernel.org # 5.14+
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
Link: https://patch.msgid.link/6945b22419c7d404b4954a113de2ac9c900dba93.1779542874.git.me@berkoc.com
This commit is contained in:
Berkant Koc 2026-05-19 22:08:17 +02:00 committed by Hamza Mahfooz
parent a8878e19d2
commit 13d33b9ef6
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GPG Key ID: 3D6797D6EE6FCAE2
1 changed files with 10 additions and 3 deletions
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13
drivers/gpu/drm/hyperv/hyperv_drm_proto.c
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@ -391,8 +391,11 @@ static int hyperv_get_supported_resolution(struct hv_device *hdev)
return -ETIMEDOUT;
}
if (msg->resolution_resp.resolution_count == 0) {
drm_err(dev, "No supported resolutions\n");
if (msg->resolution_resp.resolution_count == 0 ||
msg->resolution_resp.resolution_count >
SYNTHVID_MAX_RESOLUTION_COUNT) {
drm_err(dev, "Invalid resolution count: %d\n",
msg->resolution_resp.resolution_count);
return -ENODEV;
}
@ -508,9 +511,13 @@ int hyperv_connect_vsp(struct hv_device *hdev)
ret = hyperv_get_supported_resolution(hdev);
if (ret)
drm_err(dev, "Failed to get supported resolution from host, use default\n");
} else {
}
if (!hv->screen_width_max) {
hv->screen_width_max = SYNTHVID_WIDTH_WIN8;
hv->screen_height_max = SYNTHVID_HEIGHT_WIN8;
hv->preferred_width = SYNTHVID_WIDTH_WIN8;
hv->preferred_height = SYNTHVID_HEIGHT_WIN8;
}
hv->mmio_megabytes = hdev->channel->offermsg.offer.mmio_megabytes;