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Subject[PATCH] drm/vmwgfx: Check check that number of mip levels is above zero in vmw_surface_define_ioctl()
Date
In vmw_surface_define_ioctl(), a num_sizes parameter is assigned a
user-controlled value which is not checked for zero. It is used in
a call to kmalloc() which returns ZERO_SIZE_PTR. Later ZERO_SIZE_PTR
is dereferenced which leads to a GPF and possibly to a kernel panic.
Add the check for zero to avoid this.

Reference: https://bugzilla.redhat.com/show_bug.cgi?id=1435719
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
---
drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
index b445ce9..42840cc 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -716,8 +716,8 @@ int vmw_surface_define_ioctl(struct drm_device *dev, void *data,
for (i = 0; i < DRM_VMW_MAX_SURFACE_FACES; ++i)
num_sizes += req->mip_levels[i];

- if (num_sizes > DRM_VMW_MAX_SURFACE_FACES *
- DRM_VMW_MAX_MIP_LEVELS)
+ if (num_sizes <= 0 ||
+ num_sizes > DRM_VMW_MAX_SURFACE_FACES * DRM_VMW_MAX_MIP_LEVELS)
return -EINVAL;

size = vmw_user_surface_size + 128 +
--
2.9.3
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