drm/amdgpu: fix integer overflow in amdgpu_gem_align_pitch()

amdgpu_gem_align_pitch() is passed u32 width and cpp from dumb buffer
creation but uses signed int internally.  The round-up add and the
aligned * cpp multiplication can overflow, returning zero or a negative
pitch.  A zero pitch propagates to a zero-sized GEM object allocation
that reaches userspace via DRM_IOCTL_MODE_CREATE_DUMB.

Switch the helper to unsigned int and use check_add_overflow() /
check_mul_overflow() so wraparound returns zero.  Reject a zero pitch
or size in amdgpu_mode_dumb_create() rather than allocating a zero-
byte BO.

Fixes: 8e911ab770f7 ("drm: amdgpu: Replace drm_fb_get_bpp_depth() with drm_format_plane_cpp()")
Signed-off-by: Werner Kasselman <werner@verivus.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
index 5376035d32fe8e56b5497e53536e3c942fddc303..9ef80bca4102fd7529f02d0251d39dbc15f5294b 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
@@ -27,6 +27,7 @@
  */
 #include <linux/ktime.h>
 #include <linux/module.h>
+#include <linux/overflow.h>
 #include <linux/pagemap.h>
 #include <linux/pci.h>
 #include <linux/dma-buf.h>
@@ -1217,13 +1218,14 @@ int amdgpu_gem_list_handles_ioctl(struct drm_device *dev, void *data,
        return ret;
 }
 
-static int amdgpu_gem_align_pitch(struct amdgpu_device *adev,
-                                 int width,
-                                 int cpp,
-                                 bool tiled)
+static unsigned int amdgpu_gem_align_pitch(struct amdgpu_device *adev,
+                                          unsigned int width,
+                                          unsigned int cpp,
+                                          bool tiled)
 {
-       int aligned = width;
-       int pitch_mask = 0;
+       unsigned int aligned = width;
+       unsigned int pitch_mask = 0;
+       unsigned int pitch;
 
        switch (cpp) {
        case 1:
@@ -1238,9 +1240,12 @@ static int amdgpu_gem_align_pitch(struct amdgpu_device *adev,
                break;
        }
 
-       aligned += pitch_mask;
+       if (check_add_overflow(aligned, pitch_mask, &aligned))
+               return 0;
        aligned &= ~pitch_mask;
-       return aligned * cpp;
+       if (check_mul_overflow(aligned, cpp, &pitch))
+               return 0;
+       return pitch;
 }
 
 int amdgpu_mode_dumb_create(struct drm_file *file_priv,
@@ -1267,8 +1272,12 @@ int amdgpu_mode_dumb_create(struct drm_file *file_priv,
 
        args->pitch = amdgpu_gem_align_pitch(adev, args->width,
                                             DIV_ROUND_UP(args->bpp, 8), 0);
+       if (!args->pitch)
+               return -EINVAL;
        args->size = (u64)args->pitch * args->height;
        args->size = ALIGN(args->size, PAGE_SIZE);
+       if (!args->size)
+               return -EINVAL;
        domain = amdgpu_bo_get_preferred_domain(adev,
                                amdgpu_display_supported_domains(adev, flags));
        r = amdgpu_gem_object_create(adev, args->size, 0, domain, flags,