Re: [PATCH] fbdev: core: Fix vmalloc-out-of-bounds in fb_imageblit

[kernel test robot]

Hi,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on drm-tip/drm-tip linus/master v6.18-rc6 next-20251119]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/ssrane_b23-ee-vjti-ac-in/fbdev-core-Fix-vmalloc-out-of-bounds-in-fb_imageblit/20251119-215054
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20251119133821.89998-1-ssranevjti%40gmail.com
patch subject: [PATCH] fbdev: core: Fix vmalloc-out-of-bounds in fb_imageblit
config: nios2-randconfig-r073-20251120 (https://download.01.org/0day-ci/archive/20251120/202511201752.4fVbQwPc-lkp@xxxxxxxxx/config)
compiler: nios2-linux-gcc (GCC) 10.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251120/202511201752.4fVbQwPc-lkp@xxxxxxxxx/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511201752.4fVbQwPc-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

   In file included from drivers/video/fbdev/core/cfbimgblt.c:17:
   drivers/video/fbdev/core/fb_imageblit.h: In function 'fb_imageblit':
>> drivers/video/fbdev/core/fb_imageblit.h:490:16: warning: unused variable 'max_offset_bytes' [-Wunused-variable]
     490 |  unsigned long max_offset_bytes;
         |                ^~~~~~~~~~~~~~~~


vim +/max_offset_bytes +490 drivers/video/fbdev/core/fb_imageblit.h

   480	
   481	static inline void fb_imageblit(struct fb_info *p, const struct fb_image *image)
   482	{
   483		int bpp = p->var.bits_per_pixel;
   484		unsigned int bits_per_line = BYTES_TO_BITS(p->fix.line_length);
   485		struct fb_address dst = fb_address_init(p);
   486		struct fb_reverse reverse = fb_reverse_init(p);
   487		const u32 *palette = fb_palette(p);
   488		struct fb_image clipped_image;
   489		u32 max_x, max_y;
 > 490		unsigned long max_offset_bytes;

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