iosys-map: Fix undefined behavior in iosys_map_clear()

The current iosys_map_clear() implementation reads the potentially
uninitialized 'is_iomem' boolean field to decide which union member
to clear. This causes undefined behavior when called on uninitialized
structures, as 'is_iomem' may contain garbage values like 0xFF.

UBSAN detects this as:
    UBSAN: invalid-load in include/linux/iosys-map.h:267
    load of value 255 is not a valid value for type '_Bool'

Fix by unconditionally clearing the entire structure with memset(),
eliminating the need to read uninitialized data and ensuring all
fields are set to known good values.

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14639
Fixes: 01fd30da0474 ("dma-buf: Add struct dma-buf-map for storing struct dma_buf.vaddr_ptr")
Signed-off-by: Nitin Gote <nitin.r.gote@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20250718105051.2709487-1-nitin.r.gote@intel.com

diff --git a/include/linux/iosys-map.h b/include/linux/iosys-map.h
index 4696abfd311cc16614762bdec10d4ef461c62e72..3e85afe794c0aa0c65876aa47761b3cf50ca8273 100644 (file)
--- a/include/linux/iosys-map.h
+++ b/include/linux/iosys-map.h
@@ -264,12 +264,7 @@ static inline bool iosys_map_is_set(const struct iosys_map *map)
  */
 static inline void iosys_map_clear(struct iosys_map *map)
 {
-       if (map->is_iomem) {
-               map->vaddr_iomem = NULL;
-               map->is_iomem = false;
-       } else {
-               map->vaddr = NULL;
-       }
+       memset(map, 0, sizeof(*map));
 }
 
 /**