[BUG] vga16fb_probe -- KASAN slab-out-of-bounds reading platform_data

[Farhad Alemi]

Hello,

As part of the kernel research at ASU's SEFCOM
lab, we hit the crash below. Crash reports can be found here:

  https://github.com/farhad-alemi/public_bug_reports/tree/main/151-fbdev-vga16fb-vesafb-efifb-platdata-size-check/

  BUG: KASAN: slab-out-of-bounds in vga16fb_probe+0x828/0x9e0
  Read of size 1 at addr ffff888105ba2dcf by task repro/9494
  Call Trace:
   vga16fb_probe+0x828/0x9e0
   platform_probe+0xf9/0x190
   really_probe+0x267/0xaf0
   __driver_probe_device+0x1e2/0x350
   device_driver_attach+0xe0/0x1d0
   bind_store+0x1d0/0x220
   kernfs_fop_write_iter+0x3af/0x540
   vfs_write+0x61d/0xb90
   ksys_write+0x150/0x270

Our reproducer.c is available upon request.

Happy to test a patch if that would help.

Regards,