KASAN: vmalloc-out-of-bounds Read in drm_fb_helper_dirty_work (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    a2f5ea9e Merge tag 'arm-soc-fixes-v5.10-4b' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=167b497b500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=868cd1c95c02180
dashboard link: https://syzkaller.appspot.com/bug?extid=cc9acdabdf6ea0c8dc0b
compiler:       gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cc9acdabdf6ea0c8dc0b at syzkaller.appspotmail.com

==================================================================
BUG: KASAN: vmalloc-out-of-bounds in memcpy include/linux/string.h:399 [inline]
BUG: KASAN: vmalloc-out-of-bounds in drm_fb_helper_dirty_blit_real drivers/gpu/drm/drm_fb_helper.c:403 [inline]
BUG: KASAN: vmalloc-out-of-bounds in drm_fb_helper_dirty_work+0x42e/0x810 drivers/gpu/drm/drm_fb_helper.c:435
Read of size 3168 at addr ffffc9000b8613a0 by task kworker/0:5/11875

CPU: 0 PID: 11875 Comm: kworker/0:5 Not tainted 5.10.0-rc7-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Workqueue: events drm_fb_helper_dirty_work
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0x5/0x497 mm/kasan/report.c:385
 __kasan_report mm/kasan/report.c:545 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
 check_memory_region_inline mm/kasan/generic.c:186 [inline]
 check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
 memcpy+0x20/0x60 mm/kasan/common.c:105
 memcpy include/linux/string.h:399 [inline]
 drm_fb_helper_dirty_blit_real drivers/gpu/drm/drm_fb_helper.c:403 [inline]
 drm_fb_helper_dirty_work+0x42e/0x810 drivers/gpu/drm/drm_fb_helper.c:435
 process_one_work+0x933/0x15a0 kernel/workqueue.c:2272
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2418
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296


Memory state around the buggy address:
 ffffc9000b861280: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc9000b861300: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc9000b861380: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                               ^
 ffffc9000b861400: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc9000b861480: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================


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