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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
Write of size 4096 at addr ffffc90009bd1000 by task kworker/2:0/23

CPU: 2 PID: 23 Comm: kworker/2:0 Not tainted 5.10.0-rc1-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+0x39/0x60 mm/kasan/common.c:106
 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+0x3af/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296


Memory state around the buggy address:
 ffffc90009bd0f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90009bd0f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90009bd1000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                   ^
 ffffc90009bd1080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90009bd1100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
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