BUG: KASAN: vmalloc-out-of-bounds in memcpy include/linux/string.h:380 [inline]
BUG: KASAN: vmalloc-out-of-bounds in drm_fb_helper_dirty_blit_real drivers/gpu/drm/drm_fb_helper.c:399 [inline]
BUG: KASAN: vmalloc-out-of-bounds in drm_fb_helper_dirty_work+0x44c/0x780 drivers/gpu/drm/drm_fb_helper.c:428
Read of size 4096 at addr ffffc90008bc1000 by task kworker/1:3/17225

CPU: 1 PID: 17225 Comm: kworker/1:3 Not tainted 5.5.0-rc2-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+0x197/0x210 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0x5/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:639
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
 memcpy+0x24/0x50 mm/kasan/common.c:125
 memcpy include/linux/string.h:380 [inline]
 drm_fb_helper_dirty_blit_real drivers/gpu/drm/drm_fb_helper.c:399 [inline]
 drm_fb_helper_dirty_work+0x44c/0x780 drivers/gpu/drm/drm_fb_helper.c:428
 process_one_work+0x9af/0x1740 kernel/workqueue.c:2264
 worker_thread+0x98/0xe40 kernel/workqueue.c:2410
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352


Memory state around the buggy address:
 ffffc90008bc0f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90008bc0f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90008bc1000: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
                   ^
 ffffc90008bc1080: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
 ffffc90008bc1100: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
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