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BUG: KASAN: use-after-free in v4l2_fh_init+0x279/0x2c0 drivers/media/v4l2-core/v4l2-fh.c:25
Read of size 8 at addr ffff88801eee08b8 by task v4l_id/9107

CPU: 1 PID: 9107 Comm: v4l_id Not tainted 5.12.0-rc4-next-20210326-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:232
 __kasan_report mm/kasan/report.c:399 [inline]
 kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:416
 v4l2_fh_init+0x279/0x2c0 drivers/media/v4l2-core/v4l2-fh.c:25
 v4l2_fh_open+0x88/0xc0 drivers/media/v4l2-core/v4l2-fh.c:63
 em28xx_v4l2_open+0x11c/0x570 drivers/media/usb/em28xx/em28xx-video.c:2163
 v4l2_open+0x21c/0x3f0 drivers/media/v4l2-core/v4l2-dev.c:429
 chrdev_open+0x266/0x770 fs/char_dev.c:414
 do_dentry_open+0x4b9/0x11b0 fs/open.c:826
 do_open fs/namei.c:3359 [inline]
 path_openat+0x1c0e/0x27e0 fs/namei.c:3492
 do_filp_open+0x17e/0x3c0 fs/namei.c:3519
 do_sys_openat2+0x16d/0x420 fs/open.c:1187
 do_sys_open fs/open.c:1203 [inline]
 __do_sys_open fs/open.c:1211 [inline]
 __se_sys_open fs/open.c:1207 [inline]
 __x64_sys_open+0x119/0x1c0 fs/open.c:1207
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f8597eb3840
Code: 73 01 c3 48 8b 0d 68 77 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 bb 20 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 1e f6 ff ff 48 89 04 24
RSP: 002b:00007ffc5a835b18 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007ffc5a835c88 RCX: 00007f8597eb3840
RDX: 00007f8597e9fea0 RSI: 0000000000000000 RDI: 00007ffc5a835f1f
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 000055cc51aa48d0
R13: 00007ffc5a835c80 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea00007bb800 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x1eee0
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0000900708 ffff88813fffb910 0000000000000000
raw: 0000000000000000 0000000000000002 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88801eee0780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88801eee0800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88801eee0880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                        ^
 ffff88801eee0900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88801eee0980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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