KASAN: out-of-bounds Read in v4l2_fh_init

[syzbot <syzbot+431a2669cfb42d234b9c@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    93578a25 usb: musb: gadget: Use fallthrough pseudo-keyword
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=1480f19f900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=df3bb4023c36d114
dashboard link: https://syzkaller.appspot.com/bug?extid=431a2669cfb42d234b9c
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+431a2669cfb42d234b9c@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: out-of-bounds in v4l2_fh_init+0x279/0x2c0 drivers/media/v4l2-core/v4l2-fh.c:25
Read of size 8 at addr ffff8881c72788c0 by task v4l_id/11388

CPU: 1 PID: 11388 Comm: v4l_id Not tainted 5.9.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x107/0x16e lib/dump_stack.c:118
 print_address_description.constprop.0+0x1c/0x210 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x37/0x7c mm/kasan/report.c:530
 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+0x20f/0x3d0 drivers/media/v4l2-core/v4l2-dev.c:423
 chrdev_open+0x266/0x770 fs/char_dev.c:414
 do_dentry_open+0x4b4/0x1090 fs/open.c:817
 do_open fs/namei.c:3251 [inline]
 path_openat+0x190d/0x2690 fs/namei.c:3368
 do_filp_open+0x17e/0x3c0 fs/namei.c:3395
 do_sys_openat2+0x16d/0x420 fs/open.c:1168
 do_sys_open fs/open.c:1184 [inline]
 __do_sys_open fs/open.c:1192 [inline]
 __se_sys_open fs/open.c:1188 [inline]
 __x64_sys_open+0x119/0x1c0 fs/open.c:1188
 do_syscall_64+0x2d/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fee3e895840
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:00007ffc37239888 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007ffc372399f8 RCX: 00007fee3e895840
RDX: 00007fee3e881ea0 RSI: 0000000000000000 RDI: 00007ffc37239f22
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000555d9d9f38d0
R13: 00007ffc372399f0 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:00000000914a1a5b refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1c7278
flags: 0x200000000000000()
raw: 0200000000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881c7278780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881c7278800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8881c7278880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                                           ^
 ffff8881c7278900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881c7278980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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