KASAN: use-after-free Read in v4l2_fh

KASAN: use-after-free Read in v4l2_fh_open
Status: upstream: reported C repro on 2021/02/15 15:18
Reported-by: syzbot+b2391895514ed9ef4a8e@syzkaller.appspotmail.com
First crash: 17d, last: 17d

Cause bisection: introduced by (bisect log) [ignored commit]:
commit f2c2e717642c66f7fe7e5dd69b2e8ff5849f4d10
Author: Andrey Konovalov <andreyknvl@google.com>
Date: Mon Feb 24 16:13:03 2020 +0000

usb: gadget: add raw-gadget interface

Crash: KASAN: use-after-free Read in v4l2_fh_init (log)
Repro: C syz .config

Sample crash report:

==================================================================
BUG: KASAN: use-after-free in v4l2_fh_init drivers/media/v4l2-core/v4l2-fh.c:25 [inline]
BUG: KASAN: use-after-free in v4l2_fh_open+0xc7/0x430 drivers/media/v4l2-core/v4l2-fh.c:63
Read of size 8 at addr ffff8880228b88b8 by task v4l_id/18349

CPU: 1 PID: 18349 Comm: v4l_id Not tainted 5.11.0-rc7-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+0x137/0x1be lib/dump_stack.c:120
 print_address_description+0x5f/0x3a0 mm/kasan/report.c:230
 __kasan_report mm/kasan/report.c:396 [inline]
 kasan_report+0x15e/0x200 mm/kasan/report.c:413
 v4l2_fh_init drivers/media/v4l2-core/v4l2-fh.c:25 [inline]
 v4l2_fh_open+0xc7/0x430 drivers/media/v4l2-core/v4l2-fh.c:63
 em28xx_v4l2_open+0x15c/0xa60 drivers/media/usb/em28xx/em28xx-video.c:2163
 v4l2_open+0x229/0x360 drivers/media/v4l2-core/v4l2-dev.c:423
 chrdev_open+0x4a0/0x570 fs/char_dev.c:414
 do_dentry_open+0x7cb/0x1010 fs/open.c:817
 do_open fs/namei.c:3254 [inline]
 path_openat+0x2791/0x37a0 fs/namei.c:3371
 do_filp_open+0x191/0x3a0 fs/namei.c:3398
 do_sys_openat2+0xba/0x380 fs/open.c:1172
 do_sys_open fs/open.c:1188 [inline]
 __do_sys_open fs/open.c:1196 [inline]
 __se_sys_open fs/open.c:1192 [inline]
 __x64_sys_open+0x1af/0x1e0 fs/open.c:1192
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fdd62b00840
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:00007ffe8bb255b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007ffe8bb25728 RCX: 00007fdd62b00840
RDX: 00007fdd62aecea0 RSI: 0000000000000000 RDI: 00007ffe8bb26f1c
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 000055f8a7dee8d0
R13: 00007ffe8bb25720 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:00000000b7dd9778 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x228b8
flags: 0xfff00000000000()
raw: 00fff00000000000 ffffea0000580108 ffff88813fffb910 0000000000000000
raw: 0000000000000000 0000000000000002 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880228b8780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880228b8800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880228b8880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                        ^
 ffff8880228b8900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880228b8980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci-upstream-kasan-gce-smack-root	2021/02/11 15:12	upstream	291009f6	a52ee10a	.config	log	report	syz	C		KASAN: use-after-free Read in v4l2_fh_open