linux-kernel - [syzbot] WARNING: refcount bug in gadgetfs_kill

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Message-ID: <000000000000cc732d05f0794cf7@google.com>
Date:   Thu, 22 Dec 2022 22:57:33 -0800
From:   syzbot <syzbot+ac031e7435393ad05df6@...kaller.appspotmail.com>
To:     gregkh@...uxfoundation.org, hbh25y@...il.com, jomajm@...il.com,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        mingo@...nel.org, rdunlap@...radead.org, stern@...land.harvard.edu,
        syzkaller-bugs@...glegroups.com
Subject: [syzbot] WARNING: refcount bug in gadgetfs_kill_sb

Hello,

syzbot found the following issue on:

HEAD commit:    a5541c0811a0 Merge branch 'for-next/core' into for-kernelci
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=1310cd10480000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cbd4e584773e9397
dashboard link: https://syzkaller.appspot.com/bug?extid=ac031e7435393ad05df6
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=151fd1f0480000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=122eacc8480000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4b7702208fb9/disk-a5541c08.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9ec0153ec051/vmlinux-a5541c08.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6f8725ad290a/Image-a5541c08.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ac031e7435393ad05df6@...kaller.appspotmail.com

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 3448 at lib/refcount.c:28 refcount_warn_saturate+0x1a0/0x1c8 lib/refcount.c:28
Modules linked in:
CPU: 1 PID: 3448 Comm: syz-executor242 Not tainted 6.1.0-rc8-syzkaller-33330-ga5541c0811a0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : refcount_warn_saturate+0x1a0/0x1c8 lib/refcount.c:28
lr : refcount_warn_saturate+0x1a0/0x1c8 lib/refcount.c:28
sp : ffff800012ed3c60
x29: ffff800012ed3c60 x28: ffff80000c40fe48 x27: 0000000000000006
x26: ffff0000c70d6508 x25: 0000000000000000 x24: ffff0000c70d6400
x23: 0000000000000000 x22: ffff80000f183000 x21: 0000000000000000
x20: 0000000000000003 x19: ffff80000d95e000 x18: 000000000000030d
x17: ffff80000c0cd83c x16: ffff80000dbe6158 x15: ffff0000cdd34ec0
x14: 0000000000000000 x13: 00000000ffffffff x12: ffff0000cdd34ec0
x11: ff808000081c4d64 x10: 0000000000000000 x9 : 6a9cd14bd183ed00
x8 : 6a9cd14bd183ed00 x7 : ffff80000816678c x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 0000000000000006 x1 : 0000000100000000 x0 : 0000000000000026
Call trace:
 refcount_warn_saturate+0x1a0/0x1c8 lib/refcount.c:28
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 put_dev drivers/usb/gadget/legacy/inode.c:159 [inline]
 gadgetfs_kill_sb+0xd4/0x104 drivers/usb/gadget/legacy/inode.c:2086
 deactivate_locked_super+0x70/0xe8 fs/super.c:332
 vfs_get_super fs/super.c:1190 [inline]
 get_tree_single+0x98/0xe8 fs/super.c:1207
 gadgetfs_get_tree+0x28/0x38 drivers/usb/gadget/legacy/inode.c:2068
 vfs_get_tree+0x40/0x140 fs/super.c:1531
 vfs_fsconfig_locked fs/fsopen.c:232 [inline]
 __do_sys_fsconfig fs/fsopen.c:439 [inline]
 __se_sys_fsconfig fs/fsopen.c:314 [inline]
 __arm64_sys_fsconfig+0x758/0x818 fs/fsopen.c:314
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
 el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x140 arch/arm64/kernel/syscall.c:197
 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584
irq event stamp: 442
hardirqs last  enabled at (441): [<ffff80000816681c>] raw_spin_rq_unlock_irq kernel/sched/sched.h:1366 [inline]
hardirqs last  enabled at (441): [<ffff80000816681c>] finish_lock_switch+0x94/0xe8 kernel/sched/core.c:4968
hardirqs last disabled at (442): [<ffff80000c084084>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last  enabled at (360): [<ffff80000801c82c>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32
softirqs last disabled at (358): [<ffff80000801c7f8>] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19
---[ end trace 0000000000000000 ]---


---
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