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Date:   Sat, 23 Mar 2019 13:16:00 -0700
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Subject: Re: WARNING in request_end
From:   syzbot <syzbot+ef054c4d3f64cd7f7cec@syzkaller.appspotmail.com>
To:     dvyukov@google.com, ebiederm@xmission.com, ktkhai@virtuozzo.com,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        miklos@szeredi.hu, mszeredi@redhat.com,
        syzkaller-bugs@googlegroups.com
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Sender: linux-kernel-owner@vger.kernel.org
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Hello,

syzbot has tested the proposed patch but the reproducer still triggered  
crash:
WARNING in request_end

WARNING: CPU: 0 PID: 16992 at fs/fuse/dev.c:390 request_end+0x836/0xac0  
fs/fuse/dev.c:390
kobject: '0:49' (000000001562c524): kobject_uevent_env
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 16992 Comm: syz-executor3 Not tainted 4.19.0-rc5+ #1
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+0x1db/0x2ce lib/dump_stack.c:113
  panic+0x263/0x51a kernel/panic.c:184
kobject: 'loop5' (0000000073db98f3): kobject_uevent_env
  __warn.cold+0x13b/0x1ba kernel/panic.c:536
  report_bug+0x263/0x2b0 lib/bug.c:186
kobject: 'loop5' (0000000073db98f3): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
  fixup_bug arch/x86/kernel/traps.c:178 [inline]
  fixup_bug arch/x86/kernel/traps.c:173 [inline]
  do_error_trap+0x200/0x4e0 arch/x86/kernel/traps.c:296
kobject: '0:49' (000000001562c524): fill_kobj_path: path  
= '/devices/virtual/bdi/0:49'
  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:993
kobject: '0:49' (000000001562c524): kobject_cleanup, parent           (null)
RIP: 0010:request_end+0x836/0xac0 fs/fuse/dev.c:390
Code: 3c 03 0f 8f 7d fe ff ff 48 8b bd 30 ff ff ff e8 b0 b4 3b ff e9 6c fe  
ff ff e8 a6 ad f8 fe 0f 0b e9 be fa ff ff e8 9a ad f8 fe <0f> 0b e9 fc fa  
ff ff e8 4e c7 c2 fe e8 a9 b4 3b ff e9 6a fb ff ff
RSP: 0018:ffff8801c099f5a8 EFLAGS: 00010293
RAX: ffff8801be90e040 RBX: 1ffff10038133eba RCX: ffffffff82858ce9
RDX: 0000000000000000 RSI: ffffffff828591f6 RDI: 0000000000000007
RBP: ffff8801c099f698 R08: ffff8801be90e040 R09: ffffed0037bc2c18
R10: ffffed0037bc2c17 R11: ffff8801bde160bb R12: ffff8801a5ca9800
R13: ffff8801bde16040 R14: ffff8801c099f670 R15: ffff8801a5ca9830
kobject: '0:49' (000000001562c524): calling ktype release
  fuse_dev_do_write+0x1888/0x3730 fs/fuse/dev.c:1917
kobject: '0:49': free name
kobject: '0:49' (000000005b47baa2): kobject_add_internal: parent: 'bdi',  
set: 'devices'
kobject: '0:49' (000000005b47baa2): kobject_uevent_env
  fuse_dev_write+0x191/0x240 fs/fuse/dev.c:1941
kobject: '0:49' (000000005b47baa2): fill_kobj_path: path  
= '/devices/virtual/bdi/0:49'
  call_write_iter include/linux/fs.h:1808 [inline]
  new_sync_write fs/read_write.c:474 [inline]
  __vfs_write+0x6e5/0xa80 fs/read_write.c:487
kobject: '0:56' (00000000a2a816b6): kobject_add_internal: parent: 'bdi',  
set: 'devices'
kobject: '0:56' (00000000a2a816b6): kobject_uevent_env
  vfs_write+0x20c/0x560 fs/read_write.c:549
  ksys_write+0x105/0x260 fs/read_write.c:598
kobject: '0:56' (00000000a2a816b6): fill_kobj_path: path  
= '/devices/virtual/bdi/0:56'
  __do_sys_write fs/read_write.c:610 [inline]
  __se_sys_write fs/read_write.c:607 [inline]
  __ia32_sys_write+0x71/0xb0 fs/read_write.c:607
  do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
  do_fast_syscall_32+0x333/0xf98 arch/x86/entry/common.c:397
kobject: '0:57' (000000002c3163ad): kobject_add_internal: parent: 'bdi',  
set: 'devices'
kobject: '0:57' (000000002c3163ad): kobject_uevent_env
  entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7fa0cb9
Code: 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 0c 24 c3 8b 1c 24 c3 90 90  
90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90  
90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f7f5a0cc EFLAGS: 00000296 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000200002c0
RDX: 0000000000000050 RSI: 0000000000000000 RDI: 0000000000000000
kobject: '0:57' (000000002c3163ad): fill_kobj_path: path  
= '/devices/virtual/bdi/0:57'
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


Tested on:

commit:         bc78abbd fuse: Fix use-after-free in fuse_dev_do_read()
git tree:        
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=175a556d200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=eb49a17588446b34
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386