WARNING in request_end

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 6bf4ca7fbc85 Linux 4.19-rc5
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=159149c6400000
kernel config: https://syzkaller.appspot.com/x/.config?x=22a62640793a83c9
dashboard link: https://syzkaller.appspot.com/bug?extid=ef054c4d3f64cd7f7cec
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ef054c...@syzkaller.appspotmail.com

WARNING: CPU: 0 PID: 9445 at fs/fuse/dev.c:390 request_end+0x82e/0xaa0
fs/fuse/dev.c:390
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 9445 Comm: syz-executor2 Not tainted 4.19.0-rc5+ #251
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
kobject: '0:56' (00000000d57a9914): kobject_add_internal: parent: 'bdi',
set: 'devices'
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
kobject: '0:56' (00000000d57a9914): kobject_uevent_env
panic+0x238/0x4e7 kernel/panic.c:184
kobject: '0:56' (00000000d57a9914): fill_kobj_path: path
= '/devices/virtual/bdi/0:56'
__warn.cold.8+0x163/0x1ba kernel/panic.c:536
report_bug+0x254/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:993
RIP: 0010:request_end+0x82e/0xaa0 fs/fuse/dev.c:390
Code: 3c 03 0f 8f 6f fe ff ff 48 8b bd f0 fe ff ff e8 68 e7 39 ff e9 5e fe
ff ff e8 8e 86 f6 fe 0f 0b e9 b0 fa ff ff e8 82 86 f6 fe <0f> 0b e9 f0 fa
ff ff e8 36 71 c0 fe e8 61 e7 39 ff e9 5b fb ff ff
RSP: 0018:ffff88019df0f378 EFLAGS: 00010212
RAX: 0000000000040000 RBX: ffff8801d2ca6000 RCX: ffffc90006d53000
RDX: 0000000000000138 RSI: ffffffff82885d9e RDI: 0000000000000007
RBP: ffff88019df0f4a8 R08: ffff8801d1a6c200 R09: ffffed0034b53937
R10: ffffed0034b53937 R11: ffff8801a5a9c9bb R12: 1ffff10033be1e74
R13: ffff8801a5a9c940 R14: ffff8801d2ca6030 R15: ffff88019df0f480
fuse_dev_do_write+0x192e/0x36e0 fs/fuse/dev.c:1915
fuse_dev_write+0x19a/0x240 fs/fuse/dev.c:1939
call_write_iter include/linux/fs.h:1808 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x6b8/0x9f0 fs/read_write.c:487
vfs_write+0x1fc/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457679
Code: 1d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007efd81affc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007efd81b006d4 RCX: 0000000000457679
RDX: 0000000000000090 RSI: 0000000020000500 RDI: 0000000000000003
RBP: 000000000072c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d8710 R14: 00000000004c50a2 R15: 0000000000000002
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.

[Miklos Szeredi]

On Mon, Sep 24, 2018 at 2:29 PM, syzbot
<syzbot+ef054c...@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 6bf4ca7fbc85 Linux 4.19-rc5
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=159149c6400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=22a62640793a83c9
> dashboard link: https://syzkaller.appspot.com/bug?extid=ef054c4d3f64cd7f7cec
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+ef054c...@syzkaller.appspotmail.com
>
> WARNING: CPU: 0 PID: 9445 at fs/fuse/dev.c:390 request_end+0x82e/0xaa0

And there we have the bug likely caused by the set_bit(FR_SENT, ...)
not being inside the fpq->lock-ed region.

So that needs to be fixed anyway, apparently.

Thanks,
Miklos

[Kirill Tkhai]

I can't confirm, since I haven't found yet the direct way, that set_bit() results
in this stack...

We have one more (unrelated) possible use-after-free here:

cpu0 cpu1
fuse_dev_do_write() fuse_dev_do_write()
req = request_find(fpq, oh.unique) ...
spin_unlock(&fpq->lock) ...
... req = request_find(fpq, oh.unique)
... spin_unlock(&fpq->lock)
queue_interrupt(&fc->iq, req); ...
... ...
... ...
request freed ...
... queue_interrupt(&fc->iq, req); <- use after free

Something like below is needed:

@@ -1875,16 +1877,20 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud,

/* Is it an interrupt reply? */
if (req->intr_unique == oh.unique) {
+ __fuse_get_request(req);
spin_unlock(&fpq->lock);

err = -EINVAL;
- if (nbytes != sizeof(struct fuse_out_header))
+ if (nbytes != sizeof(struct fuse_out_header)) {
+ fuse_put_request(fc, req);
goto err_finish;
+ }

if (oh.error == -ENOSYS)
fc->no_interrupt = 1;
else if (oh.error == -EAGAIN)
queue_interrupt(&fc->iq, req);
+ fuse_put_request(fc, req);

fuse_copy_finish(cs);
return nbytes;

[Dmitry Vyukov]

There is a bunch of open bugs in fuse on syzbot dashboard, perhaps
it's one of them:

https://syzkaller.appspot.com/bug?id=19aabec97cbf73dd0475d6e599113a7861c4b306
https://syzkaller.appspot.com/bug?id=24aa489e6929205e40ec4aa52cd8f47897f2ad63
https://syzkaller.appspot.com/bug?id=400d6a977a0dbd8836d7c7ec8481782a674ee855
https://syzkaller.appspot.com/bug?id=ff9ab4a23afa7553fb79f745a92be87ba4144508
https://syzkaller.appspot.com/bug?id=d0f258de27b6d7ccecbba09385b3376cc4a12ffe
https://syzkaller.appspot.com/bug?id=e8077bce636d52d9c40e1ea904699c27b7454354

> @@ -1875,16 +1877,20 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud,
>
> /* Is it an interrupt reply? */
> if (req->intr_unique == oh.unique) {
> + __fuse_get_request(req);
> spin_unlock(&fpq->lock);
>
> err = -EINVAL;
> - if (nbytes != sizeof(struct fuse_out_header))
> + if (nbytes != sizeof(struct fuse_out_header)) {
> + fuse_put_request(fc, req);
> goto err_finish;
> + }
>
> if (oh.error == -ENOSYS)
> fc->no_interrupt = 1;
> else if (oh.error == -EAGAIN)
> queue_interrupt(&fc->iq, req);
> + fuse_put_request(fc, req);
>
> fuse_copy_finish(cs);
> return nbytes;
>

> --
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> For more options, visit https://groups.google.com/d/optout.

[Kirill Tkhai]

I can't find fuse_dev_do_write() there, but it's possible this race could appear
in another function. So, Dmitry, I won't add reference to one of tham. Let's
check, which will disappear in the future.

Thanks,
Kirill

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 0238df646e62 Linux 4.19-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16daaa85400000
kernel config: https://syzkaller.appspot.com/x/.config?x=88e9a8a39dc0be2d

dashboard link: https://syzkaller.appspot.com/bug?extid=ef054c4d3f64cd7f7cec
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=119bf2e6400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1760f806400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ef054c...@syzkaller.appspotmail.com

8021q: adding VLAN 0 to HW filter on device team0
8021q: adding VLAN 0 to HW filter on device team0
WARNING: CPU: 1 PID: 7459 at fs/fuse/dev.c:390 request_end+0x82e/0xaa0

fs/fuse/dev.c:390
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 7459 Comm: syz-executor659 Not tainted 4.19.0-rc7+ #176

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+0x1c4/0x2b4 lib/dump_stack.c:113

panic+0x238/0x4e7 kernel/panic.c:184

__warn.cold.8+0x163/0x1ba kernel/panic.c:536
report_bug+0x254/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:993
RIP: 0010:request_end+0x82e/0xaa0 fs/fuse/dev.c:390

Code: 3c 03 0f 8f 6f fe ff ff 48 8b bd f0 fe ff ff e8 78 63 3b ff e9 5e fe
ff ff e8 1e f3 f7 fe 0f 0b e9 b0 fa ff ff e8 12 f3 f7 fe <0f> 0b e9 f0 fa
ff ff e8 16 ca c1 fe e8 71 63 3b ff e9 5b fb ff ff
RSP: 0018:ffff8801c65e7328 EFLAGS: 00010293
RAX: ffff8801cd3362c0 RBX: ffff8801cba17000 RCX: ffffffff8286dd65
RDX: 0000000000000000 RSI: ffffffff8286e27e RDI: 0000000000000007
RBP: ffff8801c65e7458 R08: ffff8801cd3362c0 R09: ffffed00391cd5bf
R10: ffffed00391cd5bf R11: ffff8801c8e6adfb R12: 1ffff10038cbce6a
R13: ffff8801c8e6ad80 R14: ffff8801cba17030 R15: ffff8801c65e7430

fuse_dev_do_write+0x192e/0x36e0 fs/fuse/dev.c:1915
fuse_dev_write+0x19a/0x240 fs/fuse/dev.c:1939
call_write_iter include/linux/fs.h:1808 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x6b8/0x9f0 fs/read_write.c:487
vfs_write+0x1fc/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__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+0x34d/0xfb2 arch/x86/entry/common.c:397
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f43ca9
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:00000000f7efd1fc EFLAGS: 00000246 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000200002c0
RDX: 0000000000000050 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00000000003d0f00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

[syzbot]

syzbot has bisected this bug to:

commit 4ad769f3c346ec3d458e255548dec26ca5284cf6
Author: Eric W. Biederman <ebie...@xmission.com>
Date: Tue May 29 14:04:46 2018 +0000

fuse: Allow fully unprivileged mounts

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=16b4518b200000
start commit: 0238df64 Linux 4.19-rc7
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=15b4518b200000
console output: https://syzkaller.appspot.com/x/log.txt?x=11b4518b200000

kernel config: https://syzkaller.appspot.com/x/.config?x=88e9a8a39dc0be2d
dashboard link: https://syzkaller.appspot.com/bug?extid=ef054c4d3f64cd7f7cec

userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=119bf2e6400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1760f806400000

Reported-by: syzbot+ef054c...@syzkaller.appspotmail.com
Fixes: 4ad769f3c346 ("fuse: Allow fully unprivileged mounts")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Eric W. Biederman]

syzbot <syzbot+ef054c...@syzkaller.appspotmail.com> writes:

> syzbot has bisected this bug to:

Nope. syzbot got it wrong.

At most that commit will allow a larger class of users to mount fuse
and thus be able to reproduce the problem.

It does look like syzbot has found something concerning though.

Miklos any ideas?

From https://syzkaller.appspot.com/x/report.txt?x=15b4518b200000
> [ 448.045793] ==================================================================
> [ 448.053414] BUG: KASAN: use-after-free in fuse_dev_do_read.isra.24+0x166f/0x1be0
> [ 448.060937] Read of size 8 at addr ffff8801cec98430 by task syz-executor0/9001
> [ 448.068286]
> [ 448.069901] CPU: 1 PID: 9001 Comm: syz-executor0 Not tainted 4.16.0-rc6+ #1
> [ 448.076990] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> [ 448.086330] Call Trace:
> [ 448.089107] dump_stack+0x153/0x201
> [ 448.092926] ? arch_local_irq_restore+0x43/0x43
> [ 448.097579] ? printk+0x9a/0xc0
> [ 448.100844] ? show_regs_print_info+0xb/0xb
> [ 448.105265] print_address_description.cold.7+0x9/0x1c9
> [ 448.110739] kasan_report.cold.8+0x242/0x2fe
> [ 448.115255] ? fuse_dev_do_read.isra.24+0x166f/0x1be0
> [ 448.120476] __asan_report_load8_noabort+0x14/0x20
> [ 448.125393] fuse_dev_do_read.isra.24+0x166f/0x1be0
> [ 448.130397] ? debug_check_no_locks_freed+0x310/0x310
> [ 448.135574] ? end_requests+0x470/0x470
> [ 448.139529] ? print_usage_bug+0xc0/0xc0
> [ 448.143576] ? prepare_to_wait+0x4f0/0x4f0
> [ 448.147932] ? print_usage_bug+0xc0/0xc0
> [ 448.152139] ? __unqueue_futex+0x270/0x270
> [ 448.156376] ? add_lock_to_list.isra.29+0x4b0/0x4b0
> [ 448.161703] ? wake_up_q+0x9c/0xe0
> [ 448.165236] ? futex_wake+0x245/0x8a0
> [ 448.169025] ? find_held_lock+0x36/0x1c0
> [ 448.173085] ? aa_file_perm+0x319/0xda0
> [ 448.177065] ? lock_downgrade+0x900/0x900
> [ 448.181241] ? rcu_read_lock_bh_held+0xc0/0xc0
> [ 448.185813] ? debug_smp_processor_id+0x17/0x20
> [ 448.190557] ? rcu_is_watching+0x69/0x180
> [ 448.194700] ? __lock_is_held+0xb5/0x140
> [ 448.198859] ? rcu_dynticks_eqs_exit+0x70/0x70
> [ 448.203436] ? aa_file_perm+0x336/0xda0
> [ 448.207393] ? rcu_read_lock_bh_held+0xc0/0xc0
> [ 448.211958] ? aa_path_link+0x610/0x610
> [ 448.215913] ? rcu_dynticks_eqs_exit+0x70/0x70
> [ 448.220485] ? memset+0x31/0x40
> [ 448.223752] fuse_dev_read+0x185/0x240
> [ 448.227665] ? fuse_dev_splice_read+0x7a0/0x7a0
> [ 448.232375] ? find_held_lock+0x36/0x1c0
> [ 448.236439] __vfs_read+0x54a/0xd20
> [ 448.240161] ? debug_lockdep_rcu_enabled+0x77/0x90
> [ 448.245069] ? vfs_copy_file_range+0xb60/0xb60
> [ 448.249737] ? fsnotify_first_mark+0x280/0x280
> [ 448.254360] ? rw_verify_area+0xb8/0x2b0
> [ 448.258411] ? __fdget_raw+0x10/0x10
> [ 448.262151] vfs_read+0xf5/0x300
> [ 448.265509] SyS_read+0xf5/0x250
> [ 448.268860] ? kernel_write+0x130/0x130
> [ 448.272823] ? do_fast_syscall_32+0x151/0x1016
> [ 448.277396] do_fast_syscall_32+0x3d5/0x1016
> [ 448.281797] ? _raw_spin_unlock_irq+0x27/0x80
> [ 448.286317] ? trace_hardirqs_on_caller+0x421/0x5c0
> [ 448.291337] ? do_int80_syscall_32+0x9f0/0x9f0
> [ 448.296277] ? _raw_spin_unlock_irq+0x60/0x80
> [ 448.300761] ? finish_task_switch+0x1f4/0x890
> [ 448.305411] ? syscall_return_slowpath+0x215/0x4e0
> [ 448.310337] ? prepare_exit_to_usermode+0x300/0x300
> [ 448.315348] ? sysret32_from_system_call+0x5/0x3c
> [ 448.320187] ? trace_hardirqs_off_thunk+0x1a/0x1c
> [ 448.325080] entry_SYSENTER_compat+0x70/0x7f
> [ 448.329492] RIP: 0023:0xf7f8fcb9
> [ 448.332846] RSP: 002b:00000000f7f8b0cc EFLAGS: 00000296 ORIG_RAX: 0000000000000003
> [ 448.340546] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000020001000
> [ 448.347796] RDX: 00000000ffffff20 RSI: 0000000000000000 RDI: 0000000000000000
> [ 448.355047] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> [ 448.362301] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> [ 448.369595] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> [ 448.376890]
> [ 448.378514] Allocated by task 9010:
> [ 448.382133] save_stack+0x43/0xd0
> [ 448.385681] kasan_kmalloc+0xc7/0xe0
> [ 448.389408] kasan_slab_alloc+0x12/0x20
> [ 448.393373] kmem_cache_alloc+0x12e/0x790
> [ 448.397518] __fuse_request_alloc+0x23/0xc0
> [ 448.401827] __fuse_get_req+0x186/0x8d0
> [ 448.405790] fuse_simple_request+0x20/0x610
> [ 448.410101] fuse_do_setattr+0x820/0x1f60
> [ 448.414262] fuse_setattr+0x1a6/0x470
> [ 448.418074] notify_change+0x779/0xda0
> [ 448.421942] utimes_common.isra.1+0x3f8/0x7f0
> [ 448.426420] do_utimes+0x199/0x250
> [ 448.430053] compat_SyS_utimes+0x1f8/0x2e0
> [ 448.434563] do_fast_syscall_32+0x3d5/0x1016
> [ 448.438956] entry_SYSENTER_compat+0x70/0x7f
> [ 448.443357]
> [ 448.444974] Freed by task 9010:
> [ 448.448305] save_stack+0x43/0xd0
> [ 448.451740] __kasan_slab_free+0x102/0x150
> [ 448.455957] kasan_slab_free+0xe/0x10
> [ 448.459750] kmem_cache_free+0x83/0x2d0
> [ 448.463719] fuse_request_free+0x77/0x90
> [ 448.467762] fuse_put_request+0x22a/0x2d0
> [ 448.471901] fuse_simple_request+0x38a/0x610
> [ 448.476394] fuse_do_setattr+0x820/0x1f60
> [ 448.480525] fuse_setattr+0x1a6/0x470
> [ 448.484304] notify_change+0x779/0xda0
> [ 448.488342] utimes_common.isra.1+0x3f8/0x7f0
> [ 448.492918] do_utimes+0x199/0x250
> [ 448.496443] compat_SyS_utimes+0x1f8/0x2e0
> [ 448.500769] do_fast_syscall_32+0x3d5/0x1016
> [ 448.505172] entry_SYSENTER_compat+0x70/0x7f
> [ 448.509660]
> [ 448.511273] The buggy address belongs to the object at ffff8801cec98400
> [ 448.511273] which belongs to the cache fuse_request of size 448
> [ 448.524116] The buggy address is located 48 bytes inside of
> [ 448.524116] 448-byte region [ffff8801cec98400, ffff8801cec985c0)
> [ 448.535897] The buggy address belongs to the page:
> [ 448.540853] page:ffffea00073b2600 count:1 mapcount:0 mapping:ffff8801cec98000 index:0x0
> [ 448.549166] flags: 0x2fffc0000000100(slab)
> [ 448.553534] raw: 02fffc0000000100 ffff8801cec98000 0000000000000000 0000000100000008
> [ 448.561407] raw: ffffea0007656660 ffffea00076359e0 ffff8801d4de8680 0000000000000000
> [ 448.569270] page dumped because: kasan: bad access detected
> [ 448.574960]
> [ 448.576564] Memory state around the buggy address:
> [ 448.581477] ffff8801cec98300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [ 448.588871] ffff8801cec98380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> [ 448.596217] >ffff8801cec98400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [ 448.603596] ^
> [ 448.608507] ffff8801cec98480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [ 448.615843] ffff8801cec98500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [ 448.623284] ==================================================================

Eric

[Miklos Szeredi]

On Sat, Mar 23, 2019 at 4:52 PM Eric W. Biederman <ebie...@xmission.com> wrote:
>
> syzbot <syzbot+ef054c...@syzkaller.appspotmail.com> writes:
>
> > syzbot has bisected this bug to:
>
> Nope. syzbot got it wrong.
>
> At most that commit will allow a larger class of users to mount fuse
> and thus be able to reproduce the problem.
>
> It does look like syzbot has found something concerning though.
>
> Miklos any ideas?

Dup of this?

bc78abbd55dd ("fuse: Fix use-after-free in fuse_dev_do_read()")

Let's test:

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
bc78abbd55dd

Thanks,
Miklos

[syzbot]

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

[syzbot]

syzbot suspects this bug was fixed by commit:

commit 4c316f2f3ff315cb48efb7435621e5bfb81df96d
Author: Miklos Szeredi <msze...@redhat.com>
Date: Fri Sep 28 14:43:22 2018 +0000

fuse: set FR_SENT while locked

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=113124ba600000

start commit: 0238df64 Linux 4.19-rc7
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=88e9a8a39dc0be2d
dashboard link: https://syzkaller.appspot.com/bug?extid=ef054c4d3f64cd7f7cec
userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=119bf2e6400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1760f806400000

If the result looks correct, please mark the bug fixed by replying with:

#syz fix: fuse: set FR_SENT while locked

[syzbot]

> That commit has corrupted truncated "Reported-by:" line.

> #syz fix: fuse: set FR_SENT while locked

Your 'fix:' command is accepted, but please keep
syzkall...@googlegroups.com mailing list in CC next time. It serves as
a history of what happened with each bug report. Thank you.