general protection fault in lo_ioctl

[syzbot]

Hello,

syzkaller hit the following crash on
c52f56a69d104d5294af3d652776d94b1ef6a175
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.




kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 7227 Comm: syz-executor5 Not tainted 4.14.0-rc1+ #93
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
task: ffff8801c32ae200 task.stack: ffff8801d9aa8000
RIP: 0010:loop_set_fd drivers/block/loop.c:885 [inline]
RIP: 0010:lo_ioctl+0x678/0x1b80 drivers/block/loop.c:1353
RSP: 0018:ffff8801d9aafaa0 EFLAGS: 00010202
RAX: 0000000000010000 RBX: dffffc0000000000 RCX: ffffc9000448e000
RDX: 000000000000003b RSI: ffffffff83541738 RDI: 00000000000001d8
RBP: ffff8801d9aafb18 R08: ffffffff85b382a0 R09: 1ffff1003b355efd
R10: ffff8801c32ae200 R11: 0000000000000001 R12: 0000000000000000
R13: ffff8801d4ff7200 R14: ffff8801d6551100 R15: ffff8801d4ff7358
FS: 00007f63068df700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f783dc354a0 CR3: 00000001d78d6000 CR4: 00000000001426f0
DR0: 0000000020000008 DR1: 0000000020000008 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
__blkdev_driver_ioctl block/ioctl.c:297 [inline]
blkdev_ioctl+0xc07/0x1de0 block/ioctl.c:594
block_ioctl+0xea/0x130 fs/block_dev.c:1870
vfs_ioctl fs/ioctl.c:45 [inline]
do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:685
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x4520a9
RSP: 002b:00007f63068dec08 EFLAGS: 00000216 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000007180b0 RCX: 00000000004520a9
RDX: 0000000000000016 RSI: 0000000000004c00 RDI: 0000000000000006
RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000216 R12: 0000000000000000
R13: 0000000000a6f7ef R14: 00007f63068df9c0 R15: 0000000000000023
Code: 00 00 00 48 89 fa 48 c1 ea 03 80 3c 1a 00 0f 85 81 14 00 00 4d 8b a4
24 f0 00 00 00 49 8d bc 24 d8 01 00 00 48 89 fa 48 c1 ea 03 <80> 3c 1a 00
0f 85 56 14 00 00 4d 8b a4 24 d8 01 00 00 4c 89 e2
RIP: loop_set_fd drivers/block/loop.c:885 [inline] RSP: ffff8801d9aafaa0
RIP: lo_ioctl+0x678/0x1b80 drivers/block/loop.c:1353 RSP: ffff8801d9aafaa0
---[ end trace 249e5d44fb303080 ]---
sctp: [Deprecated]: syz-executor1 (pid 7255) Use of struct sctp_assoc_value
in delayed_ack socket option.
Use struct sctp_sack_info instead
netlink: 5 bytes leftover after parsing attributes in process
`syz-executor3'.
IPv6: Can't replace route, no match found
sctp: [Deprecated]: syz-executor1 (pid 7255) Use of struct sctp_assoc_value
in delayed_ack socket option.
Use struct sctp_sack_info instead
SELinux: unrecognized netlink message: protocol=6 nlmsg_type=65535
sclass=netlink_xfrm_socket pig=7254 comm=syz-executor3
netlink: 60 bytes leftover after parsing attributes in process
`syz-executor3'.
IPv6: Can't replace route, no match found
SELinux: unrecognized netlink message: protocol=6 nlmsg_type=65535
sclass=netlink_xfrm_socket pig=7266 comm=syz-executor3
sctp: [Deprecated]: syz-executor1 (pid 7274) Use of struct sctp_assoc_value
in delayed_ack socket option.
Use struct sctp_sack_info instead
IPv6: Can't replace route, no match found
SELinux: unrecognized netlink message: protocol=6 nlmsg_type=65535
sclass=netlink_xfrm_socket pig=7283 comm=syz-executor3
IPv6: Can't replace route, no match found
SELinux: unrecognized netlink message: protocol=6 nlmsg_type=65535
sclass=netlink_xfrm_socket pig=7283 comm=syz-executor3


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzk...@googlegroups.com.
Please credit me with: Reported-by: syzbot <syzk...@googlegroups.com>

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[Dmitry Vyukov]

On Fri, Nov 3, 2017 at 4:01 PM, syzbot
<bot+b87b24db14d35489d4...@syzkaller.appspotmail.com>
wrote:

This also happened on more recent commits, including linux-next
36ef71cae353f88fd6e095e2aaa3e5953af1685d (oct 19):

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:

CPU: 2 PID: 4083 Comm: syz-executor6 Not tainted 4.14.0-rc5-next-20171018+ #8
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88006c556440 task.stack: ffff88006b198000
RIP: 0010:loop_set_fd drivers/block/loop.c:890 [inline]
RIP: 0010:lo_ioctl+0x672/0x1b70 drivers/block/loop.c:1358
print_req_error: I/O error, dev loop3, sector 0
Buffer I/O error on dev loop3, logical block 0, lost async page write
print_req_error: I/O error, dev loop3, sector 8
Buffer I/O error on dev loop3, logical block 1, lost async page write
print_req_error: I/O error, dev loop3, sector 16
Buffer I/O error on dev loop3, logical block 2, lost async page write
print_req_error: I/O error, dev loop3, sector 24
Buffer I/O error on dev loop3, logical block 3, lost async page write
print_req_error: I/O error, dev loop3, sector 32
Buffer I/O error on dev loop3, logical block 4, lost async page write
print_req_error: I/O error, dev loop3, sector 40
Buffer I/O error on dev loop3, logical block 5, lost async page write
print_req_error: I/O error, dev loop3, sector 48
Buffer I/O error on dev loop3, logical block 6, lost async page write
print_req_error: I/O error, dev loop3, sector 56
Buffer I/O error on dev loop3, logical block 7, lost async page write
print_req_error: I/O error, dev loop3, sector 64
Buffer I/O error on dev loop3, logical block 8, lost async page write
print_req_error: I/O error, dev loop3, sector 72
Buffer I/O error on dev loop3, logical block 9, lost async page write
RSP: 0018:ffff88006b19faa0 EFLAGS: 00010202
RAX: 0000000000010000 RBX: dffffc0000000000 RCX: ffffffff8365b372
RDX: 0000000000000037 RSI: ffffc90003814000 RDI: 00000000000001b8
RBP: ffff88006b19fb18 R08: 0000000000000001 R09: 1ffff1000d633f05
R10: ffff88006b19f7f0 R11: 0000000000000001 R12: 0000000000000000
R13: ffff88006b628000 R14: ffff88006d45a680 R15: ffff88006b628150
FS: 00007f047db9f700(0000) GS:ffff88006de00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000020766fc5 CR3: 000000004d2b4000 CR4: 00000000000026e0
DR0: 0000000020000000 DR1: 0000000020001000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600

Call Trace:
__blkdev_driver_ioctl block/ioctl.c:297 [inline]
blkdev_ioctl+0xc07/0x1de0 block/ioctl.c:594

block_ioctl+0xde/0x120 fs/block_dev.c:1860
vfs_ioctl fs/ioctl.c:45 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685

SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
entry_SYSCALL_64_fastpath+0x1f/0xbe

RIP: 0033:0x447c89
RSP: 002b:00007f047db9ebd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f047db9f6cc RCX: 0000000000447c89
RDX: 0000000000000013 RSI: 0000000000004c00 RDI: 0000000000000014

RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000004020 R14: 00000000006e80c0 R15: 00007f047db9f700
Code: 00 00 00 48 89 fa 48 c1 ea 03 80 3c 1a 00 0f 85 6f 14 00 00 4d
8b a4 24 f0 00 00 00 49 8d bc 24 b8 01 00 00 48 89 fa 48 c1 ea 03 <80>
3c 1a 00 0f 85 44 14 00 00 4d 8b a4 24 b8 01 00 00 4c 89 e2
RIP: loop_set_fd drivers/block/loop.c:890 [inline] RSP: ffff88006b19faa0
RIP: lo_ioctl+0x672/0x1b70 drivers/block/loop.c:1358 RSP: ffff88006b19faa0
---[ end trace 6a5ea439dc513bfe ]---

> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzk...@googlegroups.com.
> Please credit me with: Reported-by: syzbot <syzk...@googlegroups.com>
>
> syzbot will keep track of this bug report.
> Once a fix for this bug is committed, please reply to this email with:
> #syz fix: exact-commit-title
> To mark this as a duplicate of another syzbot report, please reply with:
> #syz dup: exact-subject-of-another-report
> If it's a one-off invalid bug report, please reply with:
> #syz invalid
> Note: if the crash happens again, it will cause creation of a new bug
> report.
> Note: all commands must start from beginning of the line.
>

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[Dmitry Vyukov]

Now difficult to say what happened -- if it was fixed or something
else. But it last happened 3+ months ago so:

#syz invalid