On 2021-07-27 at 15:39, Krzysztof Olędzki wrote:
> On 2021-07-27 at 14:53, Krzysztof Olędzki wrote:
>> Hi,
>>
>> I have a number of (older) systems that are still based on 32 bit
>> userspace but are running a relatively modern 64 bit kernel -
>> 5.4-stable, where BTW - LOOP_CONFIGURE is not yet available.
>>
>> I noticed that starting with util-linux-2.37 it is no longer possible to
>> mount images using loop:
>>
>> # mount /usr/install/iso/systemrescue-8.04-amd64.iso /mnt/cdrom
>> mount: /mnt/cdrom: failed to setup loop device for
>> /usr/install/iso/systemrescue-8.04-amd64.iso.
>>
>> Reverting d5fd456c88aba4fcf77d35fe38024a8d5c814686 fixes the problem:
>>
>> /tmp/util-linux-2.37# ./mount
>> /usr/install/iso/systemrescue-8.04-amd64.iso /mnt/cdrom
>> mount: /mnt/cdrom: WARNING: source write-protected, mounted read-only.
>>
>> I have not tested if 32 bit kernel + 32 bit userspace is also affected,
>> but 64 bit kernel + 64 bit userspace works.
>
> Some debugging data:
>
> 30399: loopdev: CXT: [0xff8d0f98]: using loop-control
> 30399: loopdev: CXT: [0xff8d0f98]: loop0 name assigned
> 30399: loopdev: CXT: [0xff8d0f98]: find_unused by loop-control [rc=0]
> 30399: libmount: LOOP: [0x57cbbcb0]: trying to use /dev/loop0
> 30399: loopdev: CXT: [0xff8d0f98]: set backing file=/usr/install/iso/systemrescue-8.04-amd64.iso
> 30399: loopdev: CXT: [0xff8d0f98]: set flags=4
> 30399: loopdev: SETUP: [0xff8d0f98]: device setup requested
> 30399: loopdev: SETUP: [0xff8d0f98]: backing file open: OK
> 30399: loopdev: CXT: [0xff8d0f98]: open /dev/loop0 [rw]: Success
> 30399: loopdev: SETUP: [0xff8d0f98]: device open: OK
> 30399: loopdev: SETUP: [0xff8d0f98]: LOOP_CONFIGURE failed: Inappropriate ioctl for device
> 30399: loopdev: SETUP: [0xff8d0f98]: failed [rc=-25]
> 30399: libmount: LOOP: [0x57cbbcb0]: failed to setup device
> 30399: loopdev: CXT: [0xff8d0f98]: de-initialize
> 30399: loopdev: CXT: [0xff8d0f98]: closing old open fd
> 30399: loopdev: ITER: [0xff8d1168]: de-initialize
> 30399: libmount: CXT: [0x57cbbcb0]: mount: preparing failed
> 30399: libmount: CXT: [0x57cbbcb0]: excode: rc=32 message="failed to setup loop device for /usr/install/iso/systemrescue-8.04-amd64.iso"
> mount: /mnt/cdrom: failed to setup loop device for /usr/install/iso/systemrescue-8.04-amd64.iso.
> 30399: libmount: CXT: [0x57cbbcb0]: <---- reset [status=0] ---->
>
> Seems like the code expects EINVAL (-22) but gets ENOTTY (-25), confirmed with strace:
> ioctl(4, LOOP_CONFIGURE, {fd=3, block_size=0, info={lo_offset=0, lo_number=0, lo_flags=LO_FLAGS_AUTOCLEAR, lo_file_name="/usr/install/iso/systemrescue-8.04-amd64.iso", ...}}) = -1 ENOTTY (Inappropriate ioctl for device)
>
> Indeed, changing the code from:
> if (errno != EINVAL)
> to:
> if (errno != EINVAL && errno != ENOTTY)
> allows it to work.
>
> Not that with 64-bit userspace, kernel returns EINVAL:
>
> ioctl(4, LOOP_CONFIGURE, {fd=3, block_size=0, info={lo_offset=0, lo_number=0, lo_flags=LO_FLAGS_AUTOCLEAR, lo_file_name="/usr/src/PACKAGES/systemrescue-8.04-amd64.iso", ...}}) = -1 EINVAL (Invalid argument)
... which is because lo_compat_ioctl returns -ENOIOCTLCMD for
unsupported cmds, while lo_ioctl returns -EINVAL via lo_simple_ioctl.
And vfs_ioctl returns -ENOTTY for -ENOIOCTLCMD.
Now the question is if this inconsistency is intended? :)
Krzysztof
On 7/27/21 4:56 PM, Krzysztof Olędzki wrote:
> On 2021-07-27 at 15:39, Krzysztof Olędzki wrote:
>> On 2021-07-27 at 14:53, Krzysztof Olędzki wrote:
>>> Hi,
>>>
>>> I have a number of (older) systems that are still based on 32 bit
>>> userspace but are running a relatively modern 64 bit kernel -
>>> 5.4-stable, where BTW - LOOP_CONFIGURE is not yet available.
>>>
>>> I noticed that starting with util-linux-2.37 it is no longer possible to
>>> mount images using loop:
>>>
>>> # mount /usr/install/iso/systemrescue-8.04-amd64.iso /mnt/cdrom
>>> mount: /mnt/cdrom: failed to setup loop device for
>>> /usr/install/iso/systemrescue-8.04-amd64.iso.
>>>
>>> Reverting d5fd456c88aba4fcf77d35fe38024a8d5c814686 fixes the problem:
>>>
>>> /tmp/util-linux-2.37# ./mount
>>> /usr/install/iso/systemrescue-8.04-amd64.iso /mnt/cdrom
>>> mount: /mnt/cdrom: WARNING: source write-protected, mounted read-only.
>>>
>>> I have not tested if 32 bit kernel + 32 bit userspace is also affected,
>>> but 64 bit kernel + 64 bit userspace works.
>>
>> Some debugging data:
>>
>> 30399: loopdev: CXT: [0xff8d0f98]: using loop-control
>> 30399: loopdev: CXT: [0xff8d0f98]: loop0 name assigned
>> 30399: loopdev: CXT: [0xff8d0f98]: find_unused by loop-control [rc=0]
>> 30399: libmount: LOOP: [0x57cbbcb0]: trying to use /dev/loop0
>> 30399: loopdev: CXT: [0xff8d0f98]: set backing file=/usr/install/iso/systemrescue-8.04-amd64.iso
>> 30399: loopdev: CXT: [0xff8d0f98]: set flags=4
>> 30399: loopdev: SETUP: [0xff8d0f98]: device setup requested
>> 30399: loopdev: SETUP: [0xff8d0f98]: backing file open: OK
>> 30399: loopdev: CXT: [0xff8d0f98]: open /dev/loop0 [rw]: Success
>> 30399: loopdev: SETUP: [0xff8d0f98]: device open: OK
>> 30399: loopdev: SETUP: [0xff8d0f98]: LOOP_CONFIGURE failed: Inappropriate ioctl for device
>> 30399: loopdev: SETUP: [0xff8d0f98]: failed [rc=-25]
>> 30399: libmount: LOOP: [0x57cbbcb0]: failed to setup device
>> 30399: loopdev: CXT: [0xff8d0f98]: de-initialize
>> 30399: loopdev: CXT: [0xff8d0f98]: closing old open fd
>> 30399: loopdev: ITER: [0xff8d1168]: de-initialize
>> 30399: libmount: CXT: [0x57cbbcb0]: mount: preparing failed
>> 30399: libmount: CXT: [0x57cbbcb0]: excode: rc=32 message="failed to setup loop device for /usr/install/iso/systemrescue-8.04-amd64.iso"
>> mount: /mnt/cdrom: failed to setup loop device for /usr/install/iso/systemrescue-8.04-amd64.iso.
>> 30399: libmount: CXT: [0x57cbbcb0]: <---- reset [status=0] ---->
>>
>> Seems like the code expects EINVAL (-22) but gets ENOTTY (-25), confirmed with strace:
>> ioctl(4, LOOP_CONFIGURE, {fd=3, block_size=0, info={lo_offset=0, lo_number=0, lo_flags=LO_FLAGS_AUTOCLEAR, lo_file_name="/usr/install/iso/systemrescue-8.04-amd64.iso", ...}}) = -1 ENOTTY (Inappropriate ioctl for device)
>>
>> Indeed, changing the code from:
>> if (errno != EINVAL)
>> to:
>> if (errno != EINVAL && errno != ENOTTY)
>> allows it to work.
>>
>> Not that with 64-bit userspace, kernel returns EINVAL:
>>
>> ioctl(4, LOOP_CONFIGURE, {fd=3, block_size=0, info={lo_offset=0, lo_number=0, lo_flags=LO_FLAGS_AUTOCLEAR, lo_file_name="/usr/src/PACKAGES/systemrescue-8.04-amd64.iso", ...}}) = -1 EINVAL (Invalid argument)
>
> ... which is because lo_compat_ioctl returns -ENOIOCTLCMD for
> unsupported cmds, while lo_ioctl returns -EINVAL via lo_simple_ioctl.
>
> And vfs_ioctl returns -ENOTTY for -ENOIOCTLCMD.
>
> Now the question is if this inconsistency is intended? :)
That's unfortunate, but probably not something that can get corrected at
this time. The correct return value for an unknown ioctl is -ENOTTY
(ENOIOCTLCMD isn't user visible, should get turned into that). But
current behavior is set in stone at this point, even if it is
technically incorrect.
--
Jens Axboe
On 2021-07-27 at 18:24, Jens Axboe wrote:
> On 7/27/21 4:56 PM, Krzysztof Olędzki wrote:
>> On 2021-07-27 at 15:39, Krzysztof Olędzki wrote:
>>> On 2021-07-27 at 14:53, Krzysztof Olędzki wrote:
>>>> Hi,
>>>>
>>>> I have a number of (older) systems that are still based on 32 bit
>>>> userspace but are running a relatively modern 64 bit kernel -
>>>> 5.4-stable, where BTW - LOOP_CONFIGURE is not yet available.
>>>>
>>>> I noticed that starting with util-linux-2.37 it is no longer possible to
>>>> mount images using loop:
>>>>
>>>> # mount /usr/install/iso/systemrescue-8.04-amd64.iso /mnt/cdrom
>>>> mount: /mnt/cdrom: failed to setup loop device for
>>>> /usr/install/iso/systemrescue-8.04-amd64.iso.
>>>>
>>>> Reverting d5fd456c88aba4fcf77d35fe38024a8d5c814686 fixes the problem:
>>>>
>>>> /tmp/util-linux-2.37# ./mount
>>>> /usr/install/iso/systemrescue-8.04-amd64.iso /mnt/cdrom
>>>> mount: /mnt/cdrom: WARNING: source write-protected, mounted read-only.
>>>>
>>>> I have not tested if 32 bit kernel + 32 bit userspace is also affected,
>>>> but 64 bit kernel + 64 bit userspace works.
>>>
>>> Some debugging data:
>>>
>>> 30399: loopdev: CXT: [0xff8d0f98]: using loop-control
>>> 30399: loopdev: CXT: [0xff8d0f98]: loop0 name assigned
>>> 30399: loopdev: CXT: [0xff8d0f98]: find_unused by loop-control [rc=0]
>>> 30399: libmount: LOOP: [0x57cbbcb0]: trying to use /dev/loop0
>>> 30399: loopdev: CXT: [0xff8d0f98]: set backing file=/usr/install/iso/systemrescue-8.04-amd64.iso
>>> 30399: loopdev: CXT: [0xff8d0f98]: set flags=4
>>> 30399: loopdev: SETUP: [0xff8d0f98]: device setup requested
>>> 30399: loopdev: SETUP: [0xff8d0f98]: backing file open: OK
>>> 30399: loopdev: CXT: [0xff8d0f98]: open /dev/loop0 [rw]: Success
>>> 30399: loopdev: SETUP: [0xff8d0f98]: device open: OK
>>> 30399: loopdev: SETUP: [0xff8d0f98]: LOOP_CONFIGURE failed: Inappropriate ioctl for device
>>> 30399: loopdev: SETUP: [0xff8d0f98]: failed [rc=-25]
>>> 30399: libmount: LOOP: [0x57cbbcb0]: failed to setup device
>>> 30399: loopdev: CXT: [0xff8d0f98]: de-initialize
>>> 30399: loopdev: CXT: [0xff8d0f98]: closing old open fd
>>> 30399: loopdev: ITER: [0xff8d1168]: de-initialize
>>> 30399: libmount: CXT: [0x57cbbcb0]: mount: preparing failed
>>> 30399: libmount: CXT: [0x57cbbcb0]: excode: rc=32 message="failed to setup loop device for /usr/install/iso/systemrescue-8.04-amd64.iso"
>>> mount: /mnt/cdrom: failed to setup loop device for /usr/install/iso/systemrescue-8.04-amd64.iso.
>>> 30399: libmount: CXT: [0x57cbbcb0]: <---- reset [status=0] ---->
>>>
>>> Seems like the code expects EINVAL (-22) but gets ENOTTY (-25), confirmed with strace:
>>> ioctl(4, LOOP_CONFIGURE, {fd=3, block_size=0, info={lo_offset=0, lo_number=0, lo_flags=LO_FLAGS_AUTOCLEAR, lo_file_name="/usr/install/iso/systemrescue-8.04-amd64.iso", ...}}) = -1 ENOTTY (Inappropriate ioctl for device)
>>>
>>> Indeed, changing the code from:
>>> if (errno != EINVAL)
>>> to:
>>> if (errno != EINVAL && errno != ENOTTY)
>>> allows it to work.
>>>
>>> Not that with 64-bit userspace, kernel returns EINVAL:
>>>
>>> ioctl(4, LOOP_CONFIGURE, {fd=3, block_size=0, info={lo_offset=0, lo_number=0, lo_flags=LO_FLAGS_AUTOCLEAR, lo_file_name="/usr/src/PACKAGES/systemrescue-8.04-amd64.iso", ...}}) = -1 EINVAL (Invalid argument)
>>
>> ... which is because lo_compat_ioctl returns -ENOIOCTLCMD for
>> unsupported cmds, while lo_ioctl returns -EINVAL via lo_simple_ioctl.
>>
>> And vfs_ioctl returns -ENOTTY for -ENOIOCTLCMD.
>>
>> Now the question is if this inconsistency is intended? :)
>
> That's unfortunate, but probably not something that can get corrected at
> this time. The correct return value for an unknown ioctl is -ENOTTY
> (ENOIOCTLCMD isn't user visible, should get turned into that).
Yes, it does - as I said, vfs_ioctl handles this properly. However, this
only works for .compat_ioctl (via mentioned lo_compat_ioctl which
returns -ENOIOCTLCMD) but not for .ioctl (via lo_ioctl, which returns
-EINVAL).
> But
> current behavior is set in stone at this point, even if it is
> technically incorrect.
Agreed. And even if this could be somehow fixed in further kernels, I
believe we still need to fix the userspace to support and properly
handle all the existing kernels.
So, to confirm - checking for both EINVAL and ENOTTY after
LOOP_CONFIGURE is the proper way of taking care this?
https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/tree/lib/loopdev.c?id=d4423cce9b9001c9de7ebc6f64f6cc2bb854944c#n1362
Thanks,
Krzysztof
On Tue, Jul 27, 2021 at 10:46:06PM -0700, Krzysztof Olędzki wrote:
> So, to confirm - checking for both EINVAL and ENOTTY after LOOP_CONFIGURE is
> the proper way of taking care this?
>
> https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/tree/lib/loopdev.c?id=d4423cce9b9001c9de7ebc6f64f6cc2bb854944c#n1362
We need both to make losetup/mount robust for already released kernels.
Fixed: https://github.com/karelzak/util-linux/commit/583990d25b5d65a9a9771a39d112de0ee16a1f3a
Thanks for your report!
Karel
--
Karel Zak <[email protected]>
http://karelzak.blogspot.com
Thanks for fixing the issue and making it more robust.