* Re: Commit d5fd456c88aba4fcf77d35fe38024a8d5c814686 - "loopdev: use LOOP_CONFIG ioctl" broke loop on x86-64 w/ 32 bit userspace [not found] ` <e7f64d43-2a26-e386-b208-5c35d6a56ed4@ans.pl> @ 2021-07-27 22:56 ` Krzysztof Olędzki 2021-07-28 1:24 ` Jens Axboe 0 siblings, 1 reply; 5+ messages in thread From: Krzysztof Olędzki @ 2021-07-27 22:56 UTC (permalink / raw) To: Sinan Kaya, Karel Zak, Jens Axboe Cc: util-linux, linux-block, Linux Kernel Mailing List 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Commit d5fd456c88aba4fcf77d35fe38024a8d5c814686 - "loopdev: use LOOP_CONFIG ioctl" broke loop on x86-64 w/ 32 bit userspace 2021-07-27 22:56 ` Commit d5fd456c88aba4fcf77d35fe38024a8d5c814686 - "loopdev: use LOOP_CONFIG ioctl" broke loop on x86-64 w/ 32 bit userspace Krzysztof Olędzki @ 2021-07-28 1:24 ` Jens Axboe 2021-07-28 5:46 ` Krzysztof Olędzki 0 siblings, 1 reply; 5+ messages in thread From: Jens Axboe @ 2021-07-28 1:24 UTC (permalink / raw) To: Krzysztof Olędzki, Sinan Kaya, Karel Zak Cc: util-linux, linux-block, Linux Kernel Mailing List 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Commit d5fd456c88aba4fcf77d35fe38024a8d5c814686 - "loopdev: use LOOP_CONFIG ioctl" broke loop on x86-64 w/ 32 bit userspace 2021-07-28 1:24 ` Jens Axboe @ 2021-07-28 5:46 ` Krzysztof Olędzki 2021-07-28 9:14 ` Karel Zak 0 siblings, 1 reply; 5+ messages in thread From: Krzysztof Olędzki @ 2021-07-28 5:46 UTC (permalink / raw) To: Jens Axboe, Sinan Kaya, Karel Zak Cc: util-linux, linux-block, Linux Kernel Mailing List 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Commit d5fd456c88aba4fcf77d35fe38024a8d5c814686 - "loopdev: use LOOP_CONFIG ioctl" broke loop on x86-64 w/ 32 bit userspace 2021-07-28 5:46 ` Krzysztof Olędzki @ 2021-07-28 9:14 ` Karel Zak 2021-07-28 18:00 ` Sinan Kaya 0 siblings, 1 reply; 5+ messages in thread From: Karel Zak @ 2021-07-28 9:14 UTC (permalink / raw) To: Krzysztof Olędzki Cc: Jens Axboe, Sinan Kaya, util-linux, linux-block, Linux Kernel Mailing List 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 <kzak@redhat.com> http://karelzak.blogspot.com ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Commit d5fd456c88aba4fcf77d35fe38024a8d5c814686 - "loopdev: use LOOP_CONFIG ioctl" broke loop on x86-64 w/ 32 bit userspace 2021-07-28 9:14 ` Karel Zak @ 2021-07-28 18:00 ` Sinan Kaya 0 siblings, 0 replies; 5+ messages in thread From: Sinan Kaya @ 2021-07-28 18:00 UTC (permalink / raw) To: Karel Zak, Krzysztof Olędzki Cc: Jens Axboe, util-linux, linux-block, Linux Kernel Mailing List Thanks for fixing the issue and making it more robust. ^ permalink raw reply [flat|nested] 5+ messages in thread
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[not found] ` <e7f64d43-2a26-e386-b208-5c35d6a56ed4@ans.pl>
2021-07-27 22:56 ` Commit d5fd456c88aba4fcf77d35fe38024a8d5c814686 - "loopdev: use LOOP_CONFIG ioctl" broke loop on x86-64 w/ 32 bit userspace Krzysztof Olędzki
2021-07-28 1:24 ` Jens Axboe
2021-07-28 5:46 ` Krzysztof Olędzki
2021-07-28 9:14 ` Karel Zak
2021-07-28 18:00 ` Sinan Kaya
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