* Re: [bug report] Bug: Write fault blocked by KUAP!
[not found] ` <CAFj5m9L8ahNYFf-tUAZFKAUzkeyqV-Sx94MxC268XJ-hqHPCig@mail.gmail.com>
@ 2026-02-26 12:44 ` Ming Lei
2026-02-26 16:59 ` Caleb Sander Mateos
0 siblings, 1 reply; 4+ messages in thread
From: Ming Lei @ 2026-02-26 12:44 UTC (permalink / raw)
To: Changhui Zhong, Caleb Sander Mateos
Cc: Linux Block Devices, Ming Lei, linuxppc-dev
On Thu, Feb 26, 2026 at 6:48 PM Ming Lei <ming.lei@redhat.com> wrote:
>
> Hi Changhui,
>
> Thanks for the report!
>
> Loop Caleb Sander Mateos in.
>
> Thanks,
>
> On Thu, Feb 26, 2026 at 6:37 PM Changhui Zhong <czhong@redhat.com> wrote:
> >
> > Hello,
> >
> > on the ppc64le arch, I hit the issue below with ublksrv on the latest
> > linux-block/for-next, please help check it, and let me know if you
> > need any info/test for it. Thanks.
> >
> > INFO: HEAD of cloned kernel
> > commit 37a43fd770f3dcac8f72f3ea909b3e893e2385c9
> > Merge: 13cd9b41227a c1dfbd7e71b0
> > Author: Jens Axboe <axboe@kernel.dk>
> > Date: Wed Feb 25 08:37:06 2026 -0700
> >
> > Merge branch 'for-7.1/block' into for-next
> >
> > * for-7.1/block:
> > ublk: report BLK_SPLIT_INTERVAL_CAPABLE
> >
> > reproducer:
> > compile and install https://github.com/ublk-org/ublksrv.git
> > #echo 0 > /proc/sys/kernel/io_uring_disabled
> > #modprobe ublk_drv
> > #cd ublksrv
> > #make test T=null
> > #make test T=loop
> >
> > dmesg log：
> > Feb 26 00:24:30 ibm-p9z-27-lp26 journal: running null/002
> > Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: start ublksrv io
> > daemon ublksrvd-0
> > Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: tid 57923: ublk dev
> > 0 queue 0 started
> > Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: tid 57924: ublk dev
> > 0 queue 1 started
> > Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > [1772083476.4882] platform-linux: do-add-ip6-address[2:
> > fe80::8448:a3ff:fe51:f102]: failure 13 (Permission denied - ipv6: IPv6
> > is disabled on this device)
> > Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > [1772083476.4885] platform-linux: do-add-ip6-address[2:
> > 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> > ipv6: IPv6 is disabled on this device)
> > Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > [1772083476.4938] l3cfg[0f1985ec14299e62,ifindex=2]: unable to
> > configure IPv6 route: type unicast fe80::/64 dev 2 metric 1024 mss 0
> > rt-src ipv6ll
> > Feb 26 00:24:38 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > [1772083478.4938] ipv6ll[95ab7f3fdbfe643d,ifindex=2]: changed: no IPv6
> > link local address to retry after Duplicate Address Detection failures
> > (back off)
> > Feb 26 00:24:38 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > [1772083478.4943] platform-linux: do-add-ip6-address[2:
> > 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> > ipv6: IPv6 is disabled on this device)
> > Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > [1772083488.5034] platform-linux: do-add-ip6-address[2:
> > fe80::8448:a3ff:fe51:f102]: failure 13 (Permission denied - ipv6: IPv6
> > is disabled on this device)
> > Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > [1772083488.5037] platform-linux: do-add-ip6-address[2:
> > 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> > ipv6: IPv6 is disabled on this device)
> > Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > [1772083488.5041] l3cfg[0f1985ec14299e62,ifindex=2]: unable to
> > configure IPv6 route: type unicast fe80::/64 dev 2 metric 1024 mss 0
> > rt-src ipv6ll
> > Feb 26 00:24:50 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > [1772083490.5034] ipv6ll[95ab7f3fdbfe643d,ifindex=2]: changed: no IPv6
> > link local address to retry after Duplicate Address Detection failures
> > (back off)
> > Feb 26 00:24:50 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > [1772083490.5039] platform-linux: do-add-ip6-address[2:
> > 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> > ipv6: IPv6 is disabled on this device)
> > Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: Kernel attempted to read user
> > page (7fff81210000) - exploit attempt? (uid: 0)
> > Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: ------------[ cut here ]------------
> > Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: Bug: Read fault blocked by KUAP!
> > Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: WARNING:
> > arch/powerpc/mm/fault.c:231 at bad_kernel_fault.isra.0+0xc8/0x2c0,
> > CPU#5: lt-ublk.null/57924
oops, it shouldn't be related with `ublk: report BLK_SPLIT_INTERVAL_CAPABLE`,
Perhaps one issue lies in the ppcle64 architecture code.
I will find one ppc box and try to reproduce this.
Thanks,
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [bug report] Bug: Write fault blocked by KUAP!
2026-02-26 12:44 ` [bug report] Bug: Write fault blocked by KUAP! Ming Lei
@ 2026-02-26 16:59 ` Caleb Sander Mateos
2026-02-26 18:57 ` Christophe Leroy (CS GROUP)
0 siblings, 1 reply; 4+ messages in thread
From: Caleb Sander Mateos @ 2026-02-26 16:59 UTC (permalink / raw)
To: Ming Lei; +Cc: Changhui Zhong, Linux Block Devices, linuxppc-dev
On Thu, Feb 26, 2026 at 4:44 AM Ming Lei <ming.lei@redhat.com> wrote:
>
> On Thu, Feb 26, 2026 at 6:48 PM Ming Lei <ming.lei@redhat.com> wrote:
> >
> > Hi Changhui,
> >
> > Thanks for the report!
> >
> > Loop Caleb Sander Mateos in.
> >
> > Thanks,
> >
> > On Thu, Feb 26, 2026 at 6:37 PM Changhui Zhong <czhong@redhat.com> wrote:
> > >
> > > Hello,
> > >
> > > on the ppc64le arch, I hit the issue below with ublksrv on the latest
> > > linux-block/for-next, please help check it, and let me know if you
> > > need any info/test for it. Thanks.
> > >
> > > INFO: HEAD of cloned kernel
> > > commit 37a43fd770f3dcac8f72f3ea909b3e893e2385c9
> > > Merge: 13cd9b41227a c1dfbd7e71b0
> > > Author: Jens Axboe <axboe@kernel.dk>
> > > Date: Wed Feb 25 08:37:06 2026 -0700
> > >
> > > Merge branch 'for-7.1/block' into for-next
> > >
> > > * for-7.1/block:
> > > ublk: report BLK_SPLIT_INTERVAL_CAPABLE
> > >
> > > reproducer:
> > > compile and install https://github.com/ublk-org/ublksrv.git
> > > #echo 0 > /proc/sys/kernel/io_uring_disabled
> > > #modprobe ublk_drv
> > > #cd ublksrv
> > > #make test T=null
> > > #make test T=loop
> > >
> > > dmesg log：
> > > Feb 26 00:24:30 ibm-p9z-27-lp26 journal: running null/002
> > > Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: start ublksrv io
> > > daemon ublksrvd-0
> > > Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: tid 57923: ublk dev
> > > 0 queue 0 started
> > > Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: tid 57924: ublk dev
> > > 0 queue 1 started
> > > Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > > [1772083476.4882] platform-linux: do-add-ip6-address[2:
> > > fe80::8448:a3ff:fe51:f102]: failure 13 (Permission denied - ipv6: IPv6
> > > is disabled on this device)
> > > Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > > [1772083476.4885] platform-linux: do-add-ip6-address[2:
> > > 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> > > ipv6: IPv6 is disabled on this device)
> > > Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > > [1772083476.4938] l3cfg[0f1985ec14299e62,ifindex=2]: unable to
> > > configure IPv6 route: type unicast fe80::/64 dev 2 metric 1024 mss 0
> > > rt-src ipv6ll
> > > Feb 26 00:24:38 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > > [1772083478.4938] ipv6ll[95ab7f3fdbfe643d,ifindex=2]: changed: no IPv6
> > > link local address to retry after Duplicate Address Detection failures
> > > (back off)
> > > Feb 26 00:24:38 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > > [1772083478.4943] platform-linux: do-add-ip6-address[2:
> > > 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> > > ipv6: IPv6 is disabled on this device)
> > > Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > > [1772083488.5034] platform-linux: do-add-ip6-address[2:
> > > fe80::8448:a3ff:fe51:f102]: failure 13 (Permission denied - ipv6: IPv6
> > > is disabled on this device)
> > > Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > > [1772083488.5037] platform-linux: do-add-ip6-address[2:
> > > 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> > > ipv6: IPv6 is disabled on this device)
> > > Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > > [1772083488.5041] l3cfg[0f1985ec14299e62,ifindex=2]: unable to
> > > configure IPv6 route: type unicast fe80::/64 dev 2 metric 1024 mss 0
> > > rt-src ipv6ll
> > > Feb 26 00:24:50 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > > [1772083490.5034] ipv6ll[95ab7f3fdbfe643d,ifindex=2]: changed: no IPv6
> > > link local address to retry after Duplicate Address Detection failures
> > > (back off)
> > > Feb 26 00:24:50 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> > > [1772083490.5039] platform-linux: do-add-ip6-address[2:
> > > 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> > > ipv6: IPv6 is disabled on this device)
> > > Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: Kernel attempted to read user
> > > page (7fff81210000) - exploit attempt? (uid: 0)
> > > Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: ------------[ cut here ]------------
> > > Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: Bug: Read fault blocked by KUAP!
> > > Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: WARNING:
> > > arch/powerpc/mm/fault.c:231 at bad_kernel_fault.isra.0+0xc8/0x2c0,
> > > CPU#5: lt-ublk.null/57924
>
> oops, it shouldn't be related with `ublk: report BLK_SPLIT_INTERVAL_CAPABLE`,
> Perhaps one issue lies in the ppcle64 architecture code.
Agreed, the "Kernel attempted to read user page" error seems
incorrect. The call trace shows this is in copy_from_iter(), so
reading a user page is expected. I too would be suspicious of the
powerpc copy_from_iter() implementation.
Best,
Caleb
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [bug report] Bug: Write fault blocked by KUAP!
2026-02-26 16:59 ` Caleb Sander Mateos
@ 2026-02-26 18:57 ` Christophe Leroy (CS GROUP)
2026-02-28 2:57 ` Changhui Zhong
0 siblings, 1 reply; 4+ messages in thread
From: Christophe Leroy (CS GROUP) @ 2026-02-26 18:57 UTC (permalink / raw)
To: Caleb Sander Mateos, Ming Lei
Cc: Changhui Zhong, Linux Block Devices, linuxppc-dev
Le 26/02/2026 à 17:59, Caleb Sander Mateos a écrit :
> On Thu, Feb 26, 2026 at 4:44 AM Ming Lei <ming.lei@redhat.com> wrote:
>>
>> On Thu, Feb 26, 2026 at 6:48 PM Ming Lei <ming.lei@redhat.com> wrote:
>>>
>>> Hi Changhui,
>>>
>>> Thanks for the report!
>>>
>>> Loop Caleb Sander Mateos in.
>>>
>>> Thanks,
>>>
>>> On Thu, Feb 26, 2026 at 6:37 PM Changhui Zhong <czhong@redhat.com> wrote:
>>>>
>>>> Hello,
>>>>
>>>> on the ppc64le arch, I hit the issue below with ublksrv on the latest
>>>> linux-block/for-next, please help check it, and let me know if you
>>>> need any info/test for it. Thanks.
>>>>
>>>> INFO: HEAD of cloned kernel
>>>> commit 37a43fd770f3dcac8f72f3ea909b3e893e2385c9
>>>> Merge: 13cd9b41227a c1dfbd7e71b0
>>>> Author: Jens Axboe <axboe@kernel.dk>
>>>> Date: Wed Feb 25 08:37:06 2026 -0700
>>>>
>>>> Merge branch 'for-7.1/block' into for-next
>>>>
>>>> * for-7.1/block:
>>>> ublk: report BLK_SPLIT_INTERVAL_CAPABLE
>>>>
>>>> reproducer:
>>>> compile and install https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fublk-org%2Fublksrv.git&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7Cf0b0066758be476be95508de75587a73%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639077220067774377%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=ki4yUMx%2FBTANcpfzEoVMdBKsuflIbzhHO2Wqpxtvj5g%3D&reserved=0
>>>> #echo 0 > /proc/sys/kernel/io_uring_disabled
>>>> #modprobe ublk_drv
>>>> #cd ublksrv
>>>> #make test T=null
>>>> #make test T=loop
>>>>
>>>> dmesg log：
>>>> Feb 26 00:24:30 ibm-p9z-27-lp26 journal: running null/002
>>>> Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: start ublksrv io
>>>> daemon ublksrvd-0
>>>> Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: tid 57923: ublk dev
>>>> 0 queue 0 started
>>>> Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: tid 57924: ublk dev
>>>> 0 queue 1 started
>>>> Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
>>>> [1772083476.4882] platform-linux: do-add-ip6-address[2:
>>>> fe80::8448:a3ff:fe51:f102]: failure 13 (Permission denied - ipv6: IPv6
>>>> is disabled on this device)
>>>> Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
>>>> [1772083476.4885] platform-linux: do-add-ip6-address[2:
>>>> 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
>>>> ipv6: IPv6 is disabled on this device)
>>>> Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
>>>> [1772083476.4938] l3cfg[0f1985ec14299e62,ifindex=2]: unable to
>>>> configure IPv6 route: type unicast fe80::/64 dev 2 metric 1024 mss 0
>>>> rt-src ipv6ll
>>>> Feb 26 00:24:38 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
>>>> [1772083478.4938] ipv6ll[95ab7f3fdbfe643d,ifindex=2]: changed: no IPv6
>>>> link local address to retry after Duplicate Address Detection failures
>>>> (back off)
>>>> Feb 26 00:24:38 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
>>>> [1772083478.4943] platform-linux: do-add-ip6-address[2:
>>>> 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
>>>> ipv6: IPv6 is disabled on this device)
>>>> Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
>>>> [1772083488.5034] platform-linux: do-add-ip6-address[2:
>>>> fe80::8448:a3ff:fe51:f102]: failure 13 (Permission denied - ipv6: IPv6
>>>> is disabled on this device)
>>>> Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
>>>> [1772083488.5037] platform-linux: do-add-ip6-address[2:
>>>> 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
>>>> ipv6: IPv6 is disabled on this device)
>>>> Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
>>>> [1772083488.5041] l3cfg[0f1985ec14299e62,ifindex=2]: unable to
>>>> configure IPv6 route: type unicast fe80::/64 dev 2 metric 1024 mss 0
>>>> rt-src ipv6ll
>>>> Feb 26 00:24:50 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
>>>> [1772083490.5034] ipv6ll[95ab7f3fdbfe643d,ifindex=2]: changed: no IPv6
>>>> link local address to retry after Duplicate Address Detection failures
>>>> (back off)
>>>> Feb 26 00:24:50 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
>>>> [1772083490.5039] platform-linux: do-add-ip6-address[2:
>>>> 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
>>>> ipv6: IPv6 is disabled on this device)
>>>> Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: Kernel attempted to read user
>>>> page (7fff81210000) - exploit attempt? (uid: 0)
>>>> Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: ------------[ cut here ]------------
>>>> Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: Bug: Read fault blocked by KUAP!
>>>> Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: WARNING:
>>>> arch/powerpc/mm/fault.c:231 at bad_kernel_fault.isra.0+0xc8/0x2c0,
>>>> CPU#5: lt-ublk.null/57924
>>
>> oops, it shouldn't be related with `ublk: report BLK_SPLIT_INTERVAL_CAPABLE`,
>> Perhaps one issue lies in the ppcle64 architecture code.
>
> Agreed, the "Kernel attempted to read user page" error seems
> incorrect. The call trace shows this is in copy_from_iter(), so
> reading a user page is expected. I too would be suspicious of the
> powerpc copy_from_iter() implementation.
Looks similar to:
https://lore.kernel.org/all/20260109064917.777587-2-sshegde@linux.ibm.com/
That fix was rejected, more acceptable fix here:
https://lore.kernel.org/all/20260217124457.89219-1-sayalip@linux.ibm.com/
Let us know if it fixes the issue for you.
Christophe
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [bug report] Bug: Write fault blocked by KUAP!
2026-02-26 18:57 ` Christophe Leroy (CS GROUP)
@ 2026-02-28 2:57 ` Changhui Zhong
0 siblings, 0 replies; 4+ messages in thread
From: Changhui Zhong @ 2026-02-28 2:57 UTC (permalink / raw)
To: Christophe Leroy (CS GROUP)
Cc: Caleb Sander Mateos, Ming Lei, Linux Block Devices, linuxppc-dev
On Fri, Feb 27, 2026 at 3:05 AM Christophe Leroy (CS GROUP)
<chleroy@kernel.org> wrote:
>
>
>
> Le 26/02/2026 à 17:59, Caleb Sander Mateos a écrit :
> > On Thu, Feb 26, 2026 at 4:44 AM Ming Lei <ming.lei@redhat.com> wrote:
> >>
> >> On Thu, Feb 26, 2026 at 6:48 PM Ming Lei <ming.lei@redhat.com> wrote:
> >>>
> >>> Hi Changhui,
> >>>
> >>> Thanks for the report!
> >>>
> >>> Loop Caleb Sander Mateos in.
> >>>
> >>> Thanks,
> >>>
> >>> On Thu, Feb 26, 2026 at 6:37 PM Changhui Zhong <czhong@redhat.com> wrote:
> >>>>
> >>>> Hello,
> >>>>
> >>>> on the ppc64le arch, I hit the issue below with ublksrv on the latest
> >>>> linux-block/for-next, please help check it, and let me know if you
> >>>> need any info/test for it. Thanks.
> >>>>
> >>>> INFO: HEAD of cloned kernel
> >>>> commit 37a43fd770f3dcac8f72f3ea909b3e893e2385c9
> >>>> Merge: 13cd9b41227a c1dfbd7e71b0
> >>>> Author: Jens Axboe <axboe@kernel.dk>
> >>>> Date: Wed Feb 25 08:37:06 2026 -0700
> >>>>
> >>>> Merge branch 'for-7.1/block' into for-next
> >>>>
> >>>> * for-7.1/block:
> >>>> ublk: report BLK_SPLIT_INTERVAL_CAPABLE
> >>>>
> >>>> reproducer:
> >>>> compile and install https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fublk-org%2Fublksrv.git&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7Cf0b0066758be476be95508de75587a73%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639077220067774377%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=ki4yUMx%2FBTANcpfzEoVMdBKsuflIbzhHO2Wqpxtvj5g%3D&reserved=0
> >>>> #echo 0 > /proc/sys/kernel/io_uring_disabled
> >>>> #modprobe ublk_drv
> >>>> #cd ublksrv
> >>>> #make test T=null
> >>>> #make test T=loop
> >>>>
> >>>> dmesg log：
> >>>> Feb 26 00:24:30 ibm-p9z-27-lp26 journal: running null/002
> >>>> Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: start ublksrv io
> >>>> daemon ublksrvd-0
> >>>> Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: tid 57923: ublk dev
> >>>> 0 queue 0 started
> >>>> Feb 26 00:24:30 ibm-p9z-27-lp26 ublksrvd-0[57921]: tid 57924: ublk dev
> >>>> 0 queue 1 started
> >>>> Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> >>>> [1772083476.4882] platform-linux: do-add-ip6-address[2:
> >>>> fe80::8448:a3ff:fe51:f102]: failure 13 (Permission denied - ipv6: IPv6
> >>>> is disabled on this device)
> >>>> Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> >>>> [1772083476.4885] platform-linux: do-add-ip6-address[2:
> >>>> 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> >>>> ipv6: IPv6 is disabled on this device)
> >>>> Feb 26 00:24:36 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> >>>> [1772083476.4938] l3cfg[0f1985ec14299e62,ifindex=2]: unable to
> >>>> configure IPv6 route: type unicast fe80::/64 dev 2 metric 1024 mss 0
> >>>> rt-src ipv6ll
> >>>> Feb 26 00:24:38 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> >>>> [1772083478.4938] ipv6ll[95ab7f3fdbfe643d,ifindex=2]: changed: no IPv6
> >>>> link local address to retry after Duplicate Address Detection failures
> >>>> (back off)
> >>>> Feb 26 00:24:38 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> >>>> [1772083478.4943] platform-linux: do-add-ip6-address[2:
> >>>> 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> >>>> ipv6: IPv6 is disabled on this device)
> >>>> Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> >>>> [1772083488.5034] platform-linux: do-add-ip6-address[2:
> >>>> fe80::8448:a3ff:fe51:f102]: failure 13 (Permission denied - ipv6: IPv6
> >>>> is disabled on this device)
> >>>> Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> >>>> [1772083488.5037] platform-linux: do-add-ip6-address[2:
> >>>> 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> >>>> ipv6: IPv6 is disabled on this device)
> >>>> Feb 26 00:24:48 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> >>>> [1772083488.5041] l3cfg[0f1985ec14299e62,ifindex=2]: unable to
> >>>> configure IPv6 route: type unicast fe80::/64 dev 2 metric 1024 mss 0
> >>>> rt-src ipv6ll
> >>>> Feb 26 00:24:50 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> >>>> [1772083490.5034] ipv6ll[95ab7f3fdbfe643d,ifindex=2]: changed: no IPv6
> >>>> link local address to retry after Duplicate Address Detection failures
> >>>> (back off)
> >>>> Feb 26 00:24:50 ibm-p9z-27-lp26 NetworkManager[818]: <warn>
> >>>> [1772083490.5039] platform-linux: do-add-ip6-address[2:
> >>>> 2620:52:9:160c:8448:a3ff:fe51:f102]: failure 13 (Permission denied -
> >>>> ipv6: IPv6 is disabled on this device)
> >>>> Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: Kernel attempted to read user
> >>>> page (7fff81210000) - exploit attempt? (uid: 0)
> >>>> Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: ------------[ cut here ]------------
> >>>> Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: Bug: Read fault blocked by KUAP!
> >>>> Feb 26 00:24:58 ibm-p9z-27-lp26 kernel: WARNING:
> >>>> arch/powerpc/mm/fault.c:231 at bad_kernel_fault.isra.0+0xc8/0x2c0,
> >>>> CPU#5: lt-ublk.null/57924
> >>
> >> oops, it shouldn't be related with `ublk: report BLK_SPLIT_INTERVAL_CAPABLE`,
> >> Perhaps one issue lies in the ppcle64 architecture code.
> >
> > Agreed, the "Kernel attempted to read user page" error seems
> > incorrect. The call trace shows this is in copy_from_iter(), so
> > reading a user page is expected. I too would be suspicious of the
> > powerpc copy_from_iter() implementation.
>
> Looks similar to:
>
> https://lore.kernel.org/all/20260109064917.777587-2-sshegde@linux.ibm.com/
>
> That fix was rejected, more acceptable fix here:
>
> https://lore.kernel.org/all/20260217124457.89219-1-sayalip@linux.ibm.com/
>
> Let us know if it fixes the issue for you.
>
> Christophe
>
Hi， Christophe
confirmed that after applying the patch
https://lore.kernel.org/all/20260217124457.89219-1-sayalip@linux.ibm.com/,
this issue has not been hit again, the fix works.
Thanks,
Changhui
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2026-02-26 12:44 ` [bug report] Bug: Write fault blocked by KUAP! Ming Lei
2026-02-26 16:59 ` Caleb Sander Mateos
2026-02-26 18:57 ` Christophe Leroy (CS GROUP)
2026-02-28 2:57 ` Changhui Zhong
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