On 09/02/2023 19:22, Anna Schumaker wrote: > Hi Krzysztof, > > On Mon, Jan 23, 2023 at 2:58 AM Krzysztof Kozlowski > <krzysztof.kozlowski@xxxxxxxxxx> wrote: >> >> On 22/01/2023 23:25, Anna Schumaker wrote: >>> Hi Krzysztof, >>> >>> On Mon, Jan 9, 2023 at 3:46 AM Krzysztof Kozlowski >>> <krzysztof.kozlowski@xxxxxxxxxx> wrote: >>>> >>>> On 09/01/2023 09:14, Krzysztof Kozlowski wrote: >>>>> On 08/01/2023 18:09, Trond Myklebust wrote: >>>>>> Hi Krzysztof, >>>>>> >>>>>>> On Jan 8, 2023, at 08:25, Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> wrote: >>>>>>> >>>>>>> [You don't often get email from krzysztof.kozlowski@xxxxxxxxxx. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification] >>>>>>> >>>>>>> On 07/01/2023 16:44, Krzysztof Kozlowski wrote: >>>>>>>> Hi, >>>>>>>> >>>>>>>> Bisect identified commit 7fd461c47c6c ("NFSv4.2: Change the default >>>>>>>> KConfig value for READ_PLUS") as one leading to NULL pointer exception >>>>>>>> when mounting NFS root on NFSv4 client: >>>>>>>> >>>>>>>> [ 25.739003] systemd[1]: Set hostname to <odroidhc1>. >>>>>>>> [ 25.771714] systemd[1]: Failed to bump fs.file-max, ignoring: Invalid >>>>>>>> argument >>>>>>>> [ 26.199478] 8<--- cut here --- >>>>>>>> [ 26.201366] Unable to handle kernel NULL pointer dereference at >>>>>>>> virtual address 00000004 >>>>>>>> ... >>>>>>>> [ 26.555522] mmiocpy from xdr_inline_decode+0xec/0x16c >>>>>>>> [ 26.560628] xdr_inline_decode from nfs4_xdr_dec_read_plus+0x178/0x358 >>>>>>>> [ 26.567130] nfs4_xdr_dec_read_plus from call_decode+0x204/0x304 >>>>>>>> >>>>>>>> Full OOPS attached. Full log available here: >>>>>>>> https://krzk.eu/#/builders/21/builds/3901/steps/15/logs/serial0 >>>>>>>> >>>>>>>> Disabling NFS_V4_2_READ_PLUS fixes the issue, so obviously the commit is >>>>>>>> not the cause, but rather making it default caused the regression. >>>>>>>> >>>>>>>> I did not make the bisect yet which commit introduced it, if every >>>>>>>> config includes NFS_V4_2_READ_PLUS. >>>>>>> >>>>>>> When every kernel is built with NFS_V4_2_READ_PLUS, bisect pointed to: >>>>>>> d3b00a802c84 ("NFS: Replace the READ_PLUS decoding code") >>>>>>> >>>>>>> commit d3b00a802c845a6021148ce2e669b5a0b5729959 >>>>>>> Author: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx> >>>>>>> Date: Thu Jul 21 14:21:34 2022 -0400 >>>>>>> >>>>>>> NFS: Replace the READ_PLUS decoding code >>>>>>> >>>>>>> We now take a 2-step process that allows us to place data and hole >>>>>>> segments directly at their final position in the xdr_stream without >>>>>>> needing to do a bunch of redundant copies to expand holes. Due to the >>>>>>> variable lengths of each segment, the xdr metadata might cross page >>>>>>> boundaries which I account for by setting a small scratch buffer so >>>>>>> xdr_inline_decode() won't fail. >>>>>>> >>>>>>> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx> >>>>>>> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> >>>>>>> >>>>>>> With a trace: >>>>>>> [ 25.898462] systemd[1]: Set hostname to <odroidhc1>. >>>>>>> [ 25.933746] systemd[1]: Failed to bump fs.file-max, ignoring: Invalid >>>>>>> argument >>>>>>> [ 25.986237] random: crng init done >>>>>>> [ 26.264564] 8<--- cut here --- >>>>>>> [ 26.266823] Unable to handle kernel NULL pointer dereference at >>>>>>> virtual address 00000fe8 >>>>>>> ... >>>>>>> [ 26.597263] nfs4_xdr_dec_read_plus from call_decode+0x204/0x304 >>>>>>> [ 26.603222] call_decode from __rpc_execute+0xd0/0x890 >>>>>>> [ 26.608328] __rpc_execute from rpc_async_schedule+0x1c/0x34 >>>>>>> [ 26.613960] rpc_async_schedule from process_one_work+0x294/0x790 >>>>>>> [ 26.620030] process_one_work from worker_thread+0x54/0x518 >>>>>>> [ 26.625570] worker_thread from kthread+0xf4/0x128 >>>>>>> [ 26.630336] kthread from ret_from_fork+0x14/0x2c >>>>>>> >>>>>> >>>>>> Is this test being run against a 6.2-rc2 server, or is it an older server platform? We know there were bugs in older server implementations, so the question is whether this might be a problem with handling a bad/corrupt RPC reply from the server, or whether it is happening against code that is supposed to have been fixed? >>>>> >>>>> I would say that buggy server should not cause NULL pointer dereferences >>>>> on the client. Otherwise this is a perfect recipe for a rogue server in >>>>> the network to start crashing clients and running exploits... Imagine a >>>>> compromised machine (through some other means) in a local company >>>>> network running now a server with NFS share "HR salary data" or "HR >>>>> planned layoffs", where unsuspected people in that network access it >>>>> leading to exploit of NFS code on their side... >>>>> >>>>> Server is Raspberry Pi 3 kernel: 5.10.92-2-rpi-legacy-ARCH >>>>> >>>>> Which points that it is not latest stable, so anyway I need to update. >>>> >>>> I updated the kernel to 5.15.84-3-rpi-ARCH which is pretty close to >>>> latest stable and I can reproduce the issue. Therefore: >>>> 1. It is visible on two stable (one new, one old) kernels on the server, >>>> 2. Buggy or rogue server should not cause NULL pointer on remote devices... >>> >>> I'm still working on this issue, but I haven't been able to reproduce >>> it with my setup at all yet. I was hoping I could ask you a couple of >>> questions? >>> >>> - Are both client and server run on a Raspberry Pi 3? >> >> No, server is Rpi3, client is Odroid HC1. >> >>> - Is there a specific workload that triggers the bug, or is it just >>> during boot when using nfsroot? >> >> No specific workload - mounting system with nfsroot. You have there full >> logs as it is reproducible every time. >> >>> - Would it be possible to get a Wireshark network trace of the crash >>> (you'll have to run this on the server due to nfsroot). >> >> I'll check. > > Any luck getting the wireshark trace? I don't have access to the > Odroid HC1 board, so all my attempts at reproducing the problem have > been with qemu & libvirt, which doesn't seem to be hitting this issue. I'll send pcap dump off list. Failure is in similar place: [ 23.876714] systemd[1]: Hostname set to <odroidhc1>. [ 24.061568] systemd[1]: bpf-lsm: BPF LSM hook not enabled in the kernel, BPF LSM not supported [ 24.078774] memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL, pid=1 'systemd' [ 24.220531] 8<--- cut here --- [ 24.222333] Unable to handle kernel NULL pointer dereference at virtual address 00000004 when read > > I was also wondering if it would be possible to turn on KASAN in your > kernel, which should give us a little more info? I'll try with KASAN. Best regards, Krzysztof
