netdev - Re: [PATCH v3 for-next 2/3] net: copy from user before calling __get_compat

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Date:   Fri, 15 Jul 2022 14:37:55 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Dylan Yudaken <dylany@...com>,
        Pavel Begunkov <asml.silence@...il.com>, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        io-uring@...r.kernel.org
Cc:     netdev@...r.kernel.org, Kernel-team@...com
Subject: Re: [PATCH v3 for-next 2/3] net: copy from user before calling
 __get_compat_msghdr

On 7/15/22 2:28 PM, Marek Szyprowski wrote:
> Hi,
> 
> On 14.07.2022 13:02, Dylan Yudaken wrote:
>> this is in preparation for multishot receive from io_uring, where it needs
>> to have access to the original struct user_msghdr.
>>
>> functionally this should be a no-op.
>>
>> Acked-by: Paolo Abeni <pabeni@...hat.com>
>> Signed-off-by: Dylan Yudaken <dylany@...com>
> 
> This patch landed in linux next-20220715 as commit 1a3e4e94a1b9 ("net: 
> copy from user before calling __get_compat_msghdr"). Unfortunately it 
> causes a serious regression on the ARM64 based Khadas VIM3l board:
> 
> Unable to handle kernel access to user memory outside uaccess routines 
> at virtual address 00000000ffc4a5c8
> Mem abort info:
>    ESR = 0x000000009600000f
>    EC = 0x25: DABT (current EL), IL = 32 bits
>    SET = 0, FnV = 0
>    EA = 0, S1PTW = 0
>    FSC = 0x0f: level 3 permission fault
> Data abort info:
>    ISV = 0, ISS = 0x0000000f
>    CM = 0, WnR = 0
> user pgtable: 4k pages, 48-bit VAs, pgdp=0000000001909000
> [00000000ffc4a5c8] pgd=0800000001a7b003, p4d=0800000001a7b003, 
> pud=0800000001a0e003, pmd=0800000001913003, pte=00e800000b9baf43
> Internal error: Oops: 9600000f [#1] PREEMPT SMP
> Modules linked in:
> CPU: 0 PID: 247 Comm: systemd-udevd Not tainted 5.19.0-rc6+ #12437
> Hardware name: Khadas VIM3L (DT)
> pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : get_compat_msghdr+0xd0/0x1b0
> lr : get_compat_msghdr+0xcc/0x1b0
> ...
> Call trace:
>   get_compat_msghdr+0xd0/0x1b0
>   ___sys_sendmsg+0xd0/0xe0
>   __sys_sendmsg+0x68/0xc4
>   __arm64_compat_sys_sendmsg+0x28/0x3c
>   invoke_syscall+0x48/0x114
>   el0_svc_common.constprop.0+0x60/0x11c
>   do_el0_svc_compat+0x1c/0x50
>   el0_svc_compat+0x58/0x100
>   el0t_32_sync_handler+0x90/0x140
>   el0t_32_sync+0x190/0x194
> Code: d2800382 9100f3e0 97d9be02 b5fffd60 (b9401a60)
> ---[ end trace 0000000000000000 ]---
> 
> This happens only on the mentioned board, other my ARM64 test boards 
> boot fine with next-20220715. Reverting this commit, together with 
> 2b0b67d55f13 ("fix up for "io_uring: support multishot in recvmsg"") and 
> a8b38c4ce724 ("io_uring: support multishot in recvmsg") due to compile 
> dependencies on top of next-20220715 fixes the issue.
> 
> Let me know how I can help fixing this issue.

How are you reproducing this?

-- 
Jens Axboe