[PATCH 0/1] __asm_copy_to-from_user: Reduce more byte_copy

[Akira Tsukamoto]

Hi Qiu,

On 8/15/2021 11:30 AM, Qiu Wenbo wrote:
> Hi Akira,
> 
> 
> This patch breaks my userspace  and I can't boot my system after applying this. Here is the stack trace:
> 
> 
> [   10.349080] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> [   10.357116] Oops [#15]
> [   10.359433] CPU: 2 PID: 169 Comm: (networkd) Tainted: G D           5.14.0-rc5 #53
> [   10.367422] Hardware name: SiFive HiFive Unmatched A00 (DT)
> [   10.372981] epc : __asm_copy_from_user+0x48/0xf0
> [   10.377584]  ra : _copy_from_user+0x28/0x68
> [   10.381754] epc : ffffffff8099a280 ra : ffffffff803614a8 sp : ffffffd00416bd90
> [   10.388963]  gp : ffffffff811ee540 tp : ffffffe0841b3680 t0 : ffffffd00416bde0
> [   10.396172]  t1 : ffffffd00416bdd8 t2 : 0000003ff09ca3a0 s0 : ffffffd00416bdc0
> [   10.403381]  s1 : 0000000000000000 a0 : ffffffd00416bdd8 a1 : 0000000000000000
> [   10.410590]  a2 : 0000000000000010 a3 : 0000000000000040 a4 : ffffffd00416be18
> [   10.417800]  a5 : 0000003ffffffff0 a6 : 000000000000000f a7 : ffffffe085d58540
> [   10.425009]  s2 : 0000000000000010 s3 : ffffffd00416bdd8 s4 : 0000000000000002
> [   10.432218]  s5 : 0000000000000000 s6 : 0000000000000000 s7 : ffffffe0841b3680
> [   10.439427]  s8 : 0000002aad788040 s9 : 0000000000000000 s10: 0000000000000001
> [   10.446636]  s11: 0000000000000000 t3 : 0000000000000000 t4 : 0000000000000001
> [   10.453845]  t5 : 0000000000000010 t6 : 0000000000040000
> [   10.459144] status: 0000000200040120 badaddr: 0000000000000000 cause: 000000000000000d
> [   10.467049] [<ffffffff8099a280>] __asm_copy_from_user+0x48/0xf0
> [   10.472955] [<ffffffff8009a562>] do_seccomp+0x62/0x8be
> [   10.478079] [<ffffffff8009af58>] prctl_set_seccomp+0x24/0x32
> [   10.483725] [<ffffffff80020756>] sys_prctl+0xf6/0x450
> [   10.488763] [<ffffffff800034f2>] ret_from_syscall+0x0/0x2
> 
> 
> The PC register points to this line:
> 
> +1:
> +    REG_L    a5, 0(a1)

Thanks for testing! Do you mind teaching me how to reproduce the error?

Akira