From: Andreas Schwab <schwab@linux-m68k.org>
To: Jisheng Zhang <jszhang3@mail.ustc.edu.cn>
Cc: "Paul Walmsley" <paul.walmsley@sifive.com>,
"Palmer Dabbelt" <palmer@dabbelt.com>,
"Albert Ou" <aou@eecs.berkeley.edu>,
"Andrey Ryabinin" <ryabinin.a.a@gmail.com>,
"Alexander Potapenko" <glider@google.com>,
"Andrey Konovalov" <andreyknvl@gmail.com>,
"Dmitry Vyukov" <dvyukov@google.com>,
"Björn Töpel" <bjorn@kernel.org>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
"John Fastabend" <john.fastabend@gmail.com>,
"KP Singh" <kpsingh@kernel.org>,
"Luke Nelson" <luke.r.nels@gmail.com>,
"Xi Wang" <xi.wang@gmail.com>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
kasan-dev@googlegroups.com, netdev@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [PATCH 7/9] riscv: bpf: Avoid breaking W^X
Date: Sun, 13 Jun 2021 21:50:53 +0200 [thread overview]
Message-ID: <87im2hsfvm.fsf@igel.home> (raw)
In-Reply-To: <20210614010546.7a0d5584@xhacker> (Jisheng Zhang's message of "Mon, 14 Jun 2021 01:05:46 +0800")
On Jun 14 2021, Jisheng Zhang wrote:
> I think I found the root cause: commit 2bfc6cd81bd ("move kernel mapping
> outside of linear mapping") moves BPF JIT region after the kernel:
>
> #define BPF_JIT_REGION_START PFN_ALIGN((unsigned long)&_end)
>
> The &_end is unlikely aligned with PMD SIZE, so the front bpf jit region
> sits with kernel .data section in one PMD. But kenrel is mapped in PMD SIZE,
> so when bpf_jit_binary_lock_ro() is called to make the first bpf jit prog
> ROX, we will make part of kernel .data section RO too, so when we write, for example
> memset the .data section, MMU will trigger store page fault.
>
> To fix the issue, we need to make the bpf jit region PMD size aligned by either
> patch BPF_JIT_REGION_START to align on PMD size rather than PAGE SIZE, or
> something as below patch to move the BPF region before modules region:
>
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 9469f464e71a..997b894edbc2 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -31,8 +31,8 @@
> #define BPF_JIT_REGION_SIZE (SZ_128M)
> #ifdef CONFIG_64BIT
> /* KASLR should leave at least 128MB for BPF after the kernel */
> -#define BPF_JIT_REGION_START PFN_ALIGN((unsigned long)&_end)
> -#define BPF_JIT_REGION_END (BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE)
> +#define BPF_JIT_REGION_START (BPF_JIT_REGION_END - BPF_JIT_REGION_SIZE)
> +#define BPF_JIT_REGION_END (MODULES_VADDR)
> #else
> #define BPF_JIT_REGION_START (PAGE_OFFSET - BPF_JIT_REGION_SIZE)
> #define BPF_JIT_REGION_END (VMALLOC_END)
> @@ -40,8 +40,8 @@
>
> /* Modules always live before the kernel */
> #ifdef CONFIG_64BIT
> -#define MODULES_VADDR (PFN_ALIGN((unsigned long)&_end) - SZ_2G)
> #define MODULES_END (PFN_ALIGN((unsigned long)&_start))
> +#define MODULES_VADDR (MODULES_END - SZ_128M)
> #endif
>
>
> can you please try it? Per my test, the issue is fixed.
I can confirm that this fixes the issue.
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
next prev parent reply other threads:[~2021-06-13 19:51 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-29 18:21 [PATCH 0/9] riscv: improve self-protection Jisheng Zhang
2021-03-29 18:22 ` [PATCH 1/9] riscv: add __init section marker to some functions Jisheng Zhang
2021-03-29 18:22 ` [PATCH 2/9] riscv: Mark some global variables __ro_after_init Jisheng Zhang
2021-03-29 18:23 ` [PATCH 3/9] riscv: Constify sys_call_table Jisheng Zhang
2021-03-29 18:23 ` [PATCH 4/9] riscv: Constify sbi_ipi_ops Jisheng Zhang
2021-03-29 18:24 ` [PATCH 5/9] riscv: kprobes: Implement alloc_insn_page() Jisheng Zhang
2021-03-29 18:24 ` [PATCH 6/9] riscv: bpf: Move bpf_jit_alloc_exec() and bpf_jit_free_exec() to core Jisheng Zhang
2021-03-29 20:41 ` Luke Nelson
2021-03-29 18:25 ` [PATCH 7/9] riscv: bpf: Avoid breaking W^X Jisheng Zhang
2021-06-11 14:10 ` Andreas Schwab
2021-06-11 16:23 ` Jisheng Zhang
2021-06-11 16:41 ` Andreas Schwab
2021-06-13 17:05 ` Jisheng Zhang
2021-06-13 19:50 ` Andreas Schwab [this message]
2021-06-14 16:49 ` [PATCH] riscv: Ensure BPF_JIT_REGION_START aligned with PMD size Jisheng Zhang
2021-06-15 12:29 ` Daniel Borkmann
2021-06-15 18:54 ` Alex Ghiti
2021-06-16 0:03 ` Jisheng Zhang
2021-06-17 7:23 ` Alex Ghiti
2021-06-17 17:17 ` Jisheng Zhang
2021-06-17 7:30 ` Palmer Dabbelt
2021-06-17 8:09 ` Alex Ghiti
2021-06-17 14:18 ` Alex Ghiti
2021-06-17 17:27 ` Jisheng Zhang
2021-06-17 17:46 ` Jisheng Zhang
2021-06-17 18:10 ` Jisheng Zhang
2021-06-17 18:15 ` [PATCH v2] " Jisheng Zhang
2021-06-18 6:48 ` Alex Ghiti
2021-03-29 18:25 ` [PATCH 8/9] riscv: module: Create module allocations without exec permissions Jisheng Zhang
2021-03-29 18:26 ` [PATCH 9/9] riscv: Set ARCH_HAS_STRICT_MODULE_RWX if MMU Jisheng Zhang
2021-04-23 1:48 ` [PATCH 0/9] riscv: improve self-protection Palmer Dabbelt
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