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From: Jisheng Zhang <jszhang3@mail.ustc.edu.cn>
To: Andreas Schwab <schwab@linux-m68k.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>
Cc: "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: [PATCH] riscv: Ensure BPF_JIT_REGION_START aligned with PMD size
Date: Tue, 15 Jun 2021 00:49:27 +0800	[thread overview]
Message-ID: <20210615004928.2d27d2ac@xhacker> (raw)
In-Reply-To: <87im2hsfvm.fsf@igel.home>

From: Jisheng Zhang <jszhang@kernel.org>

Andreas reported commit fc8504765ec5 ("riscv: bpf: Avoid breaking W^X")
breaks booting with one kind of config file, I reproduced a kernel panic
with the config:

[    0.138553] Unable to handle kernel paging request at virtual address ffffffff81201220
[    0.139159] Oops [#1]
[    0.139303] Modules linked in:
[    0.139601] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-rc5-default+ #1
[    0.139934] Hardware name: riscv-virtio,qemu (DT)
[    0.140193] epc : __memset+0xc4/0xfc
[    0.140416]  ra : skb_flow_dissector_init+0x1e/0x82
[    0.140609] epc : ffffffff8029806c ra : ffffffff8033be78 sp : ffffffe001647da0
[    0.140878]  gp : ffffffff81134b08 tp : ffffffe001654380 t0 : ffffffff81201158
[    0.141156]  t1 : 0000000000000002 t2 : 0000000000000154 s0 : ffffffe001647dd0
[    0.141424]  s1 : ffffffff80a43250 a0 : ffffffff81201220 a1 : 0000000000000000
[    0.141654]  a2 : 000000000000003c a3 : ffffffff81201258 a4 : 0000000000000064
[    0.141893]  a5 : ffffffff8029806c a6 : 0000000000000040 a7 : ffffffffffffffff
[    0.142126]  s2 : ffffffff81201220 s3 : 0000000000000009 s4 : ffffffff81135088
[    0.142353]  s5 : ffffffff81135038 s6 : ffffffff8080ce80 s7 : ffffffff80800438
[    0.142584]  s8 : ffffffff80bc6578 s9 : 0000000000000008 s10: ffffffff806000ac
[    0.142810]  s11: 0000000000000000 t3 : fffffffffffffffc t4 : 0000000000000000
[    0.143042]  t5 : 0000000000000155 t6 : 00000000000003ff
[    0.143220] status: 0000000000000120 badaddr: ffffffff81201220 cause: 000000000000000f
[    0.143560] [<ffffffff8029806c>] __memset+0xc4/0xfc
[    0.143859] [<ffffffff8061e984>] init_default_flow_dissectors+0x22/0x60
[    0.144092] [<ffffffff800010fc>] do_one_initcall+0x3e/0x168
[    0.144278] [<ffffffff80600df0>] kernel_init_freeable+0x1c8/0x224
[    0.144479] [<ffffffff804868a8>] kernel_init+0x12/0x110
[    0.144658] [<ffffffff800022de>] ret_from_exception+0x0/0xc
[    0.145124] ---[ end trace f1e9643daa46d591 ]---

After some investigation, I think I found the root cause: commit
2bfc6cd81bd ("move kernel mapping outside of linear mapping") moves
BPF JIT region after the kernel:

The &_end is unlikely aligned with PMD size, so the front bpf jit
region sits with part of kernel .data section in one PMD size mapping.
But kernel is mapped in PMD SIZE, 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 to, for example memset the
.data section, MMU will trigger a store page fault.

To fix the issue, we need to ensure the BPF JIT region is PMD size
aligned. This patch acchieve this goal by restoring the BPF JIT region
to original position, I.E the 128MB before kernel .text section.

Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 arch/riscv/include/asm/pgtable.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 9469f464e71a..380cd3a7e548 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -30,9 +30,8 @@
 
 #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_END)
 #else
 #define BPF_JIT_REGION_START	(PAGE_OFFSET - BPF_JIT_REGION_SIZE)
 #define BPF_JIT_REGION_END	(VMALLOC_END)
-- 
2.32.0



WARNING: multiple messages have this Message-ID (diff)
From: Jisheng Zhang <jszhang3@mail.ustc.edu.cn>
To: Andreas Schwab <schwab@linux-m68k.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>
Cc: "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: [PATCH] riscv: Ensure BPF_JIT_REGION_START aligned with PMD size
Date: Tue, 15 Jun 2021 00:49:27 +0800	[thread overview]
Message-ID: <20210615004928.2d27d2ac@xhacker> (raw)
In-Reply-To: <87im2hsfvm.fsf@igel.home>

From: Jisheng Zhang <jszhang@kernel.org>

Andreas reported commit fc8504765ec5 ("riscv: bpf: Avoid breaking W^X")
breaks booting with one kind of config file, I reproduced a kernel panic
with the config:

[    0.138553] Unable to handle kernel paging request at virtual address ffffffff81201220
[    0.139159] Oops [#1]
[    0.139303] Modules linked in:
[    0.139601] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-rc5-default+ #1
[    0.139934] Hardware name: riscv-virtio,qemu (DT)
[    0.140193] epc : __memset+0xc4/0xfc
[    0.140416]  ra : skb_flow_dissector_init+0x1e/0x82
[    0.140609] epc : ffffffff8029806c ra : ffffffff8033be78 sp : ffffffe001647da0
[    0.140878]  gp : ffffffff81134b08 tp : ffffffe001654380 t0 : ffffffff81201158
[    0.141156]  t1 : 0000000000000002 t2 : 0000000000000154 s0 : ffffffe001647dd0
[    0.141424]  s1 : ffffffff80a43250 a0 : ffffffff81201220 a1 : 0000000000000000
[    0.141654]  a2 : 000000000000003c a3 : ffffffff81201258 a4 : 0000000000000064
[    0.141893]  a5 : ffffffff8029806c a6 : 0000000000000040 a7 : ffffffffffffffff
[    0.142126]  s2 : ffffffff81201220 s3 : 0000000000000009 s4 : ffffffff81135088
[    0.142353]  s5 : ffffffff81135038 s6 : ffffffff8080ce80 s7 : ffffffff80800438
[    0.142584]  s8 : ffffffff80bc6578 s9 : 0000000000000008 s10: ffffffff806000ac
[    0.142810]  s11: 0000000000000000 t3 : fffffffffffffffc t4 : 0000000000000000
[    0.143042]  t5 : 0000000000000155 t6 : 00000000000003ff
[    0.143220] status: 0000000000000120 badaddr: ffffffff81201220 cause: 000000000000000f
[    0.143560] [<ffffffff8029806c>] __memset+0xc4/0xfc
[    0.143859] [<ffffffff8061e984>] init_default_flow_dissectors+0x22/0x60
[    0.144092] [<ffffffff800010fc>] do_one_initcall+0x3e/0x168
[    0.144278] [<ffffffff80600df0>] kernel_init_freeable+0x1c8/0x224
[    0.144479] [<ffffffff804868a8>] kernel_init+0x12/0x110
[    0.144658] [<ffffffff800022de>] ret_from_exception+0x0/0xc
[    0.145124] ---[ end trace f1e9643daa46d591 ]---

After some investigation, I think I found the root cause: commit
2bfc6cd81bd ("move kernel mapping outside of linear mapping") moves
BPF JIT region after the kernel:

The &_end is unlikely aligned with PMD size, so the front bpf jit
region sits with part of kernel .data section in one PMD size mapping.
But kernel is mapped in PMD SIZE, 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 to, for example memset the
.data section, MMU will trigger a store page fault.

To fix the issue, we need to ensure the BPF JIT region is PMD size
aligned. This patch acchieve this goal by restoring the BPF JIT region
to original position, I.E the 128MB before kernel .text section.

Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 arch/riscv/include/asm/pgtable.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 9469f464e71a..380cd3a7e548 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -30,9 +30,8 @@
 
 #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_END)
 #else
 #define BPF_JIT_REGION_START	(PAGE_OFFSET - BPF_JIT_REGION_SIZE)
 #define BPF_JIT_REGION_END	(VMALLOC_END)
-- 
2.32.0



_______________________________________________
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linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

  reply	other threads:[~2021-06-14 16:55 UTC|newest]

Thread overview: 63+ 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 18:21 ` 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   ` Jisheng Zhang
2021-03-29 18:22 ` [PATCH 2/9] riscv: Mark some global variables __ro_after_init Jisheng Zhang
2021-03-29 18:22   ` Jisheng Zhang
2021-03-29 18:23 ` [PATCH 3/9] riscv: Constify sys_call_table Jisheng Zhang
2021-03-29 18:23   ` Jisheng Zhang
2021-03-29 18:23 ` [PATCH 4/9] riscv: Constify sbi_ipi_ops Jisheng Zhang
2021-03-29 18:23   ` Jisheng Zhang
2021-03-29 18:24 ` [PATCH 5/9] riscv: kprobes: Implement alloc_insn_page() Jisheng Zhang
2021-03-29 18:24   ` 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 18:24   ` Jisheng Zhang
2021-03-29 20:41   ` Luke Nelson
2021-03-29 20:41     ` Luke Nelson
2021-03-29 18:25 ` [PATCH 7/9] riscv: bpf: Avoid breaking W^X Jisheng Zhang
2021-03-29 18:25   ` Jisheng Zhang
2021-03-30 16:39   ` kernel test robot
2021-06-11 14:10   ` Andreas Schwab
2021-06-11 14:10     ` Andreas Schwab
2021-06-11 16:23     ` Jisheng Zhang
2021-06-11 16:23       ` Jisheng Zhang
2021-06-11 16:41       ` Andreas Schwab
2021-06-11 16:41         ` Andreas Schwab
2021-06-13 17:05         ` Jisheng Zhang
2021-06-13 17:05           ` Jisheng Zhang
2021-06-13 19:50           ` Andreas Schwab
2021-06-13 19:50             ` Andreas Schwab
2021-06-14 16:49             ` Jisheng Zhang [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 12:29                 ` Daniel Borkmann
2021-06-15 18:54               ` Alex Ghiti
2021-06-15 18:54                 ` Alex Ghiti
2021-06-16  0:03                 ` Jisheng Zhang
2021-06-16  0:03                   ` Jisheng Zhang
2021-06-17  7:23                   ` Alex Ghiti
2021-06-17  7:23                     ` Alex Ghiti
2021-06-17 17:17                     ` Jisheng Zhang
2021-06-17 17:17                       ` Jisheng Zhang
2021-06-17  7:30                   ` Palmer Dabbelt
2021-06-17  7:30                     ` Palmer Dabbelt
2021-06-17  8:09                     ` Alex Ghiti
2021-06-17  8:09                       ` Alex Ghiti
2021-06-17 14:18                       ` Alex Ghiti
2021-06-17 14:18                         ` Alex Ghiti
2021-06-17 17:27                         ` Jisheng Zhang
2021-06-17 17:27                           ` Jisheng Zhang
2021-06-17 17:46                           ` Jisheng Zhang
2021-06-17 17:46                             ` Jisheng Zhang
2021-06-17 18:10                             ` Jisheng Zhang
2021-06-17 18:10                               ` Jisheng Zhang
2021-06-17 18:15                               ` [PATCH v2] " Jisheng Zhang
2021-06-17 18:15                                 ` Jisheng Zhang
2021-06-18  6:48                                 ` Alex Ghiti
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 18:25   ` Jisheng Zhang
2021-03-29 18:26 ` [PATCH 9/9] riscv: Set ARCH_HAS_STRICT_MODULE_RWX if MMU Jisheng Zhang
2021-03-29 18:26   ` Jisheng Zhang
2021-04-23  1:48 ` [PATCH 0/9] riscv: improve self-protection Palmer Dabbelt
2021-04-23  1:48   ` Palmer Dabbelt

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