2023-12-06 16:55:10

by Alexandre Ghiti

Subject: [PATCH -fixes] riscv: Check if the code to patch lies in the exit section

Otherwise we fall through to vmalloc_to_page() which panics since the
address does not lie in the vmalloc region.

Fixes: 043cb41a85de ("riscv: introduce interfaces to patch kernel code")
Reported-by: [email protected]
Closes: https://lore.kernel.org/all/[email protected]/T/
Signed-off-by: Alexandre Ghiti <[email protected]>
---
arch/riscv/include/asm/sections.h | 1 +
arch/riscv/kernel/patch.c | 11 ++++++++++-
arch/riscv/kernel/vmlinux.lds.S | 2 ++
3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/sections.h b/arch/riscv/include/asm/sections.h
index 32336e8a17cb..a393d5035c54 100644
--- a/arch/riscv/include/asm/sections.h
+++ b/arch/riscv/include/asm/sections.h
@@ -13,6 +13,7 @@ extern char _start_kernel[];
extern char __init_data_begin[], __init_data_end[];
extern char __init_text_begin[], __init_text_end[];
extern char __alt_start[], __alt_end[];
+extern char __exittext_begin[], __exittext_end[];

static inline bool is_va_kernel_text(uintptr_t va)
{
diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
index 13ee7bf589a1..37e87fdcf6a0 100644
--- a/arch/riscv/kernel/patch.c
+++ b/arch/riscv/kernel/patch.c
@@ -14,6 +14,7 @@
#include <asm/fixmap.h>
#include <asm/ftrace.h>
#include <asm/patch.h>
+#include <asm/sections.h>

struct patch_insn {
void *addr;
@@ -25,6 +26,14 @@ struct patch_insn {
int riscv_patch_in_stop_machine = false;

#ifdef CONFIG_MMU
+
+static inline bool is_kernel_exittext(uintptr_t addr)
+{
+ return system_state < SYSTEM_RUNNING &&
+ addr >= (uintptr_t)__exittext_begin &&
+ addr < (uintptr_t)__exittext_end;
+}
+
/*
* The fix_to_virt(, idx) needs a const value (not a dynamic variable of
* reg-a0) or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".
@@ -35,7 +44,7 @@ static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
uintptr_t uintaddr = (uintptr_t) addr;
struct page *page;

- if (core_kernel_text(uintaddr))
+ if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr))
page = phys_to_page(__pa_symbol(addr));
else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
page = vmalloc_to_page(addr);
diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index 492dd4b8f3d6..002ca58dd998 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -69,10 +69,12 @@ SECTIONS
__soc_builtin_dtb_table_end = .;
}
/* we have to discard exit text and such at runtime, not link time */
+ __exittext_begin = .;
.exit.text :
{
EXIT_TEXT
}
+ __exittext_end = .;

__init_text_end = .;
. = ALIGN(SECTION_ALIGN);
--
2.39.2

2023-12-08 16:11:10

by patchwork-bot+linux-riscv

Subject: Re: [PATCH -fixes] riscv: Check if the code to patch lies in the exit section

Hello:

This patch was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <[email protected]>:

On Wed, 6 Dec 2023 17:54:58 +0100 you wrote:
> Otherwise we fall through to vmalloc_to_page() which panics since the
> address does not lie in the vmalloc region.
>
> Fixes: 043cb41a85de ("riscv: introduce interfaces to patch kernel code")
> Reported-by: [email protected]
> Closes: https://lore.kernel.org/all/[email protected]/T/
> Signed-off-by: Alexandre Ghiti <[email protected]>
>
> [...]

Here is the summary with links:
- [-fixes] riscv: Check if the code to patch lies in the exit section
https://git.kernel.org/riscv/c/eb46a0076501

You are awesome, thank you!
--
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