[PATCH master] ARM64: setupc: don't invoke KASAN before relocation

[PATCH master] ARM64: setupc: don't invoke KASAN before relocation

[Ahmad Fatoum]

Plain memset and memcpy are checked by KASAN if enabled before calling
unchecked __memset and __memcpy respectively.

KASAN uses a kasan_initialized variable as first condition in its memory
check, but that only works after relocation. For that reason, we must
take care not to invoke KASAN before then. This was done for ARM32, but
was missing for ARM64. Do so now.

This fixes an annoying issue where network booting a KASAN-enabled barebox
twice in a row would fail: The first happened to work because the memory
kasan_initialized was placed at was zero. The second would behave
erratically, because BSS initialization would silently fail and barebox
static storage would then be initialized with the final values of the
previous run.

Fixes: 932ef7a02e2f ("ARM: Add KASan support")
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
I wondered if there's a way to print a KASAN error that early, but it's
not easy. Calling even global_variable_offset() in kasan_report caused
infinite recursion, despite use of __no_sanitize_address. Printing
unconditionally could be a way around this.
---
 arch/arm/cpu/setupc_64.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/cpu/setupc_64.S b/arch/arm/cpu/setupc_64.S
index d64281c148fc..f38f893be90b 100644
--- a/arch/arm/cpu/setupc_64.S
+++ b/arch/arm/cpu/setupc_64.S
@@ -14,7 +14,7 @@ ENTRY(setup_c)
 	mov	x1, #0
 	ldr	x2, =__bss_stop
 	sub	x2, x2, x0
-	bl	memset			/* clear bss */
+	bl	__memset		/* clear bss */
 	mov	x30, x15
 	ret
 ENDPROC(setup_c)
@@ -63,7 +63,7 @@ ENTRY(relocate_to_adr)
 	sub	x19, x19, x1		/* sub address where we are actually running */
 	add	x19, x19, x0		/* add address where we are going to run */
 
-	bl	memcpy			/* copy binary */
+	bl	__memcpy		/* copy binary */
 
 	bl	sync_caches_for_execution
 
-- 
2.39.2

Re: [PATCH master] ARM64: setupc: don't invoke KASAN before relocation

[Sascha Hauer]

On Sat, Apr 15, 2023 at 10:34:47AM +0200, Ahmad Fatoum wrote:
> Plain memset and memcpy are checked by KASAN if enabled before calling
> unchecked __memset and __memcpy respectively.
> 
> KASAN uses a kasan_initialized variable as first condition in its memory
> check, but that only works after relocation. For that reason, we must
> take care not to invoke KASAN before then. This was done for ARM32, but
> was missing for ARM64. Do so now.
> 
> This fixes an annoying issue where network booting a KASAN-enabled barebox
> twice in a row would fail: The first happened to work because the memory
> kasan_initialized was placed at was zero. The second would behave
> erratically, because BSS initialization would silently fail and barebox
> static storage would then be initialized with the final values of the
> previous run.
> 
> Fixes: 932ef7a02e2f ("ARM: Add KASan support")
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

Applied, thanks

Sascha

> ---
> I wondered if there's a way to print a KASAN error that early, but it's
> not easy. Calling even global_variable_offset() in kasan_report caused
> infinite recursion, despite use of __no_sanitize_address. Printing
> unconditionally could be a way around this.
> ---
>  arch/arm/cpu/setupc_64.S | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/cpu/setupc_64.S b/arch/arm/cpu/setupc_64.S
> index d64281c148fc..f38f893be90b 100644
> --- a/arch/arm/cpu/setupc_64.S
> +++ b/arch/arm/cpu/setupc_64.S
> @@ -14,7 +14,7 @@ ENTRY(setup_c)
>  	mov	x1, #0
>  	ldr	x2, =__bss_stop
>  	sub	x2, x2, x0
> -	bl	memset			/* clear bss */
> +	bl	__memset		/* clear bss */
>  	mov	x30, x15
>  	ret
>  ENDPROC(setup_c)
> @@ -63,7 +63,7 @@ ENTRY(relocate_to_adr)
>  	sub	x19, x19, x1		/* sub address where we are actually running */
>  	add	x19, x19, x0		/* add address where we are going to run */
>  
> -	bl	memcpy			/* copy binary */
> +	bl	__memcpy		/* copy binary */
>  
>  	bl	sync_caches_for_execution
>  
> -- 
> 2.39.2
> 
> 
> 

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