Re: [PATCH v2 2/2] RAS: Fix out-of-bounds read when tracing arm_event

[Hanjun Guo <guohanjun@huawei.com>]

On 2026/8/25 21:43, Abbott Liu wrote:
> The vsei_len < 0 error path did not verify the pei_len and ctx_len.
> When vsei_len is negative, section_length is too small to hold the
> full record, yet pei_len and ctx_len were derived from
> err_info_num/context_info_num and may describe regions beyond the
> (long)err .. err + section_length buffer. To prevent trace_arm_event
> from reading past the allocated record, sanitize the parameters:
> move the cpu lookup above this path so it is available for tracing,
> recalculate ctx_len and pei_len based on section_length, limit them,
> set the corresponding pointers to NULL and lengths to 0  when there
> is no remaining space.
> 
> pei_len and ctx_len become s32 so that the recalculated lengths can
> be checked for negative values, and the cpu lookup is moved above the
> section length checks so that both paths can share the final
> trace_arm_event() call.
> 
> Fixes: 05954511b73e ("RAS: Report all ARM processor CPER information to userspace")
> 

Same here, no empty line between Fixes and Signed-off-by.

> Signed-off-by: Abbott Liu <liuwenliang@huawei.com>
> ---
>   drivers/ras/ras.c | 31 +++++++++++++++++++++----------
>   1 file changed, 21 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/ras/ras.c b/drivers/ras/ras.c
> index 2540538a16a8..4a48a897f616 100644
> --- a/drivers/ras/ras.c
> +++ b/drivers/ras/ras.c
> @@ -58,10 +58,10 @@ void log_arm_hw_error(struct cper_sec_proc_arm *err, const u8 sev)
>   	struct cper_arm_err_info *err_info;
>   	struct cper_arm_ctx_info *ctx_info;
>   	u8 *ven_err_data;
> -	u32 ctx_len = 0;
> +	s32 ctx_len = 0;
>   	int n, sz, cpu;
>   	s32 vsei_len;
> -	u32 pei_len;
> +	s32 pei_len;
>   	u8 *pei_err, *ctx_err;
>   
>   	pei_len = sizeof(struct cper_arm_err_info) * err->err_info_num;
> @@ -81,20 +81,31 @@ void log_arm_hw_error(struct cper_sec_proc_arm *err, const u8 sev)
>   		ctx_len += sz;
>   	}
>   
> +	cpu = GET_LOGICAL_INDEX(err->mpidr);
> +	if (cpu < 0)
> +		cpu = -1;
> +
>   	vsei_len = err->section_length - (sizeof(struct cper_sec_proc_arm) + pei_len + ctx_len);
>   	if (vsei_len < 0) {
>   		pr_warn(FW_BUG "section length: %d\n", err->section_length);
>   		pr_warn(FW_BUG "section length is too small\n");
>   		pr_warn(FW_BUG "firmware-generated error record is incorrect\n");
>   		vsei_len = 0;
> -	}
> -	ven_err_data = (u8 *)ctx_info;
> -
> -	cpu = GET_LOGICAL_INDEX(err->mpidr);
> -	if (cpu < 0)
> -		cpu = -1;
> -
> -	trace_arm_event(err, pei_err, pei_len, ctx_err, ctx_len,
> +		ven_err_data = NULL;
> +		ctx_len = err->section_length - (sizeof(struct cper_sec_proc_arm) + pei_len);
> +		if (ctx_len < 0) {
> +			ctx_len = 0;
> +			ctx_err = NULL;
> +			pei_len = err->section_length - sizeof(struct cper_sec_proc_arm);
> +			if (pei_len < 0) {
> +				pei_len = 0;
> +				pei_err = NULL;
> +			}
> +		}
> +	} else
> +		ven_err_data = (u8 *)ctx_info;

else {
	ven_err_data = (u8 *)ctx_info;
}

Thanks
Hanjun