Re: [PATCH v4 2/3] RAS: Fix out-of-bounds read when tracing arm_event

[Hanjun Guo <guohanjun@huawei.com>]

On 2026/9/9 19:28, 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:
> recalculate ctx_len and pei_len based on section_length, limit them,
> and 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.
> 
> Fixes: 05954511b73e ("RAS: Report all ARM processor CPER information to userspace")
> Signed-off-by: Abbott Liu <liuwenliang@huawei.com>
> ---
>   drivers/ras/ras.c | 22 ++++++++++++++++++----
>   1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/ras/ras.c b/drivers/ras/ras.c
> index 2540538a16a8..085fe2d980e5 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;
> @@ -87,14 +87,28 @@ void log_arm_hw_error(struct cper_sec_proc_arm *err, const u8 sev)
>   		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 = 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;
>   	}
> -	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,
> +	trace_arm_event(err, pei_err, (u32)pei_len, ctx_err, (u32)ctx_len,
>   			ven_err_data, (u32)vsei_len, sev, cpu);
>   }

Reviewed-by: Hanjun Guo <guohanjun@huawei.com>

Thanks
Hanjun