Re: [PATCH] RAS: Fix out-of-range section_length in ARM processor error handling

[Hanjun Guo]

Hi Abbott,

On 2026/8/20 21:18, Abbott Liu wrote:
> Commit 87880af2d24e ("APEI/GHES: ARM processor Error: don't go past
> allocated memory") added bounds checks for malformed ARM processor
> error records but contained several bugs:
>
> - In log_arm_hw_error(), the ctx_info bounds check is inverted. The
>    condition `sz + (long)ctx_info - (long)err >= err->section_length`
>    adds ctx_info->size when the context header is already past the end
>    of the section instead of when it is within bounds. So change the
>    comparison to <=.
>
> - 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.

Please do this in two patches, one for a single issue fix.

> Fixes: 87880af2d24e ("APEI/GHES: ARM processor Error: don't go past allocated memory")
> Signed-off-by: Abbott Liu <liuwenliang@xxxxxxxxxx>
> ---
>   drivers/ras/ras.c | 34 ++++++++++++++++++++++------------
>   1 file changed, 22 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/ras/ras.c b/drivers/ras/ras.c
> index 03df3db62334..e37bf11d0926 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;
> @@ -74,27 +74,37 @@ void log_arm_hw_error(struct cper_sec_proc_arm *err, const u8 sev)
>   	for (n = 0; n < err->context_info_num; n++) {
>   		sz = sizeof(struct cper_arm_ctx_info);
>   
> -		if (sz + (long)ctx_info - (long)err >= err->section_length)
> +		if (sz + (long)ctx_info - (long)err <= err->section_length)
>   			sz += ctx_info->size;
> -

Please leave a empty line here as it is.

Thanks
Hanjun