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

[Liuwenliang (Abbott Liu)]

Hi Hanjun, thanks for your review.
>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.

I will change it in next version.

>> 
>> 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.

I will change it in next version.

>Thanks
>Hanjun
>