[PATCH] Fix unused memseg length for memory issue

[Yang Ming]

On 2025/1/1 20:34, Dmitry Kozlyuk wrote:
> 2024-12-26 16:10 (UTC+0800), Yang Ming:
>> Fix the issue where OS memory is mistakenly freed with rte_free
>> by setting the length (len) of unused memseg to 0.
>>
>> When eal_legacy_hugepage_init releases the VA space for unused
>> memseg lists, it does not reset their length to 0. As a result,
>> mlx5_mem_is_rte may incorrectly identify OS memory as DPDK
>> memory. This can lead to mlx_free calling rte_free on OS memory,
>> causing an "EAL: Error: Invalid memory" log and failing to free
>> the OS memory.
>>
>> This issue is occasional and occurs when the DPDK program’s
>> memory map places the heap address range between 0 and len(32G).
>> In such cases, malloc may return an address less than len,
>> causing mlx5_mem_is_rte to incorrectly treat it as DPDK memory.
>>
>> Fixes: 66cc45e293ed ("mem: replace memseg with memseg lists")
>> Cc:anatoly.burakov at intel.com
>> Cc:stable at dpdk.org
>>
>> Signed-off-by: Yang Ming<ming.1.yang at nokia-sbell.com>
>> ---
>>   lib/eal/linux/eal_memory.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/lib/eal/linux/eal_memory.c b/lib/eal/linux/eal_memory.c
>> index 45879ca743..9dda60c0e1 100644
>> --- a/lib/eal/linux/eal_memory.c
>> +++ b/lib/eal/linux/eal_memory.c
>> @@ -1472,6 +1472,7 @@ eal_legacy_hugepage_init(void)
>>   		mem_sz = msl->len;
>>   		munmap(msl->base_va, mem_sz);
>>   		msl->base_va = NULL;
>> +		msl->len = 0;
>>   		msl->heap = 0;
>>   
>>   		/* destroy backing fbarray */
> Hi Yang,
>
> It seems the bug affects more than just mlx5 PMD.
>
> Consider how the MSL with `base_va == NULL` ends up in `mlx5_mem_is_rte()`.
> It comes from `rte_mem_virt2memseg_list()` which iterates MSLs
> and checks that an address belongs to [`base_va`; `base_va+len`)
> without checking whether `base_va == NULL` i.e. that the MSL is inactive.
> Your patch also corrects `rte_mem_virt2memseg_list()` behavior.
> Please mention this in the commit message.
>
> Acked-by: Dmitry Kozlyuk<dmitry.kozliuk at gmail.com>

Hi Dmitry,

Thanks. I will update this patch within new version (v2) to add these 
content to the commit log.

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