Re: [PATCH] powerpc/kexec_file: Use inclusive range checks in add_usable_mem()

[Sourabh Jain <sourabhjain@linux.ibm.com>]

On 11/08/26 16:25, Thorsten Blum wrote:
> On Tue, Aug 11, 2026 at 11:51:46AM +0530, Sourabh Jain wrote:
>> On 09/08/26 21:54, Thorsten Blum wrote:
>>> add_usable_mem() adds usable memory ranges for the kdump kernel.
>>>
>>> The ranges are inclusive, but the partial overlap check uses exclusive
>>> comparisons. This skips ranges with base == loc_end or end == loc_base.
>>> Use inclusive comparisons instead.
>>>
>>> Fixes: 7c64e21a1c5a ("powerpc/kexec_file: Restrict memory usage of kdump kernel")
>>> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
>>> ---
>>>    arch/powerpc/kexec/file_load_64.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
>>> index 8c72e12ea44e..f9e872693ca7 100644
>>> --- a/arch/powerpc/kexec/file_load_64.c
>>> +++ b/arch/powerpc/kexec/file_load_64.c
>>> @@ -113,7 +113,7 @@ static int add_usable_mem(struct umem_info *um_info, u64 base, u64 end)
>>>    		loc_end = um_info->ranges[i].end;
>>>    		if (loc_base >= base && loc_end <= end)
>>>    			add = true;
>>> -		else if (base < loc_end && end > loc_base) {
>>> +		else if (base <= loc_end && end >= loc_base) {
>> This is interesting. The updated condition basically handles exactly a
>> one-byte overlap on either side of the usable memory ranges. In practice,
>> it is very unlikely that we would have such usable memory and LMB ranges.
>>
>> Thorsten, have you encountered any problem that led you to propose this fix?
> Found by inspection only and I agree that this is unlikely in practice,
> which is why I didn't cc stable. Same for the other patch [1].
>
> Thanks for the review.
>
> [1] https://lore.kernel.org/r/20260810145827.157972-3-thorsten.blum@linux.dev/

The changes look good to me. Feel free to add:

Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>