Re: [PATCH] mm/page_alloc: free allocated PFNs if the range does not match

[Vlastimil Babka (SUSE)]

On 6/30/26 03:35, Zi Yan wrote:
> When using __GFP_COMP in alloc_contig_frozen_range(), if the allocated
> range does not match the requested one, the code errors out with EINVAL
> without freeing the allocated PFNs and causes free page leaks. Fix it by
> calling release_free_list() in the error path.
> 
> The issue is reported by Sashiko[1].

So this?
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>

> Fixes: e98337d11bbd ("mm/contig_alloc: support __GFP_COMP")
> Link: https://sashiko.dev/#/patchset/20260628-keep-subpage-private-zero-at-free-v1-0-f4ce3930d10f@xxxxxxxxxx [1]
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Hm well, it's a path that warns, can only happen due to a development error?
Not sure we care about stable then. Anyway.

Reviewed-by: Vlastimil Babka (SUSE) <vbabka@xxxxxxxxxx>

> ---
> Sashiko reports that if alloc_contig_range() with __GFP_COMP cannot
> allocate PFNs with the given range, it returns EINVAL without freeing the
> allocated PFNs and causes free memory leaks. Fix it by properly freeing the
> isolated free pages and adjusting WARN message for clarification.
> ---
>  mm/compaction.c | 2 +-
>  mm/internal.h   | 1 +
>  mm/page_alloc.c | 6 ++++--
>  3 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index b776f35ad020..4e3f06ff9304 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -88,7 +88,7 @@ static struct page *mark_allocated_noprof(struct page *page, unsigned int order,
>  }
>  #define mark_allocated(...)	alloc_hooks(mark_allocated_noprof(__VA_ARGS__))
>  
> -static unsigned long release_free_list(struct list_head *freepages)
> +unsigned long release_free_list(struct list_head *freepages)
>  {
>  	int order;
>  	unsigned long high_pfn = 0;
> diff --git a/mm/internal.h b/mm/internal.h
> index 181e79f1d6a2..6f9e5c2a6065 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -821,6 +821,7 @@ static inline void clear_zone_contiguous(struct zone *zone)
>  }
>  
>  extern int __isolate_free_page(struct page *page, unsigned int order);
> +extern unsigned long release_free_list(struct list_head *freepages);
>  extern void __putback_isolated_page(struct page *page, unsigned int order,
>  				    int mt);
>  extern void memblock_free_pages(unsigned long pfn, unsigned int order);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ee902a468c2f..c1a35adb40f1 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7235,9 +7235,11 @@ int alloc_contig_frozen_range_noprof(unsigned long start, unsigned long end,
>  		check_new_pages(head, order);
>  		prep_new_page(head, order, gfp_mask, 0);
>  	} else {
> +		release_free_list(cc.freepages);
>  		ret = -EINVAL;
> -		WARN(true, "PFN range: requested [%lu, %lu), allocated [%lu, %lu)\n",
> -		     start, end, outer_start, outer_end);
> +		WARN(true,
> +		     "PFN range: allocated [%lu, %lu) does not match requested [%lu, %lu), freeing allocated PFNs\n",
> +		     outer_start, outer_end, start, end);
>  	}
>  done:
>  	undo_isolate_page_range(start, end);
> 
> ---
> base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
> change-id: 20260629-free-pfn-on-alloc-contig-range-error-path-acc001232468
> 
> Best regards,