Re: [PATCH v2] mm/cma: fix reserved page leak on activation failure

[Usama Arif <usama.arif@linux.dev>]

On Sat, 23 May 2026 14:01:23 +0800 Muchun Song <songmuchun@bytedance.com> wrote:

> If cma_activate_area() fails after allocating only part of the range
> bitmaps, the cleanup path still has to release the reserved pages when
> CMA_RESERVE_PAGES_ON_ERROR is clear.
> 
> That is still worth doing even in this __init path. A bitmap_zalloc()
> failure does not necessarily mean the system cannot make further progress:
> freeing the reserved CMA pages can return a substantial amount of memory
> to the buddy allocator and may relieve the temporary memory shortage that
> caused the allocation failure in the first place.
> 
> However, the cleanup path currently uses the bitmap-freeing bound for page
> release as well. That is only correct for ranges whose bitmap allocation
> already succeeded. The failed range and all later ranges still keep their
> reserved pages, so a partial bitmap allocation failure can permanently
> leak them.
> 
> Fix this by releasing reserved pages for all ranges. Use the saved
> early_pfn[] value for ranges whose bitmap allocation already succeeded and
> for the failed range, and use cmr->early_pfn for later ranges whose bitmap
> allocation was never attempted.
> 
> Fixes: c009da4258f9 ("mm, cma: support multiple contiguous ranges, if requested")
> Cc: stable@vger.kernel.org
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>

Acked-by: Usama Arif <usama.arif@linux.dev>