Messages in this thread Patch in this message | | | Date | Wed, 18 Jan 2023 13:40:17 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm/cma: Fix potential memory loss on cma_declare_contiguous_nid |
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On Wed, 18 Jan 2023 17:05:23 +0900 Levi Yun <ppbuk5246@gmail.com> wrote:
> Suppose, memblock_alloc_ranged_nid with highmem_start is success > when cma_declare_contiguous_nid is called with !fixed > in the system 32-bit system with PHYS_ADDR_T_64BIT enabled > with memblock.bottom_up == false. > > But, Next trial to memblock_alloc_range_nid to allocate in > [SIZE_4G, limits) nullifies former success allocated addr and > it retries to memblock_alloc_ragne_nid again. > > In this situation, first success address area is lost. > > By changing order of allocation (SIZE_4G, high_memory and base) and > checking whether allocated prevents potential memory lost. >
The changelog is hard to follow. I redid it as below - please review and correct if needed?
From: Levi Yun <ppbuk5246@gmail.com> Subject: mm/cma: fix potential memory loss on cma_declare_contiguous_nid Date: Wed, 18 Jan 2023 17:05:23 +0900
Suppose memblock_alloc_range_nid() with highmem_start succeeds when cma_declare_contiguous_nid is called with !fixed on a 32-bit system with PHYS_ADDR_T_64BIT enabled with memblock.bottom_up == false.
But the next trial to memblock_alloc_range_nid() to allocate in [SIZE_4G, limits) nullifies former successfully allocated addr and it retries memblock_alloc_ragne_nid().
In this situation, the first successfully allocated address area is lost.
Change the order of allocation (SIZE_4G, high_memory and base) and check whether the allocated succeeded to prevent potential memory loss.
Link: https://lkml.kernel.org/r/20230118080523.44522-1-ppbuk5246@gmail.com Signed-off-by: Levi Yun <ppbuk5246@gmail.com> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---
mm/cma.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-)
--- a/mm/cma.c~mm-cma-fix-potential-memory-loss-on-cma_declare_contiguous_nid +++ a/mm/cma.c @@ -331,18 +331,6 @@ int __init cma_declare_contiguous_nid(ph phys_addr_t addr = 0; /* - * All pages in the reserved area must come from the same zone. - * If the requested region crosses the low/high memory boundary, - * try allocating from high memory first and fall back to low - * memory in case of failure. - */ - if (base < highmem_start && limit > highmem_start) { - addr = memblock_alloc_range_nid(size, alignment, - highmem_start, limit, nid, true); - limit = highmem_start; - } - - /* * If there is enough memory, try a bottom-up allocation first. * It will place the new cma area close to the start of the node * and guarantee that the compaction is moving pages out of the @@ -359,6 +347,18 @@ int __init cma_declare_contiguous_nid(ph } #endif + /* + * All pages in the reserved area must come from the same zone. + * If the requested region crosses the low/high memory boundary, + * try allocating from high memory first and fall back to low + * memory in case of failure. + */ + if (!addr && base < highmem_start && limit > highmem_start) { + addr = memblock_alloc_range_nid(size, alignment, + highmem_start, limit, nid, true); + limit = highmem_start; + } + if (!addr) { addr = memblock_alloc_range_nid(size, alignment, base, limit, nid, true); _
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