percpu: fix pcpu_alloc_pages() failure path (f0d27965) · Commits · 戴 / test

When pcpu_alloc_pages() fails midway, pcpu_free_pages() is invoked to free what has already been allocated. The invocation is across the whole requested range and pcpu_free_pages() will try to free all non-NULL pages; unfortunately, this is incorrect as pcpu_get_pages_and_bitmap(), unlike what its comment suggests, doesn't clear the pages array and thus the array may have entries from the previous invocations making the partial failure path free incorrect pages. Fix it by open-coding the partial freeing of the already allocated pages. Signed-off-by:

Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org

mm/percpu-vm.c

+15 −6

Original line number	Diff line number	Diff line
		@@ -108,7 +108,7 @@ static int pcpu_alloc_pages(struct pcpu_chunk *chunk,
		int page_start, int page_end)
		{
		const gfp_t gfp = GFP_KERNEL \| __GFP_HIGHMEM \| __GFP_COLD;
		unsigned int cpu;
		unsigned int cpu, tcpu;
		int i;

		for_each_possible_cpu(cpu) {
		@@ -116,14 +116,23 @@ static int pcpu_alloc_pages(struct pcpu_chunk *chunk,
		struct page **pagep = &pages[pcpu_page_idx(cpu, i)];

		*pagep = alloc_pages_node(cpu_to_node(cpu), gfp, 0);
		if (!*pagep) {
		pcpu_free_pages(chunk, pages, populated,
		page_start, page_end);
		return -ENOMEM;
		}
		if (!*pagep)
		goto err;
		}
		}
		return 0;

		err:
		while (--i >= page_start)
		__free_page(pages[pcpu_page_idx(cpu, i)]);

		for_each_possible_cpu(tcpu) {
		if (tcpu == cpu)
		break;
		for (i = page_start; i < page_end; i++)
		__free_page(pages[pcpu_page_idx(tcpu, i)]);
		}
		return -ENOMEM;
		}

		/**

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