linux-kernel - Re: [PATCH v2 0/6] mm: Optimize mseal checks

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Message-ID: <CAKbZUD0ZA8q0QdSs_OwbdfSvM3Ze+0MaMQsn2dKM2pN6nn3J4g@mail.gmail.com>
Date: Fri, 16 Aug 2024 19:09:44 +0100
From: Pedro Falcato <pedro.falcato@...il.com>
To: Jeff Xu <jeffxu@...omium.org>
Cc: Jeff Xu <jeffxu@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, oliver.sang@...el.com, 
	torvalds@...ux-foundation.org, Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v2 0/6] mm: Optimize mseal checks

On Fri, Aug 16, 2024 at 6:07 PM Jeff Xu <jeffxu@...omium.org> wrote:
> Please run this test on the latest kernel branch to verify:
>
> static void test_munmap_free_multiple_ranges(bool seal)
> {
>         void *ptr;
>         unsigned long page_size = getpagesize();
>         unsigned long size = 8 * page_size;
>         int ret;
>         int prot;
>
>         setup_single_address(size, &ptr);
>         FAIL_TEST_IF_FALSE(ptr != (void *)-1);
>
>         /* unmap one page from beginning. */
>         ret = sys_munmap(ptr, page_size);
>         FAIL_TEST_IF_FALSE(!ret);
>
>         /* unmap one page from middle. */
>         ret = sys_munmap(ptr + 4 * page_size, page_size);
>         FAIL_TEST_IF_FALSE(!ret);
>
>         /* seal the last page */
>         if (seal) {
>                 ret = sys_mseal(ptr + 7 * page_size, page_size);
>                 FAIL_TEST_IF_FALSE(!ret);
>         }
>
>         /* munmap all 8  pages from beginning */
>         ret = sys_munmap(ptr, 8 * page_size);
>         if (seal) {
>                 FAIL_TEST_IF_FALSE(ret < 0);
>
>                 /* verify none of existing pages in  the range are unmapped */
>                 size = get_vma_size(ptr + page_size, &prot);
>                 FAIL_TEST_IF_FALSE(size == 3 * page_size);
>                 FAIL_TEST_IF_FALSE(prot == 4);
>
>                 size = get_vma_size(ptr +  5 * page_size, &prot);
>                 FAIL_TEST_IF_FALSE(size == 2 * page_size);
>                 FAIL_TEST_IF_FALSE(prot == 4);
>
>                 size = get_vma_size(ptr +  7 * page_size, &prot);
>                 FAIL_TEST_IF_FALSE(size == 1 * page_size);
>                 FAIL_TEST_IF_FALSE(prot == 4);
>         } else {
>                 FAIL_TEST_IF_FALSE(!ret);
>
>                 /* verify all pages are unmapped */
>                 for (int i = 0; i < 8; i++) {
>                         size = get_vma_size(ptr, &prot);
>                         FAIL_TEST_IF_FALSE(size == 0);
>                 }
>         }
>
>         REPORT_TEST_PASS();
> }
>

FWIW this test does not work correctly on my end due to sealed VMAs
getting merged. I hacked up setup_single_address to work around that,
and the test does pass on both 6.10.5 and my local mseal changes
branch.

-- 
Pedro