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

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Message-ID: <CAKbZUD31EK2ah=vWJ46y4nL9OygzAa6ZxPnPHmWYO-sop5t+5Q@mail.gmail.com>
Date: Fri, 16 Aug 2024 19:26:19 +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 7:20 PM Jeff Xu <jeffxu@...omium.org> wrote:
>
> On Fri, Aug 16, 2024 at 11:09 AM Pedro Falcato <pedro.falcato@...il.com> wrote:
> >
> > 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.
> Yes. you would need to comment out other tests and run this test only,
> it didn't consider the case that sealed vma will merge with another
> sealed vma (created from another test)
>
> The test didn't pass with the V2 patch (the seal = true) case.

Because we... found a bug in my munmap changes. The fixed v3 I'm
planning to send out does indeed pass.

-- 
Pedro