| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <87a67bbb-ead4-4dce-85e2-9e67e922571b@arm.com>
Date: Fri, 3 Nov 2023 14:47:13 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Breno Leitao <leitao@...ian.org>
Cc: mike.kravetz@...cle.com, muchun.song@...ux.dev,
akpm@...ux-foundation.org, Shuah Khan <shuah@...nel.org>,
linux-mm@...ck.org, riel@...riel.com,
open list <linux-kernel@...r.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] selftests/mm: Add a new test for madv and hugetlb
On 03/11/2023 13:59, Breno Leitao wrote:
> Hello Ryan,
>
> On Thu, Nov 02, 2023 at 12:29:54PM +0000, Ryan Roberts wrote:
>> On 02/11/2023 12:24, Ryan Roberts wrote:
>>> On 05/10/2023 17:39, Breno Leitao wrote:
>>>> Create a selftest that exercises the race between page faults and
>>>> madvise(MADV_DONTNEED) in the same huge page. Do it by running two
>>>> threads that touches the huge page and madvise(MADV_DONTNEED) at the same
>>>> time.
>>>>
>>>> In case of a SIGBUS coming at pagefault, the test should fail, since we
>>>> hit the bug.
>>>>
>>>> The test doesn't have a signal handler, and if it fails, it fails like
>>>> the following
>>>>
>>>> ----------------------------------
>>>> running ./hugetlb_fault_after_madv
>>>> ----------------------------------
>>>> ./run_vmtests.sh: line 186: 595563 Bus error (core dumped) "$@"
>>>> [FAIL]
>>>>
>>>> This selftest goes together with the fix of the bug[1] itself.
>>>>
>>>> [1] https://lore.kernel.org/all/20231001005659.2185316-1-riel@surriel.com/#r
>>>>
>>>> Signed-off-by: Breno Leitao <leitao@...ian.org>
>>>> ---
>>>> tools/testing/selftests/mm/Makefile | 1 +
>>>> .../selftests/mm/hugetlb_fault_after_madv.c | 73 +++++++++++++++++++
>>>> tools/testing/selftests/mm/run_vmtests.sh | 4 +
>>>> 3 files changed, 78 insertions(+)
>>>> create mode 100644 tools/testing/selftests/mm/hugetlb_fault_after_madv.c
>>>>
>>>> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
>>>> index 6a9fc5693145..e71ec9910c62 100644
>>>> --- a/tools/testing/selftests/mm/Makefile
>>>> +++ b/tools/testing/selftests/mm/Makefile
>>>> @@ -68,6 +68,7 @@ TEST_GEN_FILES += split_huge_page_test
>>>> TEST_GEN_FILES += ksm_tests
>>>> TEST_GEN_FILES += ksm_functional_tests
>>>> TEST_GEN_FILES += mdwe_test
>>>> +TEST_GEN_FILES += hugetlb_fault_after_madv
>>>>
>>>> ifneq ($(ARCH),arm64)
>>>> TEST_GEN_PROGS += soft-dirty
>>>> diff --git a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c
>>>> new file mode 100644
>>>> index 000000000000..73b81c632366
>>>> --- /dev/null
>>>> +++ b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c
>>>> @@ -0,0 +1,73 @@
>>>> +// SPDX-License-Identifier: GPL-2.0
>>>> +#include <pthread.h>
>>>> +#include <stdio.h>
>>>> +#include <stdlib.h>
>>>> +#include <sys/mman.h>
>>>> +#include <sys/types.h>
>>>> +#include <unistd.h>
>>>> +
>>>> +#include "vm_util.h"
>>>> +#include "../kselftest.h"
>>>> +
>>>> +#define MMAP_SIZE (1 << 21)
>>>> +#define INLOOP_ITER 100
>>>> +
>>>> +char *huge_ptr;
>>>> +
>>>> +/* Touch the memory while it is being madvised() */
>>>> +void *touch(void *unused)
>>>> +{
>>>> + char *ptr = (char *)huge_ptr;
>>>> +
>>>> + for (int i = 0; i < INLOOP_ITER; i++)
>>>> + ptr[0] = '.';
>>>> +
>>>> + return NULL;
>>>> +}
>>>> +
>>>> +void *madv(void *unused)
>>>> +{
>>>> + usleep(rand() % 10);
>>>> +
>>>> + for (int i = 0; i < INLOOP_ITER; i++)
>>>> + madvise(huge_ptr, MMAP_SIZE, MADV_DONTNEED);
>>>> +
>>>> + return NULL;
>>>> +}
>>>> +
>>>> +int main(void)
>>>> +{
>>>> + unsigned long free_hugepages;
>>>> + pthread_t thread1, thread2;
>>>> + /*
>>>> + * On kernel 6.4, we are able to reproduce the problem with ~1000
>>>> + * interactions
>>>> + */
>>>> + int max = 10000;
>>>> +
>>>> + srand(getpid());
>>>> +
>>>> + free_hugepages = get_free_hugepages();
>>>> + if (free_hugepages != 1) {
>>>> + ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n",
>>>> + free_hugepages);
>>>> + }
>>>> +
>>>> + while (max--) {
>>>> + huge_ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE,
>>>> + MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB,
>>>> + -1, 0);
>>>> +
>>>> + if ((unsigned long)huge_ptr == -1)
>>>> + ksft_exit_skip("Failed to allocated huge page\n");
>>>> +
>>>> + pthread_create(&thread1, NULL, madv, NULL);
>>>> + pthread_create(&thread2, NULL, touch, NULL);
>>>> +
>>>> + pthread_join(thread1, NULL);
>>>> + pthread_join(thread2, NULL);
>>>> + munmap(huge_ptr, MMAP_SIZE);
>>>> + }
>>>> +
>>>> + return KSFT_PASS;
>>>> +}
>>>> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
>>>> index 3e2bc818d566..9f53f7318a38 100755
>>>> --- a/tools/testing/selftests/mm/run_vmtests.sh
>>>> +++ b/tools/testing/selftests/mm/run_vmtests.sh
>>>> @@ -221,6 +221,10 @@ CATEGORY="hugetlb" run_test ./hugepage-mremap
>>>> CATEGORY="hugetlb" run_test ./hugepage-vmemmap
>>>> CATEGORY="hugetlb" run_test ./hugetlb-madvise
>>>>
>>>> +# For this test, we need one and just one huge page
>>>> +echo 1 > /proc/sys/vm/nr_hugepages
>>>
>>> I've noticed that this change breaks some of the uffd-stress tests further down
>>> the file, because you have freed previously reserved hugepages that the test
>>> requires to run. I notice that the patch is already in mm-stable, so perhaps its
>>> possible to submit a patch that does a save and restore?
>>>
>>> Although I'm not sure if that might be tricky because the previous reservation
>>> is per-size and per-node (our CI does this on the kernel command line), and I
>>> suspect if you want just 1 huge page in the entire system you won't be able to
>>> get back to the previous state by just restoring this value?
>>
>> Actually on closer inspection, I don't think this will be a problem; simply
>> saving and restoring the value around the test will be sufficient.
>
> Thanks for checking it, I will prepare a patch that will restore the number
> of huge pages allocated after the test.
>
>> I also notice that the binary for the new test is not added to the .gitignore,
>> which is a minor annoyance.
>
> I will add the file to .gitignore also.
Excellent - thanks!
>
> Thanks for the heads-up.
Powered by blists - more mailing lists