From: Mike Rapoport <rppt@kernel.org>
To: Hongfu Li <hongfu.li@linux.dev>
Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org,
liam@infradead.org, vbabka@kernel.org, surenb@google.com,
mhocko@suse.com, shuah@kernel.org,
James.Bottomley@hansenpartnership.com, linux-mm@kvack.org,
linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
Hongfu Li <lihongfu@kylinos.cn>
Subject: Re: [PATCH] selftests/mm: fix ptrace PEEKDATA check in memfd_secret test
Date: Tue, 8 Sep 2026 11:08:03 +0300 [thread overview]
Message-ID: <ap_CY1sTymJd8zOy@kernel.org> (raw)
In-Reply-To: <20260908025111.34562-1-hongfu.li@linux.dev>
On Tue, Sep 08, 2026 at 10:51:11AM +0800, Hongfu Li wrote:
> From: Hongfu Li <lihongfu@kylinos.cn>
>
> try_ptrace() treats PTRACE_PEEKDATA return value as a boolean
> check. A successful read returns non-zero data (memory filled with
> 0x55), causing the test to incorrectly report PASS when secret memory
> protection is broken.
>
> Check the return value against -1 instead. The test should only pass
> when PTRACE_PEEKDATA fails, which means secret memory protection works.
>
> Fixes: 76fe17ef588a ("secretmem: test: add basic selftest for memfd_secret(2)")
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
> tools/testing/selftests/mm/memfd_secret.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/mm/memfd_secret.c b/tools/testing/selftests/mm/memfd_secret.c
> index c55d84c5e613..dd08a3a1ef14 100644
> --- a/tools/testing/selftests/mm/memfd_secret.c
> +++ b/tools/testing/selftests/mm/memfd_secret.c
> @@ -145,7 +145,7 @@ static void try_ptrace(int fd, int pipefd[2])
> exit(KSFT_FAIL);
> }
>
> - if (ptrace(PTRACE_PEEKDATA, ppid, mem, 0))
> + if (ptrace(PTRACE_PEEKDATA, ppid, mem, 0) == -1)
> exit(KSFT_PASS);
>
> exit(KSFT_FAIL);
> --
> 2.54.0
>
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2026-09-08 8:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-08 2:51 [PATCH] selftests/mm: fix ptrace PEEKDATA check in memfd_secret test Hongfu Li
2026-09-08 8:08 ` Mike Rapoport [this message]
2026-09-08 9:03 ` Lorenzo Stoakes (ARM)
2026-09-09 6:45 ` Hongfu Li
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