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b=g3hdzvFtn7mdxCrxrK3f5AngKmNRypNNY++sY86OVJO/qKmiyKU9WrgnNlJYMLjzS rUezNUNpyOGzENlX2jUpX6GmHAZDPN5ZdSoA1qij8ljUxe8/2pulEIkfIy4V6g2KPq sqEPAWjYgcQubNLBMwbKfeXvC/EvKPgACWv8kJC1EL011bCB4hhB1pshakHEcfbiQ+ g9qneAn5/Ou+5ppRRsN7fh4XVxkqVrjbqDw8crgiyEVP/y065tOOaVb2vlXQo9H3nW vhdQO1X8MwvcFkcINL09UubOrvH/5hcbmV/tP8BGL8/5DrkpvdFMY/AZ5oiL9mz/lx 4n/aQo3AHB1VA== Date: Tue, 8 Sep 2026 11:08:03 +0300 From: Mike Rapoport To: Hongfu Li 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 Subject: Re: [PATCH] selftests/mm: fix ptrace PEEKDATA check in memfd_secret test Message-ID: References: <20260908025111.34562-1-hongfu.li@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260908025111.34562-1-hongfu.li@linux.dev> X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: isya5mtf8zyz6ssucsqjd88m6exzxcou X-Rspamd-Queue-Id: C3D8C14000F X-HE-Tag: 1788854891-527379 X-HE-Meta: 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 p9WTpEaz W+Zh1l7CnDN+A43VMdo5nom2uoUVGCees2qQbJUqNoSXhZ/omQ4Fbn0Qz6b8xQPTKSKx3A0GsDF1mDCAZpZSFGQmJu+dTLzVzcGHAX3BoKq0uc/umxlzbZWhW9wRBR0U57eVqVHR5AKJ42HOfWEaM3TPE6SWKkBXSXSFFh32Gi2WiwoMfSIbb35dTEe8Ea7Gisd470RPt/vQi6wqgWpXbCO8WwT5u1AIoFh1CriyTlMIjYUVPftJAYIlwcYWJoqtsrj7ufiUZF0PQR7z3fQpmO3RuMS++To1ACOTxEkng/c3pOPa8pITDfTBK3JlSKfimjeguxIEwYxXgEJR6aIoyUHcxBtxd2/CnvLVkBZQhgBe+UvFs1q4MTfU8sQ3R8u6mBMbdUjVAKBPuaT6USHJxOtN0xQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Sep 08, 2026 at 10:51:11AM +0800, Hongfu Li wrote: > From: Hongfu Li > > 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 Acked-by: Mike Rapoport (Microsoft) > --- > 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.