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[2001:1ae9:1c2:4c00:20f:c6b4:1e57:7965]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-aa5997d55fdsm607288366b.55.2024.12.03.04.55.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Dec 2024 04:55:08 -0800 (PST) Date: Tue, 3 Dec 2024 13:55:07 +0100 From: Andrew Jones To: Celeste Liu Cc: Oleg Nesterov , Paul Walmsley , Palmer Dabbelt , Albert Ou , Eric Biederman , Kees Cook , Shuah Khan , Alexandre Ghiti , "Dmitry V. Levin" , Andrea Bolognani , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , Thomas Gleixner , Ron Economos , Charlie Jenkins , Quan Zhou , Felix Yan , Ruizhe Pan , Shiqi Zhang , Guo Ren , Yao Zi , Han Gao , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v2 2/2] riscv: selftests: Add a ptrace test to verify syscall parameter modification Message-ID: <20241203-55c76715e16422ddaf8d7edf@orel> References: <20241203-riscv-new-regset-v2-0-d37da8c0cba6@coelacanthus.name> <20241203-riscv-new-regset-v2-2-d37da8c0cba6@coelacanthus.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241203-riscv-new-regset-v2-2-d37da8c0cba6@coelacanthus.name> X-Rspamd-Queue-Id: C5E6D2000D X-Stat-Signature: pi4abdsguo7me1gcpcxg7a968y5pwdyn X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1733230495-320743 X-HE-Meta: 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 zbeDODHW rGcd8nbDaa+DKIS80JMjPNFLmp6HhetDfKzvTfWJpBwYEFee0OEs6phT3dTmqoJbnNL/Lq9XR7uePbBpcHimHHwuB/1x5fRDkRiu2QWq769PDwp0c2rnjA1zJud7O2Jiwmv5sfc5B58qRcUk2R2UCCLPDyHjdaDbSYhPd0bZ/zVlIEnWimQgoVlmNMc58REc1hiEKmT5Azk+ZlRcM8TSadpC+b1FTugSkqpkyw/e0jbUE39DttZ11QH7yMovcajl+oSB0kGsBuGBbKFEaF1xAslu45zm9CdQuP0av7oX7G2r1tPYUQFlhw340LJy4q22tHBNYtlXIjLw4oxAR8bLvyDyqz/nlI9IXo9Cy73f2xsOhVJ7L2U9Qjn3oQY4NzpgtATL2 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Dec 03, 2024 at 05:30:05PM +0800, Celeste Liu wrote: > From: Charlie Jenkins > > This test checks that orig_a0 allows a syscall argument to be modified, > and that changing a0 does not change the syscall argument. > > Cc: stable@vger.kernel.org > Co-developed-by: Quan Zhou > Signed-off-by: Quan Zhou > Co-developed-by: Celeste Liu > Signed-off-by: Celeste Liu > Signed-off-by: Charlie Jenkins > --- > tools/testing/selftests/riscv/abi/.gitignore | 1 + > tools/testing/selftests/riscv/abi/Makefile | 5 +- > tools/testing/selftests/riscv/abi/ptrace.c | 134 +++++++++++++++++++++++++++ > 3 files changed, 139 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/riscv/abi/.gitignore b/tools/testing/selftests/riscv/abi/.gitignore > index b38358f91c4d2240ae64892871d9ca98bda1ae58..378c605919a3b3d58eec2701eb7af430cfe315d6 100644 > --- a/tools/testing/selftests/riscv/abi/.gitignore > +++ b/tools/testing/selftests/riscv/abi/.gitignore > @@ -1 +1,2 @@ > pointer_masking > +ptrace > diff --git a/tools/testing/selftests/riscv/abi/Makefile b/tools/testing/selftests/riscv/abi/Makefile > index ed82ff9c664e7eb3f760cbab81fb957ff72579c5..3f74d059dfdcbce4d45d8ff618781ccea1419061 100644 > --- a/tools/testing/selftests/riscv/abi/Makefile > +++ b/tools/testing/selftests/riscv/abi/Makefile > @@ -2,9 +2,12 @@ > > CFLAGS += -I$(top_srcdir)/tools/include > > -TEST_GEN_PROGS := pointer_masking > +TEST_GEN_PROGS := pointer_masking ptrace > > include ../../lib.mk > > $(OUTPUT)/pointer_masking: pointer_masking.c > $(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^ > + > +$(OUTPUT)/ptrace: ptrace.c > + $(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^ > diff --git a/tools/testing/selftests/riscv/abi/ptrace.c b/tools/testing/selftests/riscv/abi/ptrace.c > new file mode 100644 > index 0000000000000000000000000000000000000000..d192764b428d1f1c442f3957c6fedeb01a48d556 > --- /dev/null > +++ b/tools/testing/selftests/riscv/abi/ptrace.c > @@ -0,0 +1,134 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#include "../../kselftest_harness.h" > + > +#define ORIG_A0_MODIFY 0x01 > +#define A0_MODIFY 0x02 > +#define A0_OLD 0x03 > +#define A0_NEW 0x04 Shouldn't A0_OLD and A0_NEW set more bits, since 3 and 4 aren't very unique (we could have those values by accident)? And should we include setting bits over 31 for 64-bit targets? > + > +#define perr_and_exit(fmt, ...) \ > + ({ \ > + char buf[256]; \ > + snprintf(buf, sizeof(buf), "%s:%d:" fmt ": %m\n", \ > + __func__, __LINE__, ##__VA_ARGS__); \ > + perror(buf); \ > + exit(-1); \ > + }) Can we use e.g. ksft_exit_fail_perror() instead? I'd prefer we try to consolidate testing/selftests/riscv/* tests on a common format for errors and exit codes and we're already using other kselftest stuff. > + > +static inline void resume_and_wait_tracee(pid_t pid, int flag) > +{ > + int status; > + > + if (ptrace(flag, pid, 0, 0)) > + perr_and_exit("failed to resume the tracee %d\n", pid); > + > + if (waitpid(pid, &status, 0) != pid) > + perr_and_exit("failed to wait for the tracee %d\n", pid); > +} > + > +static void ptrace_test(int opt, int *result) > +{ > + int status; > + pid_t pid; > + struct user_regs_struct regs; > + struct iovec iov = { > + .iov_base = ®s, > + .iov_len = sizeof(regs), > + }; > + > + unsigned long orig_a0; > + struct iovec a0_iov = { > + .iov_base = &orig_a0, > + .iov_len = sizeof(orig_a0), > + }; > + > + pid = fork(); > + if (pid == 0) { > + /* Mark oneself being traced */ > + long val = ptrace(PTRACE_TRACEME, 0, 0, 0); > + > + if (val) > + perr_and_exit("failed to request for tracer to trace me: %ld\n", val); > + > + kill(getpid(), SIGSTOP); > + > + /* Perform exit syscall that will be intercepted */ > + exit(A0_OLD); > + } > + > + if (pid < 0) > + exit(1); This unexpected error condition deserves a message, so I'd use ksft_exit_fail_perror() here. > + > + if (waitpid(pid, &status, 0) != pid) > + perr_and_exit("failed to wait for the tracee %d\n", pid); > + > + /* Stop at the entry point of the syscall */ > + resume_and_wait_tracee(pid, PTRACE_SYSCALL); > + > + /* Check tracee regs before the syscall */ > + if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov)) > + perr_and_exit("failed to get tracee registers\n"); > + if (ptrace(PTRACE_GETREGSET, pid, NT_RISCV_ORIG_A0, &a0_iov)) > + perr_and_exit("failed to get tracee registers\n"); > + if (orig_a0 != A0_OLD) > + perr_and_exit("unexpected orig_a0: 0x%lx\n", orig_a0); > + > + /* Modify a0/orig_a0 for the syscall */ > + switch (opt) { > + case A0_MODIFY: > + regs.a0 = A0_NEW; > + break; > + case ORIG_A0_MODIFY: > + orig_a0 = A0_NEW; > + break; > + } > + > + if (ptrace(PTRACE_SETREGSET, pid, NT_RISCV_ORIG_A0, &a0_iov)) > + perr_and_exit("failed to set tracee registers\n"); > + > + /* Resume the tracee */ > + ptrace(PTRACE_CONT, pid, 0, 0); > + if (waitpid(pid, &status, 0) != pid) > + perr_and_exit("failed to wait for the tracee\n"); > + > + *result = WEXITSTATUS(status); > +} > + > +TEST(ptrace_modify_a0) > +{ > + int result; > + > + ptrace_test(A0_MODIFY, &result); > + > + /* The modification of a0 cannot affect the first argument of the syscall */ > + EXPECT_EQ(A0_OLD, result); What about checking that we actually set regs.a0 to A0_NEW? We'd need A0_NEW to be more unique than 4, though. > +} > + > +TEST(ptrace_modify_orig_a0) > +{ > + int result; > + > + ptrace_test(ORIG_A0_MODIFY, &result); > + > + /* Only modify orig_a0 to change the first argument of the syscall */ If we run ptrace_modify_a0 first then we've already set regs.a0 to A0_NEW and can't check with this test that we don't set it to A0_NEW. We should probably have two different test values, one for regs.a0 and one for orig_a0 and ensure on both tests that we aren't writing both. > + EXPECT_EQ(A0_NEW, result); > +} > + > +TEST_HARNESS_MAIN > > -- > 2.47.0 > Thanks, drew