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McKenney" , x86@kernel.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a test that ensures that PKEY-protected struct rseq_cs works and does not lead to process kills. Signed-off-by: Dmitry Vyukov Cc: Mathieu Desnoyers Cc: Peter Zijlstra Cc: "Paul E. McKenney" Cc: Boqun Feng Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" Cc: Aruna Ramakrishna Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org Acked-by: Dave Hansen Fixes: d7822b1e24f2 ("rseq: Introduce restartable sequences system call") --- Changes in v5: - Use static for variables/functions - Use RSEQ_READ/WRITE_ONCE instead of volatile Changes in v4: - Added Fixes tag Changes in v3: - added Acked-by: Dave Hansen - rework the test to work when only pkey 0 is supported for rseq Changes in v2: - change test to install protected rseq_cs instead of rseq --- tools/testing/selftests/rseq/Makefile | 2 +- tools/testing/selftests/rseq/pkey_test.c | 98 ++++++++++++++++++++++++ tools/testing/selftests/rseq/rseq.h | 1 + 3 files changed, 100 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/rseq/Makefile b/tools/testing/selftest= s/rseq/Makefile index 5a3432fceb586..9111d25fea3af 100644 --- a/tools/testing/selftests/rseq/Makefile +++ b/tools/testing/selftests/rseq/Makefile @@ -16,7 +16,7 @@ OVERRIDE_TARGETS =3D 1 =20 TEST_GEN_PROGS =3D basic_test basic_percpu_ops_test basic_percpu_ops_mm_ci= d_test param_test \ param_test_benchmark param_test_compare_twice param_test_mm_cid \ - param_test_mm_cid_benchmark param_test_mm_cid_compare_twice + param_test_mm_cid_benchmark param_test_mm_cid_compare_twice pkey_test =20 TEST_GEN_PROGS_EXTENDED =3D librseq.so =20 diff --git a/tools/testing/selftests/rseq/pkey_test.c b/tools/testing/selft= ests/rseq/pkey_test.c new file mode 100644 index 0000000000000..cc4dd98190942 --- /dev/null +++ b/tools/testing/selftests/rseq/pkey_test.c @@ -0,0 +1,98 @@ +// SPDX-License-Identifier: LGPL-2.1 +/* + * Ensure that rseq works when rseq data is inaccessible due to PKEYs. + */ + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "rseq.h" +#include "rseq-abi.h" + +static int pkey; +static ucontext_t ucp0, ucp1; + +static void coroutine(void) +{ + int i, orig_pk0, old_pk0, old_pk1, pk0, pk1; + /* + * When we disable access to pkey 0, globals and TLS become + * inaccessible too, so we need to tread carefully. + * Pkey is global so we need to copy it onto the stack. + */ + int pk =3D RSEQ_READ_ONCE(pkey); + struct timespec ts; + + orig_pk0 =3D pkey_get(0); + if (pkey_set(0, PKEY_DISABLE_ACCESS)) + err(1, "pkey_set failed"); + old_pk0 =3D pkey_get(0); + old_pk1 =3D pkey_get(pk); + + /* + * Prevent compiler from initializing it by loading a 16-global. + */ + RSEQ_WRITE_ONCE(ts.tv_sec, 0); + RSEQ_WRITE_ONCE(ts.tv_nsec, 10 * 1000); + /* + * If the kernel misbehaves, context switches in the following loop + * will terminate the process with SIGSEGV. + * Trigger preemption w/o accessing TLS. + * Note that glibc's usleep touches errno always. + */ + for (i =3D 0; i < 10; i++) + syscall(SYS_clock_nanosleep, CLOCK_MONOTONIC, 0, &ts, NULL); + + pk0 =3D pkey_get(0); + pk1 =3D pkey_get(pk); + if (pkey_set(0, orig_pk0)) + err(1, "pkey_set failed"); + + /* + * Ensure that the kernel has restored the previous value of pkeys + * register after changing them. + */ + if (old_pk0 !=3D pk0) + errx(1, "pkey 0 changed %d->%d", old_pk0, pk0); + if (old_pk1 !=3D pk1) + errx(1, "pkey 1 changed %d->%d", old_pk1, pk1); + + swapcontext(&ucp1, &ucp0); + abort(); +} + +int main(int argc, char **argv) +{ + pkey =3D pkey_alloc(0, 0); + if (pkey =3D=3D -1) { + printf("[SKIP]\tKernel does not support PKEYs: %s\n", + strerror(errno)); + return 0; + } + + if (rseq_register_current_thread()) + err(1, "rseq_register_current_thread failed"); + + if (getcontext(&ucp1)) + err(1, "getcontext failed"); + ucp1.uc_stack.ss_size =3D getpagesize() * 4; + ucp1.uc_stack.ss_sp =3D mmap(NULL, ucp1.uc_stack.ss_size, + PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0); + if (ucp1.uc_stack.ss_sp =3D=3D MAP_FAILED) + err(1, "mmap failed"); + if (pkey_mprotect(ucp1.uc_stack.ss_sp, ucp1.uc_stack.ss_size, + PROT_READ | PROT_WRITE, pkey)) + err(1, "pkey_mprotect failed"); + makecontext(&ucp1, coroutine, 0); + if (swapcontext(&ucp0, &ucp1)) + err(1, "swapcontext failed"); + return 0; +} diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/= rseq/rseq.h index ba424ce80a719..65da4a727c550 100644 --- a/tools/testing/selftests/rseq/rseq.h +++ b/tools/testing/selftests/rseq/rseq.h @@ -8,6 +8,7 @@ #ifndef RSEQ_H #define RSEQ_H =20 +#include #include #include #include --=20 2.48.1.658.g4767266eb4-goog