| Message ID | 20220927110120.106906-2-david@redhat.com |
|---|---|
| State | Accepted |
| Commit | 69c66add566395eaf4c08cb5975b45dec70dbe85 |
| Headers | show |
| Series | selftests/vm: test COW handling of anonymous memory | expand |
On Tue, Sep 27, 2022 at 01:01:14PM +0200, David Hildenbrand wrote: > Let's start adding tests for our COW handling of anonymous memory. We'll > focus on basic tests that we can achieve without additional libraries or > gup_test extensions. > > We'll add THP and hugetlb tests separately. > > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > tools/testing/selftests/vm/.gitignore | 1 + > tools/testing/selftests/vm/Makefile | 4 +- > tools/testing/selftests/vm/anon_cow.c | 401 ++++++++++++++++++++++ > tools/testing/selftests/vm/run_vmtests.sh | 3 + > tools/testing/selftests/vm/vm_util.c | 7 + > tools/testing/selftests/vm/vm_util.h | 1 + > 6 files changed, 416 insertions(+), 1 deletion(-) > create mode 100644 tools/testing/selftests/vm/anon_cow.c > > diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore > index 7b9dc2426f18..8a536c731e3c 100644 > --- a/tools/testing/selftests/vm/.gitignore > +++ b/tools/testing/selftests/vm/.gitignore > @@ -1,4 +1,5 @@ > # SPDX-License-Identifier: GPL-2.0-only > +anon_cow > hugepage-mmap > hugepage-mremap > hugepage-shm > diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile > index 4ae879f70f4c..bc759534ec28 100644 > --- a/tools/testing/selftests/vm/Makefile > +++ b/tools/testing/selftests/vm/Makefile > @@ -25,7 +25,8 @@ MAKEFLAGS += --no-builtin-rules > > CFLAGS = -Wall -I ../../../../usr/include $(EXTRA_CFLAGS) $(KHDR_INCLUDES) > LDLIBS = -lrt -lpthread > -TEST_GEN_FILES = compaction_test > +TEST_GEN_FILES = anon_cow > +TEST_GEN_FILES += compaction_test > TEST_GEN_FILES += gup_test > TEST_GEN_FILES += hmm-tests > TEST_GEN_FILES += hugetlb-madvise > @@ -95,6 +96,7 @@ TEST_FILES += va_128TBswitch.sh > > include ../lib.mk > > +$(OUTPUT)/anon_cow: vm_util.c > $(OUTPUT)/madv_populate: vm_util.c > $(OUTPUT)/soft-dirty: vm_util.c > $(OUTPUT)/split_huge_page_test: vm_util.c > diff --git a/tools/testing/selftests/vm/anon_cow.c b/tools/testing/selftests/vm/anon_cow.c > new file mode 100644 > index 000000000000..9d2b15c829e6 > --- /dev/null > +++ b/tools/testing/selftests/vm/anon_cow.c > @@ -0,0 +1,401 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * COW (Copy On Write) tests for anonymous memory. > + * > + * Copyright 2022, Red Hat, Inc. > + * > + * Author(s): David Hildenbrand <david@redhat.com> > + */ > +#define _GNU_SOURCE > +#include <stdlib.h> > +#include <string.h> > +#include <stdbool.h> > +#include <stdint.h> > +#include <unistd.h> > +#include <errno.h> > +#include <fcntl.h> > +#include <dirent.h> > +#include <assert.h> > +#include <sys/mman.h> > +#include <sys/wait.h> > + > +#include "../kselftest.h" > +#include "vm_util.h" > + > +static size_t pagesize; > +static int pagemap_fd; > + > +struct comm_pipes { > + int child_ready[2]; > + int parent_ready[2]; > +}; > + > +static int setup_comm_pipes(struct comm_pipes *comm_pipes) > +{ > + if (pipe(comm_pipes->child_ready) < 0) > + return -errno; > + if (pipe(comm_pipes->parent_ready) < 0) { > + close(comm_pipes->child_ready[0]); > + close(comm_pipes->child_ready[1]); > + return -errno; > + } > + > + return 0; > +} > + > +static void close_comm_pipes(struct comm_pipes *comm_pipes) > +{ > + close(comm_pipes->child_ready[0]); > + close(comm_pipes->child_ready[1]); > + close(comm_pipes->parent_ready[0]); > + close(comm_pipes->parent_ready[1]); > +} > + > +static int child_memcmp_fn(char *mem, size_t size, > + struct comm_pipes *comm_pipes) > +{ > + char *old = malloc(size); > + char buf; > + > + /* Backup the original content. */ > + memcpy(old, mem, size); > + > + /* Wait until the parent modified the page. */ > + write(comm_pipes->child_ready[1], "0", 1); > + while (read(comm_pipes->parent_ready[0], &buf, 1) != 1) > + ; > + > + /* See if we still read the old values. */ > + return memcmp(old, mem, size); > +} > + > +static int child_vmsplice_memcmp_fn(char *mem, size_t size, > + struct comm_pipes *comm_pipes) > +{ > + struct iovec iov = { > + .iov_base = mem, > + .iov_len = size, > + }; > + size_t cur, total, transferred; > + char *old, *new; > + int fds[2]; > + char buf; > + > + old = malloc(size); > + new = malloc(size); > + > + /* Backup the original content. */ > + memcpy(old, mem, size); > + > + if (pipe(fds) < 0) > + return -errno; > + > + /* Trigger a read-only pin. */ > + transferred = vmsplice(fds[1], &iov, 1, 0); > + if (transferred < 0) > + return -errno; > + if (transferred == 0) > + return -EINVAL; > + > + /* Unmap it from our page tables. */ > + if (munmap(mem, size) < 0) > + return -errno; > + > + /* Wait until the parent modified it. */ > + write(comm_pipes->child_ready[1], "0", 1); > + while (read(comm_pipes->parent_ready[0], &buf, 1) != 1) > + ; > + > + /* See if we still read the old values via the pipe. */ > + for (total = 0; total < transferred; total += cur) { > + cur = read(fds[0], new + total, transferred - total); > + if (cur < 0) Hi David, I was looking at some coccinelle reports for linux-next and saw the following warning for this comparison: WARNING: Unsigned expression compared with zero: cur < 0 I think 'cur' needs to be of type 'ssize_t' for this comparison to work. The same warning is reported for the variable 'transferred' above, and also for do_test_iouring() and do_test_vmsplice_in_parent() in "selftests/vm: anon_cow: add liburing test cases". > + return -errno; > + } > + > + return memcmp(old, new, transferred); > +} > + > +typedef int (*child_fn)(char *mem, size_t size, struct comm_pipes *comm_pipes); > + > +static void do_test_cow_in_parent(char *mem, size_t size, child_fn fn) > +{ > + struct comm_pipes comm_pipes; > + char buf; > + int ret; > + > + ret = setup_comm_pipes(&comm_pipes); > + if (ret) { > + ksft_test_result_fail("pipe() failed\n"); > + return; > + } > + > + ret = fork(); > + if (ret < 0) { > + ksft_test_result_fail("fork() failed\n"); > + goto close_comm_pipes; > + } else if (!ret) { > + exit(fn(mem, size, &comm_pipes)); > + } > + > + while (read(comm_pipes.child_ready[0], &buf, 1) != 1) > + ; > + /* Modify the page. */ > + memset(mem, 0xff, size); > + write(comm_pipes.parent_ready[1], "0", 1); > + > + wait(&ret); > + if (WIFEXITED(ret)) > + ret = WEXITSTATUS(ret); > + else > + ret = -EINVAL; > + > + ksft_test_result(!ret, "No leak from parent into child\n"); > +close_comm_pipes: > + close_comm_pipes(&comm_pipes); > +} > + > +static void test_cow_in_parent(char *mem, size_t size) > +{ > + do_test_cow_in_parent(mem, size, child_memcmp_fn); > +} > + > +static void test_vmsplice_in_child(char *mem, size_t size) > +{ > + do_test_cow_in_parent(mem, size, child_vmsplice_memcmp_fn); > +} > + > +static void do_test_vmsplice_in_parent(char *mem, size_t size, > + bool before_fork) > +{ > + struct iovec iov = { > + .iov_base = mem, > + .iov_len = size, > + }; > + size_t cur, total, transferred; > + struct comm_pipes comm_pipes; > + char *old, *new; > + int ret, fds[2]; > + char buf; > + > + old = malloc(size); > + new = malloc(size); > + > + memcpy(old, mem, size); > + > + ret = setup_comm_pipes(&comm_pipes); > + if (ret) { > + ksft_test_result_fail("pipe() failed\n"); > + goto free; > + } > + > + if (pipe(fds) < 0) { > + ksft_test_result_fail("pipe() failed\n"); > + goto close_comm_pipes; > + } > + > + if (before_fork) { > + transferred = vmsplice(fds[1], &iov, 1, 0); > + if (transferred <= 0) { > + ksft_test_result_fail("vmsplice() failed\n"); > + goto close_pipe; > + } > + } > + > + ret = fork(); > + if (ret < 0) { > + ksft_test_result_fail("fork() failed\n"); > + goto close_pipe; > + } else if (!ret) { > + write(comm_pipes.child_ready[1], "0", 1); > + while (read(comm_pipes.parent_ready[0], &buf, 1) != 1) > + ; > + /* Modify page content in the child. */ > + memset(mem, 0xff, size); > + exit(0); > + } > + > + if (!before_fork) { > + transferred = vmsplice(fds[1], &iov, 1, 0); > + if (transferred <= 0) { > + ksft_test_result_fail("vmsplice() failed\n"); > + wait(&ret); > + goto close_pipe; > + } > + } > + > + while (read(comm_pipes.child_ready[0], &buf, 1) != 1) > + ; > + if (munmap(mem, size) < 0) { > + ksft_test_result_fail("munmap() failed\n"); > + goto close_pipe; > + } > + write(comm_pipes.parent_ready[1], "0", 1); > + > + /* Wait until the child is done writing. */ > + wait(&ret); > + if (!WIFEXITED(ret)) { > + ksft_test_result_fail("wait() failed\n"); > + goto close_pipe; > + } > + > + /* See if we still read the old values. */ > + for (total = 0; total < transferred; total += cur) { > + cur = read(fds[0], new + total, transferred - total); > + if (cur < 0) { > + ksft_test_result_fail("read() failed\n"); > + goto close_pipe; > + } > + } > + > + ksft_test_result(!memcmp(old, new, transferred), > + "No leak from child into parent\n"); > +close_pipe: > + close(fds[0]); > + close(fds[1]); > +close_comm_pipes: > + close_comm_pipes(&comm_pipes); > +free: > + free(old); > + free(new); > +} > + > +static void test_vmsplice_before_fork(char *mem, size_t size) > +{ > + do_test_vmsplice_in_parent(mem, size, true); > +} > + > +static void test_vmsplice_after_fork(char *mem, size_t size) > +{ > + do_test_vmsplice_in_parent(mem, size, false); > +} > + > +typedef void (*test_fn)(char *mem, size_t size); > + > +static void do_run_with_base_page(test_fn fn, bool swapout) > +{ > + char *mem; > + int ret; > + > + mem = mmap(NULL, pagesize, PROT_READ | PROT_WRITE, > + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > + if (mem == MAP_FAILED) { > + ksft_test_result_fail("mmap() failed\n"); > + return; > + } > + > + ret = madvise(mem, pagesize, MADV_NOHUGEPAGE); > + /* Ignore if not around on a kernel. */ > + if (ret && errno != EINVAL) { > + ksft_test_result_fail("MADV_NOHUGEPAGE failed\n"); > + goto munmap; > + } > + > + /* Populate a base page. */ > + memset(mem, 0, pagesize); > + > + if (swapout) { > + madvise(mem, pagesize, MADV_PAGEOUT); > + if (!pagemap_is_swapped(pagemap_fd, mem)) { > + ksft_test_result_skip("MADV_PAGEOUT did not work, is swap enabled?\n"); > + goto munmap; > + } > + } > + > + fn(mem, pagesize); > +munmap: > + munmap(mem, pagesize); > +} > + > +static void run_with_base_page(test_fn fn, const char *desc) > +{ > + ksft_print_msg("[RUN] %s ... with base page\n", desc); > + do_run_with_base_page(fn, false); > +} > + > +static void run_with_base_page_swap(test_fn fn, const char *desc) > +{ > + ksft_print_msg("[RUN] %s ... with swapped out base page\n", desc); > + do_run_with_base_page(fn, true); > +} > + > +struct test_case { > + const char *desc; > + test_fn fn; > +}; > + > +static const struct test_case test_cases[] = { > + /* > + * Basic COW tests for fork() without any GUP. If we miss to break COW, > + * either the child can observe modifications by the parent or the > + * other way around. > + */ > + { > + "Basic COW after fork()", > + test_cow_in_parent, > + }, > + /* > + * vmsplice() [R/O GUP] + unmap in the child; modify in the parent. If > + * we miss to break COW, the child observes modifications by the parent. > + * This is CVE-2020-29374 reported by Jann Horn. > + */ > + { > + "vmsplice() + unmap in child", > + test_vmsplice_in_child > + }, > + /* > + * vmsplice() [R/O GUP] in parent before fork(), unmap in parent after > + * fork(); modify in the child. If we miss to break COW, the parent > + * observes modifications by the child. > + */ > + { > + "vmsplice() before fork(), unmap in parent after fork()", > + test_vmsplice_before_fork, > + }, > + /* > + * vmsplice() [R/O GUP] + unmap in parent after fork(); modify in the > + * child. If we miss to break COW, the parent observes modifications by > + * the child. > + */ > + { > + "vmsplice() + unmap in parent after fork()", > + test_vmsplice_after_fork, > + }, > +}; > + > +static void run_test_case(struct test_case const *test_case) > +{ > + run_with_base_page(test_case->fn, test_case->desc); > + run_with_base_page_swap(test_case->fn, test_case->desc); > +} > + > +static void run_test_cases(void) > +{ > + int i; > + > + for (i = 0; i < ARRAY_SIZE(test_cases); i++) > + run_test_case(&test_cases[i]); > +} > + > +int main(int argc, char **argv) > +{ > + int nr_test_cases = ARRAY_SIZE(test_cases); > + int err; > + > + pagesize = getpagesize(); > + > + ksft_print_header(); > + ksft_set_plan(nr_test_cases * 2); > + > + pagemap_fd = open("/proc/self/pagemap", O_RDONLY); > + if (pagemap_fd < 0) > + ksft_exit_fail_msg("opening pagemap failed\n"); > + > + run_test_cases(); > + > + err = ksft_get_fail_cnt(); > + if (err) > + ksft_exit_fail_msg("%d out of %d tests failed\n", > + err, ksft_test_num()); > + return ksft_exit_pass(); > +} > diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh > index e780e76c26b8..af59380bc254 100755 > --- a/tools/testing/selftests/vm/run_vmtests.sh > +++ b/tools/testing/selftests/vm/run_vmtests.sh > @@ -197,4 +197,7 @@ fi > > run_test ./soft-dirty > > +# COW tests for anonymous memory > +run_test ./anon_cow > + > exit $exitcode > diff --git a/tools/testing/selftests/vm/vm_util.c b/tools/testing/selftests/vm/vm_util.c > index b58ab11a7a30..6456027e1985 100644 > --- a/tools/testing/selftests/vm/vm_util.c > +++ b/tools/testing/selftests/vm/vm_util.c > @@ -28,6 +28,13 @@ bool pagemap_is_softdirty(int fd, char *start) > return entry & 0x0080000000000000ull; > } > > +bool pagemap_is_swapped(int fd, char *start) > +{ > + uint64_t entry = pagemap_get_entry(fd, start); > + > + return entry & 0x4000000000000000ull; > +} > + > void clear_softdirty(void) > { > int ret; > diff --git a/tools/testing/selftests/vm/vm_util.h b/tools/testing/selftests/vm/vm_util.h > index 2e512bd57ae1..bb8ec8d69623 100644 > --- a/tools/testing/selftests/vm/vm_util.h > +++ b/tools/testing/selftests/vm/vm_util.h > @@ -4,6 +4,7 @@ > > uint64_t pagemap_get_entry(int fd, char *start); > bool pagemap_is_softdirty(int fd, char *start); > +bool pagemap_is_swapped(int fd, char *start); > void clear_softdirty(void); > uint64_t read_pmd_pagesize(void); > uint64_t check_huge(void *addr); > -- > 2.37.3 >
>> + /* See if we still read the old values via the pipe. */ >> + for (total = 0; total < transferred; total += cur) { >> + cur = read(fds[0], new + total, transferred - total); >> + if (cur < 0) > > Hi David, > I was looking at some coccinelle reports for linux-next and > saw the following warning for this comparison: > > WARNING: Unsigned expression compared with zero: cur < 0 > > I think 'cur' needs to be of type 'ssize_t' for this comparison to work. > > The same warning is reported for the variable 'transferred' above, and > also for do_test_iouring() and do_test_vmsplice_in_parent() in > "selftests/vm: anon_cow: add liburing test cases". > Thanks for reporting! Indeed, we need a signed value.
On 27.09.22 13:01, David Hildenbrand wrote: > Let's start adding tests for our COW handling of anonymous memory. We'll > focus on basic tests that we can achieve without additional libraries or > gup_test extensions. > > We'll add THP and hugetlb tests separately. > > Signed-off-by: David Hildenbrand <david@redhat.com> > --- The following fixup on top: diff --git a/tools/testing/selftests/vm/anon_cow.c b/tools/testing/selftests/vm/anon_cow.c index 9d2b15c829e6..4613294af758 100644 --- a/tools/testing/selftests/vm/anon_cow.c +++ b/tools/testing/selftests/vm/anon_cow.c @@ -76,7 +76,7 @@ static int child_vmsplice_memcmp_fn(char *mem, size_t size, .iov_base = mem, .iov_len = size, }; - size_t cur, total, transferred; + ssize_t cur, total, transferred; char *old, *new; int fds[2]; char buf; @@ -172,7 +172,7 @@ static void do_test_vmsplice_in_parent(char *mem, size_t size, .iov_base = mem, .iov_len = size, }; - size_t cur, total, transferred; + ssize_t cur, total, transferred; struct comm_pipes comm_pipes; char *old, *new; int ret, fds[2];
diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore index 7b9dc2426f18..8a536c731e3c 100644 --- a/tools/testing/selftests/vm/.gitignore +++ b/tools/testing/selftests/vm/.gitignore @@ -1,4 +1,5 @@ # SPDX-License-Identifier: GPL-2.0-only +anon_cow hugepage-mmap hugepage-mremap hugepage-shm diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile index 4ae879f70f4c..bc759534ec28 100644 --- a/tools/testing/selftests/vm/Makefile +++ b/tools/testing/selftests/vm/Makefile @@ -25,7 +25,8 @@ MAKEFLAGS += --no-builtin-rules CFLAGS = -Wall -I ../../../../usr/include $(EXTRA_CFLAGS) $(KHDR_INCLUDES) LDLIBS = -lrt -lpthread -TEST_GEN_FILES = compaction_test +TEST_GEN_FILES = anon_cow +TEST_GEN_FILES += compaction_test TEST_GEN_FILES += gup_test TEST_GEN_FILES += hmm-tests TEST_GEN_FILES += hugetlb-madvise @@ -95,6 +96,7 @@ TEST_FILES += va_128TBswitch.sh include ../lib.mk +$(OUTPUT)/anon_cow: vm_util.c $(OUTPUT)/madv_populate: vm_util.c $(OUTPUT)/soft-dirty: vm_util.c $(OUTPUT)/split_huge_page_test: vm_util.c diff --git a/tools/testing/selftests/vm/anon_cow.c b/tools/testing/selftests/vm/anon_cow.c new file mode 100644 index 000000000000..9d2b15c829e6 --- /dev/null +++ b/tools/testing/selftests/vm/anon_cow.c @@ -0,0 +1,401 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * COW (Copy On Write) tests for anonymous memory. + * + * Copyright 2022, Red Hat, Inc. + * + * Author(s): David Hildenbrand <david@redhat.com> + */ +#define _GNU_SOURCE +#include <stdlib.h> +#include <string.h> +#include <stdbool.h> +#include <stdint.h> +#include <unistd.h> +#include <errno.h> +#include <fcntl.h> +#include <dirent.h> +#include <assert.h> +#include <sys/mman.h> +#include <sys/wait.h> + +#include "../kselftest.h" +#include "vm_util.h" + +static size_t pagesize; +static int pagemap_fd; + +struct comm_pipes { + int child_ready[2]; + int parent_ready[2]; +}; + +static int setup_comm_pipes(struct comm_pipes *comm_pipes) +{ + if (pipe(comm_pipes->child_ready) < 0) + return -errno; + if (pipe(comm_pipes->parent_ready) < 0) { + close(comm_pipes->child_ready[0]); + close(comm_pipes->child_ready[1]); + return -errno; + } + + return 0; +} + +static void close_comm_pipes(struct comm_pipes *comm_pipes) +{ + close(comm_pipes->child_ready[0]); + close(comm_pipes->child_ready[1]); + close(comm_pipes->parent_ready[0]); + close(comm_pipes->parent_ready[1]); +} + +static int child_memcmp_fn(char *mem, size_t size, + struct comm_pipes *comm_pipes) +{ + char *old = malloc(size); + char buf; + + /* Backup the original content. */ + memcpy(old, mem, size); + + /* Wait until the parent modified the page. */ + write(comm_pipes->child_ready[1], "0", 1); + while (read(comm_pipes->parent_ready[0], &buf, 1) != 1) + ; + + /* See if we still read the old values. */ + return memcmp(old, mem, size); +} + +static int child_vmsplice_memcmp_fn(char *mem, size_t size, + struct comm_pipes *comm_pipes) +{ + struct iovec iov = { + .iov_base = mem, + .iov_len = size, + }; + size_t cur, total, transferred; + char *old, *new; + int fds[2]; + char buf; + + old = malloc(size); + new = malloc(size); + + /* Backup the original content. */ + memcpy(old, mem, size); + + if (pipe(fds) < 0) + return -errno; + + /* Trigger a read-only pin. */ + transferred = vmsplice(fds[1], &iov, 1, 0); + if (transferred < 0) + return -errno; + if (transferred == 0) + return -EINVAL; + + /* Unmap it from our page tables. */ + if (munmap(mem, size) < 0) + return -errno; + + /* Wait until the parent modified it. */ + write(comm_pipes->child_ready[1], "0", 1); + while (read(comm_pipes->parent_ready[0], &buf, 1) != 1) + ; + + /* See if we still read the old values via the pipe. */ + for (total = 0; total < transferred; total += cur) { + cur = read(fds[0], new + total, transferred - total); + if (cur < 0) + return -errno; + } + + return memcmp(old, new, transferred); +} + +typedef int (*child_fn)(char *mem, size_t size, struct comm_pipes *comm_pipes); + +static void do_test_cow_in_parent(char *mem, size_t size, child_fn fn) +{ + struct comm_pipes comm_pipes; + char buf; + int ret; + + ret = setup_comm_pipes(&comm_pipes); + if (ret) { + ksft_test_result_fail("pipe() failed\n"); + return; + } + + ret = fork(); + if (ret < 0) { + ksft_test_result_fail("fork() failed\n"); + goto close_comm_pipes; + } else if (!ret) { + exit(fn(mem, size, &comm_pipes)); + } + + while (read(comm_pipes.child_ready[0], &buf, 1) != 1) + ; + /* Modify the page. */ + memset(mem, 0xff, size); + write(comm_pipes.parent_ready[1], "0", 1); + + wait(&ret); + if (WIFEXITED(ret)) + ret = WEXITSTATUS(ret); + else + ret = -EINVAL; + + ksft_test_result(!ret, "No leak from parent into child\n"); +close_comm_pipes: + close_comm_pipes(&comm_pipes); +} + +static void test_cow_in_parent(char *mem, size_t size) +{ + do_test_cow_in_parent(mem, size, child_memcmp_fn); +} + +static void test_vmsplice_in_child(char *mem, size_t size) +{ + do_test_cow_in_parent(mem, size, child_vmsplice_memcmp_fn); +} + +static void do_test_vmsplice_in_parent(char *mem, size_t size, + bool before_fork) +{ + struct iovec iov = { + .iov_base = mem, + .iov_len = size, + }; + size_t cur, total, transferred; + struct comm_pipes comm_pipes; + char *old, *new; + int ret, fds[2]; + char buf; + + old = malloc(size); + new = malloc(size); + + memcpy(old, mem, size); + + ret = setup_comm_pipes(&comm_pipes); + if (ret) { + ksft_test_result_fail("pipe() failed\n"); + goto free; + } + + if (pipe(fds) < 0) { + ksft_test_result_fail("pipe() failed\n"); + goto close_comm_pipes; + } + + if (before_fork) { + transferred = vmsplice(fds[1], &iov, 1, 0); + if (transferred <= 0) { + ksft_test_result_fail("vmsplice() failed\n"); + goto close_pipe; + } + } + + ret = fork(); + if (ret < 0) { + ksft_test_result_fail("fork() failed\n"); + goto close_pipe; + } else if (!ret) { + write(comm_pipes.child_ready[1], "0", 1); + while (read(comm_pipes.parent_ready[0], &buf, 1) != 1) + ; + /* Modify page content in the child. */ + memset(mem, 0xff, size); + exit(0); + } + + if (!before_fork) { + transferred = vmsplice(fds[1], &iov, 1, 0); + if (transferred <= 0) { + ksft_test_result_fail("vmsplice() failed\n"); + wait(&ret); + goto close_pipe; + } + } + + while (read(comm_pipes.child_ready[0], &buf, 1) != 1) + ; + if (munmap(mem, size) < 0) { + ksft_test_result_fail("munmap() failed\n"); + goto close_pipe; + } + write(comm_pipes.parent_ready[1], "0", 1); + + /* Wait until the child is done writing. */ + wait(&ret); + if (!WIFEXITED(ret)) { + ksft_test_result_fail("wait() failed\n"); + goto close_pipe; + } + + /* See if we still read the old values. */ + for (total = 0; total < transferred; total += cur) { + cur = read(fds[0], new + total, transferred - total); + if (cur < 0) { + ksft_test_result_fail("read() failed\n"); + goto close_pipe; + } + } + + ksft_test_result(!memcmp(old, new, transferred), + "No leak from child into parent\n"); +close_pipe: + close(fds[0]); + close(fds[1]); +close_comm_pipes: + close_comm_pipes(&comm_pipes); +free: + free(old); + free(new); +} + +static void test_vmsplice_before_fork(char *mem, size_t size) +{ + do_test_vmsplice_in_parent(mem, size, true); +} + +static void test_vmsplice_after_fork(char *mem, size_t size) +{ + do_test_vmsplice_in_parent(mem, size, false); +} + +typedef void (*test_fn)(char *mem, size_t size); + +static void do_run_with_base_page(test_fn fn, bool swapout) +{ + char *mem; + int ret; + + mem = mmap(NULL, pagesize, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (mem == MAP_FAILED) { + ksft_test_result_fail("mmap() failed\n"); + return; + } + + ret = madvise(mem, pagesize, MADV_NOHUGEPAGE); + /* Ignore if not around on a kernel. */ + if (ret && errno != EINVAL) { + ksft_test_result_fail("MADV_NOHUGEPAGE failed\n"); + goto munmap; + } + + /* Populate a base page. */ + memset(mem, 0, pagesize); + + if (swapout) { + madvise(mem, pagesize, MADV_PAGEOUT); + if (!pagemap_is_swapped(pagemap_fd, mem)) { + ksft_test_result_skip("MADV_PAGEOUT did not work, is swap enabled?\n"); + goto munmap; + } + } + + fn(mem, pagesize); +munmap: + munmap(mem, pagesize); +} + +static void run_with_base_page(test_fn fn, const char *desc) +{ + ksft_print_msg("[RUN] %s ... with base page\n", desc); + do_run_with_base_page(fn, false); +} + +static void run_with_base_page_swap(test_fn fn, const char *desc) +{ + ksft_print_msg("[RUN] %s ... with swapped out base page\n", desc); + do_run_with_base_page(fn, true); +} + +struct test_case { + const char *desc; + test_fn fn; +}; + +static const struct test_case test_cases[] = { + /* + * Basic COW tests for fork() without any GUP. If we miss to break COW, + * either the child can observe modifications by the parent or the + * other way around. + */ + { + "Basic COW after fork()", + test_cow_in_parent, + }, + /* + * vmsplice() [R/O GUP] + unmap in the child; modify in the parent. If + * we miss to break COW, the child observes modifications by the parent. + * This is CVE-2020-29374 reported by Jann Horn. + */ + { + "vmsplice() + unmap in child", + test_vmsplice_in_child + }, + /* + * vmsplice() [R/O GUP] in parent before fork(), unmap in parent after + * fork(); modify in the child. If we miss to break COW, the parent + * observes modifications by the child. + */ + { + "vmsplice() before fork(), unmap in parent after fork()", + test_vmsplice_before_fork, + }, + /* + * vmsplice() [R/O GUP] + unmap in parent after fork(); modify in the + * child. If we miss to break COW, the parent observes modifications by + * the child. + */ + { + "vmsplice() + unmap in parent after fork()", + test_vmsplice_after_fork, + }, +}; + +static void run_test_case(struct test_case const *test_case) +{ + run_with_base_page(test_case->fn, test_case->desc); + run_with_base_page_swap(test_case->fn, test_case->desc); +} + +static void run_test_cases(void) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(test_cases); i++) + run_test_case(&test_cases[i]); +} + +int main(int argc, char **argv) +{ + int nr_test_cases = ARRAY_SIZE(test_cases); + int err; + + pagesize = getpagesize(); + + ksft_print_header(); + ksft_set_plan(nr_test_cases * 2); + + pagemap_fd = open("/proc/self/pagemap", O_RDONLY); + if (pagemap_fd < 0) + ksft_exit_fail_msg("opening pagemap failed\n"); + + run_test_cases(); + + err = ksft_get_fail_cnt(); + if (err) + ksft_exit_fail_msg("%d out of %d tests failed\n", + err, ksft_test_num()); + return ksft_exit_pass(); +} diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh index e780e76c26b8..af59380bc254 100755 --- a/tools/testing/selftests/vm/run_vmtests.sh +++ b/tools/testing/selftests/vm/run_vmtests.sh @@ -197,4 +197,7 @@ fi run_test ./soft-dirty +# COW tests for anonymous memory +run_test ./anon_cow + exit $exitcode diff --git a/tools/testing/selftests/vm/vm_util.c b/tools/testing/selftests/vm/vm_util.c index b58ab11a7a30..6456027e1985 100644 --- a/tools/testing/selftests/vm/vm_util.c +++ b/tools/testing/selftests/vm/vm_util.c @@ -28,6 +28,13 @@ bool pagemap_is_softdirty(int fd, char *start) return entry & 0x0080000000000000ull; } +bool pagemap_is_swapped(int fd, char *start) +{ + uint64_t entry = pagemap_get_entry(fd, start); + + return entry & 0x4000000000000000ull; +} + void clear_softdirty(void) { int ret; diff --git a/tools/testing/selftests/vm/vm_util.h b/tools/testing/selftests/vm/vm_util.h index 2e512bd57ae1..bb8ec8d69623 100644 --- a/tools/testing/selftests/vm/vm_util.h +++ b/tools/testing/selftests/vm/vm_util.h @@ -4,6 +4,7 @@ uint64_t pagemap_get_entry(int fd, char *start); bool pagemap_is_softdirty(int fd, char *start); +bool pagemap_is_swapped(int fd, char *start); void clear_softdirty(void); uint64_t read_pmd_pagesize(void); uint64_t check_huge(void *addr);
Let's start adding tests for our COW handling of anonymous memory. We'll focus on basic tests that we can achieve without additional libraries or gup_test extensions. We'll add THP and hugetlb tests separately. Signed-off-by: David Hildenbrand <david@redhat.com> --- tools/testing/selftests/vm/.gitignore | 1 + tools/testing/selftests/vm/Makefile | 4 +- tools/testing/selftests/vm/anon_cow.c | 401 ++++++++++++++++++++++ tools/testing/selftests/vm/run_vmtests.sh | 3 + tools/testing/selftests/vm/vm_util.c | 7 + tools/testing/selftests/vm/vm_util.h | 1 + 6 files changed, 416 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/vm/anon_cow.c