diff options
Diffstat (limited to 'tests/sys/vm/shared_shadow_inval_test.c')
| -rw-r--r-- | tests/sys/vm/shared_shadow_inval_test.c | 435 |
1 files changed, 435 insertions, 0 deletions
diff --git a/tests/sys/vm/shared_shadow_inval_test.c b/tests/sys/vm/shared_shadow_inval_test.c new file mode 100644 index 000000000000..761a7ce16cf0 --- /dev/null +++ b/tests/sys/vm/shared_shadow_inval_test.c @@ -0,0 +1,435 @@ +/* + * Copyright (c) 2021 Dell Inc. or its subsidiaries. All Rights Reserved. + * Copyright (c) 2022 The FreeBSD Foundation + * + * Portions of this software were developed by Mark Johnston under sponsorship + * from the FreeBSD Foundation. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +/* + * Test behavior when a mapping of a shared shadow vm object is + * invalidated by COW from another mapping. In particular, when + * minherit(INHERT_SHARE) is applied to a COW mapping, a subsequently + * forked child process will share the parent's shadow object. Thus, + * pages already mapped into one sharing process may be written from + * another, triggering a copy into the shadow object. The VM system + * expects that a fully shadowed page is unmapped, but at one point the + * use of a shared shadow object could break this invariant. + * + * This is a regression test for an issue isolated by rlibby@FreeBSD.org + * from an issue detected by stress2's collapse.sh by jeff@FreeBSD.org. + * The issue became CVE-2021-29626. + * + * This file is written as an ATF test suite but may be compiled as a + * standalone program with -DSTANDALONE (and optionally -DDEBUG). + */ + +#include <sys/param.h> +#include <sys/mman.h> +#include <sys/procctl.h> +#include <sys/resource.h> +#include <sys/sysctl.h> +#include <sys/wait.h> + +#include <machine/atomic.h> + +#include <err.h> +#include <errno.h> +#include <stdbool.h> +#include <stddef.h> +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> + +#ifdef STANDALONE +#define ATF_REQUIRE(x) do { \ + if (!(x)) \ + errx(1, "%s", #x); \ +} while (0) +#else +#include <atf-c.h> +#endif + +#ifdef DEBUG +#define dprintf(...) printf(__VA_ARGS__) +#else +#define dprintf(...) +#endif + +#define DEPTH 5 + +#define FLAG_COLLAPSE 0x1 +#define FLAG_BLOCK_XFER 0x2 +#define FLAG_FULLMOD 0x4 +#define FLAG_MASK (FLAG_COLLAPSE | FLAG_BLOCK_XFER | FLAG_FULLMOD) + +struct shared_state { + void *p; + size_t len; + size_t modlen; + size_t pagesize; + bool collapse; + bool block_xfer; + bool lazy_cow; + bool okay; + volatile bool exiting[DEPTH]; + volatile bool exit; + volatile bool p3_did_write; +}; + +/* + * Program flow. There are three or four processes that are descendants + * of the process running the test (P0), where arrows go from parents to + * children, and thicker arrows indicate sharing a certain memory region + * without COW semantics: + * P0 -> P1 -> P2 => P3 + * \=> P4 + * The main idea is that P1 maps a memory region, and that region is + * shared with P2/P3, but with COW semantics. When P3 modifies the + * memory, P2 ought to see that modification. P4 optionally exists to + * defeat a COW optimization. + */ + +#define child_err(...) do { \ + ss->exit = true; \ + err(1, __VA_ARGS__); \ +} while (0) + +#define child_errx(...) do { \ + ss->exit = true; \ + errx(1, __VA_ARGS__); \ +} while (0) + +#define SLEEP_TIME_US 1000 + +static void child(struct shared_state *ss, int depth); + +static pid_t +child_fork(struct shared_state *ss, int depth) +{ + pid_t pid = fork(); + if (pid == -1) + child_err("fork"); + else if (pid == 0) + child(ss, depth); + return pid; +} + +static void +child_fault(struct shared_state *ss) +{ + size_t i; + + for (i = 0; i < ss->len; i += ss->pagesize) + (void)((volatile char *)ss->p)[i]; +} + +static void +child_write(struct shared_state *ss, int val, size_t len) +{ + size_t i; + + for (i = 0; i < len; i += ss->pagesize) + ((int *)ss->p)[i / sizeof(int)] = val; + atomic_thread_fence_rel(); +} + +static void +child_wait_p3_write(struct shared_state *ss) +{ + while (!ss->p3_did_write) { + if (ss->exit) + exit(1); + usleep(SLEEP_TIME_US); + } + atomic_thread_fence_acq(); +} + +static void +child_verify(struct shared_state *ss, int depth, int newval, int oldval) +{ + size_t i; + int expectval, foundval; + + for (i = 0; i < ss->len; i += ss->pagesize) { + expectval = i < ss->modlen ? newval : oldval; + foundval = ((int *)ss->p)[i / sizeof(int)]; + if (foundval == expectval) + continue; + child_errx("P%d saw %d but expected %d, %d was the old value", + depth, foundval, expectval, oldval); + } +} + +static void +child(struct shared_state *ss, int depth) +{ + pid_t mypid, oldval, pid; + + if (depth < 1 || depth >= DEPTH) + child_errx("Bad depth %d", depth); + mypid = getpid(); + dprintf("P%d (pid %d) started\n", depth, mypid); + switch (depth) { + case 1: + /* Shared memory undergoing test. */ + ss->p = mmap(NULL, ss->len, PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_ANON, -1, 0); + if (ss->p == MAP_FAILED) + child_err("mmap"); + + /* P1 stamps the shared memory. */ + child_write(ss, mypid, ss->len); + if (!ss->lazy_cow) { + if (mlock(ss->p, ss->len) == -1) + child_err("mlock"); + if (mprotect(ss->p, ss->len, PROT_READ) == -1) + child_err("mprotect"); + } + if (ss->block_xfer) { + /* + * P4 is forked so that its existence blocks a page COW + * path where the page is simply transferred between + * objects, rather than being copied. + */ + child_fork(ss, 4); + } + /* + * P1 specifies that modifications from its child processes not + * be shared with P1. Child process reads can be serviced from + * pages in P1's object, but writes must be COW'd. + */ + if (minherit(ss->p, ss->len, INHERIT_COPY) != 0) + child_err("minherit"); + /* Fork P2. */ + child_fork(ss, depth + 1); + /* P1 and P4 wait for P3's writes before exiting. */ + child_wait_p3_write(ss); + child_verify(ss, depth, mypid, mypid); + if (!ss->collapse) { + /* Hang around to prevent collapse. */ + while (!ss->exit) + usleep(SLEEP_TIME_US); + } + /* Exit so the P2 -> P1/P4 shadow chain can collapse. */ + break; + case 2: + /* + * P2 now specifies that modifications from its child processes + * be shared. P2 and P3 will share a shadow object. + */ + if (minherit(ss->p, ss->len, INHERIT_SHARE) != 0) + child_err("minherit"); + + /* + * P2 faults a page in P1's object before P1 exits and the + * shadow chain is collapsed. This may be redundant if the + * (read-only) mappings were copied by fork(), but it doesn't + * hurt. + */ + child_fault(ss); + oldval = atomic_load_acq_int(ss->p); + + /* Fork P3. */ + pid = child_fork(ss, depth + 1); + if (ss->collapse) { + /* Wait for P1 and P4 to exit, triggering collapse. */ + while (!ss->exiting[1] || + (ss->block_xfer && !ss->exiting[4])) + usleep(SLEEP_TIME_US); + /* + * This is racy, just guess at how long it may take + * them to finish exiting. + */ + usleep(100 * 1000); + } + /* P2 waits for P3's modification. */ + child_wait_p3_write(ss); + child_verify(ss, depth, pid, oldval); + ss->okay = true; + ss->exit = true; + break; + case 3: + /* + * Use mlock()+mprotect() to trigger the COW. This + * exercises a different COW handler than the one used + * for lazy faults. + */ + if (!ss->lazy_cow) { + if (mlock(ss->p, ss->len) == -1) + child_err("mlock"); + if (mprotect(ss->p, ss->len, PROT_READ | PROT_WRITE) == + -1) + child_err("mprotect"); + } + + /* + * P3 writes the memory. A page is faulted into the shared + * P2/P3 shadow object. P2's mapping of the page in P1's + * object must now be shot down, or else P2 will wrongly + * continue to have that page mapped. + */ + child_write(ss, mypid, ss->modlen); + ss->p3_did_write = true; + dprintf("P3 (pid %d) wrote its pid\n", mypid); + break; + case 4: + /* Just hang around until P3 is done writing. */ + oldval = atomic_load_acq_int(ss->p); + child_wait_p3_write(ss); + child_verify(ss, depth, oldval, oldval); + break; + default: + child_errx("Bad depth %d", depth); + } + + dprintf("P%d (pid %d) exiting\n", depth, mypid); + ss->exiting[depth] = true; + exit(0); +} + +static void +do_one_shared_shadow_inval(bool lazy_cow, size_t pagesize, size_t len, + unsigned int flags) +{ + struct shared_state *ss; + pid_t pid; + int status; + + pid = getpid(); + + dprintf("P0 (pid %d) %s(collapse=%d, block_xfer=%d, full_mod=%d)\n", + pid, __func__, (int)collapse, (int)block_xfer, (int)full_mod); + + ATF_REQUIRE(procctl(P_PID, pid, PROC_REAP_ACQUIRE, NULL) == 0); + + /* Shared memory for coordination. */ + ss = mmap(NULL, sizeof(*ss), PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_ANON, -1, 0); + ATF_REQUIRE(ss != MAP_FAILED); + + ss->len = len; + ss->modlen = (flags & FLAG_FULLMOD) ? ss->len : ss->len / 2; + ss->pagesize = pagesize; + ss->collapse = (flags & FLAG_COLLAPSE) != 0; + ss->block_xfer = (flags & FLAG_BLOCK_XFER) != 0; + ss->lazy_cow = lazy_cow; + + pid = fork(); + ATF_REQUIRE(pid != -1); + if (pid == 0) + child(ss, 1); + + /* Wait for all descendants to exit. */ + do { + pid = wait(&status); + ATF_REQUIRE(WIFEXITED(status)); + } while (pid != -1 || errno != ECHILD); + + atomic_thread_fence_acq(); + ATF_REQUIRE(ss->okay); + + ATF_REQUIRE(munmap(ss, sizeof(*ss)) == 0); + ATF_REQUIRE(procctl(P_PID, getpid(), PROC_REAP_RELEASE, NULL) == 0); +} + +static void +do_shared_shadow_inval(bool lazy_cow) +{ + size_t largepagesize, pagesize, pagesizes[MAXPAGESIZES], sysctllen; + + sysctllen = sizeof(pagesizes); + ATF_REQUIRE(sysctlbyname("hw.pagesizes", pagesizes, &sysctllen, NULL, + 0) == 0); + ATF_REQUIRE(sysctllen >= sizeof(size_t)); + + pagesize = pagesizes[0]; + largepagesize = MAXPAGESIZES >= 2 && + sysctllen >= 2 * sizeof(size_t) && pagesizes[1] != 0 ? + pagesizes[1] : 2 * 1024 * 1024; + + for (unsigned int i = 0; i <= FLAG_MASK; i++) { + do_one_shared_shadow_inval(lazy_cow, pagesize, + pagesize, i); + do_one_shared_shadow_inval(lazy_cow, pagesize, + 2 * pagesize, i); + do_one_shared_shadow_inval(lazy_cow, pagesize, + largepagesize - pagesize, i); + do_one_shared_shadow_inval(lazy_cow, pagesize, + largepagesize, i); + do_one_shared_shadow_inval(lazy_cow, pagesize, + largepagesize + pagesize, i); + } +} + +static void +do_shared_shadow_inval_eager(void) +{ + struct rlimit rl; + + rl.rlim_cur = rl.rlim_max = RLIM_INFINITY; + ATF_REQUIRE(setrlimit(RLIMIT_MEMLOCK, &rl) == 0); + + do_shared_shadow_inval(false); +} + +static void +do_shared_shadow_inval_lazy(void) +{ + do_shared_shadow_inval(true); +} + +#ifdef STANDALONE +int +main(void) +{ + do_shared_shadow_inval_lazy(); + do_shared_shadow_inval_eager(); + printf("pass\n"); +} +#else +ATF_TC_WITHOUT_HEAD(shared_shadow_inval__lazy_cow); +ATF_TC_BODY(shared_shadow_inval__lazy_cow, tc) +{ + do_shared_shadow_inval_lazy(); +} + +ATF_TC(shared_shadow_inval__eager_cow); +ATF_TC_HEAD(shared_shadow_inval__eager_cow, tc) +{ + /* Needed to raise the mlock() limit. */ + atf_tc_set_md_var(tc, "require.user", "root"); +} +ATF_TC_BODY(shared_shadow_inval__eager_cow, tc) +{ + do_shared_shadow_inval_eager(); +} + +ATF_TP_ADD_TCS(tp) +{ + ATF_TP_ADD_TC(tp, shared_shadow_inval__lazy_cow); + ATF_TP_ADD_TC(tp, shared_shadow_inval__eager_cow); + return (atf_no_error()); +} +#endif /* !STANDALONE */ |