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selftests/memfd: add tests for F_SEAL_EXEC
Basic tests to ensure that user/group/other execute bits cannot be changed after applying F_SEAL_EXEC to a memfd. Link: https://lkml.kernel.org/r/20221215001205.51969-3-jeffxu@google.com Signed-off-by: Daniel Verkamp <dverkamp@chromium.org> Co-developed-by: Jeff Xu <jeffxu@google.com> Signed-off-by: Jeff Xu <jeffxu@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Cc: David Herrmann <dh.herrmann@gmail.com> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jann Horn <jannh@google.com> Cc: Jorge Lucangeli Obes <jorgelo@chromium.org> Cc: kernel test robot <lkp@intel.com> Cc: Shuah Khan <skhan@linuxfoundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -28,12 +28,38 @@
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#define MFD_DEF_SIZE 8192
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#define STACK_SIZE 65536
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#define F_SEAL_EXEC 0x0020
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/*
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* Default is not to test hugetlbfs
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*/
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static size_t mfd_def_size = MFD_DEF_SIZE;
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static const char *memfd_str = MEMFD_STR;
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static ssize_t fd2name(int fd, char *buf, size_t bufsize)
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{
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char buf1[PATH_MAX];
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int size;
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ssize_t nbytes;
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size = snprintf(buf1, PATH_MAX, "/proc/self/fd/%d", fd);
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if (size < 0) {
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printf("snprintf(%d) failed on %m\n", fd);
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abort();
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}
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/*
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* reserver one byte for string termination.
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*/
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nbytes = readlink(buf1, buf, bufsize-1);
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if (nbytes == -1) {
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printf("readlink(%s) failed %m\n", buf1);
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abort();
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}
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buf[nbytes] = '\0';
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return nbytes;
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}
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static int mfd_assert_new(const char *name, loff_t sz, unsigned int flags)
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{
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int r, fd;
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@ -98,11 +124,14 @@ static unsigned int mfd_assert_get_seals(int fd)
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static void mfd_assert_has_seals(int fd, unsigned int seals)
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{
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char buf[PATH_MAX];
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int nbytes;
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unsigned int s;
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fd2name(fd, buf, PATH_MAX);
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s = mfd_assert_get_seals(fd);
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if (s != seals) {
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printf("%u != %u = GET_SEALS(%d)\n", seals, s, fd);
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printf("%u != %u = GET_SEALS(%s)\n", seals, s, buf);
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abort();
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}
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}
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@ -594,6 +623,64 @@ static void mfd_fail_grow_write(int fd)
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}
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}
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static void mfd_assert_mode(int fd, int mode)
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{
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struct stat st;
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char buf[PATH_MAX];
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int nbytes;
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fd2name(fd, buf, PATH_MAX);
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if (fstat(fd, &st) < 0) {
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printf("fstat(%s) failed: %m\n", buf);
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abort();
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}
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if ((st.st_mode & 07777) != mode) {
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printf("fstat(%s) wrong file mode 0%04o, but expected 0%04o\n",
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buf, (int)st.st_mode & 07777, mode);
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abort();
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}
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}
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static void mfd_assert_chmod(int fd, int mode)
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{
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char buf[PATH_MAX];
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int nbytes;
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fd2name(fd, buf, PATH_MAX);
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if (fchmod(fd, mode) < 0) {
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printf("fchmod(%s, 0%04o) failed: %m\n", buf, mode);
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abort();
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}
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mfd_assert_mode(fd, mode);
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}
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static void mfd_fail_chmod(int fd, int mode)
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{
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struct stat st;
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char buf[PATH_MAX];
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int nbytes;
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fd2name(fd, buf, PATH_MAX);
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if (fstat(fd, &st) < 0) {
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printf("fstat(%s) failed: %m\n", buf);
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abort();
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}
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if (fchmod(fd, mode) == 0) {
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printf("fchmod(%s, 0%04o) didn't fail as expected\n",
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buf, mode);
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abort();
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}
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/* verify that file mode bits did not change */
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mfd_assert_mode(fd, st.st_mode & 07777);
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}
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static int idle_thread_fn(void *arg)
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{
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sigset_t set;
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@ -880,6 +967,39 @@ static void test_seal_resize(void)
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close(fd);
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}
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/*
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* Test SEAL_EXEC
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* Test that chmod() cannot change x bits after sealing
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*/
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static void test_seal_exec(void)
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{
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int fd;
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printf("%s SEAL-EXEC\n", memfd_str);
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fd = mfd_assert_new("kern_memfd_seal_exec",
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mfd_def_size,
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MFD_CLOEXEC | MFD_ALLOW_SEALING);
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mfd_assert_mode(fd, 0777);
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mfd_assert_chmod(fd, 0644);
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mfd_assert_has_seals(fd, 0);
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mfd_assert_add_seals(fd, F_SEAL_EXEC);
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mfd_assert_has_seals(fd, F_SEAL_EXEC);
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mfd_assert_chmod(fd, 0600);
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mfd_fail_chmod(fd, 0777);
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mfd_fail_chmod(fd, 0670);
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mfd_fail_chmod(fd, 0605);
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mfd_fail_chmod(fd, 0700);
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mfd_fail_chmod(fd, 0100);
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mfd_assert_chmod(fd, 0666);
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close(fd);
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}
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/*
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* Test sharing via dup()
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* Test that seals are shared between dupped FDs and they're all equal.
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@ -1059,6 +1179,7 @@ int main(int argc, char **argv)
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test_seal_shrink();
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test_seal_grow();
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test_seal_resize();
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test_seal_exec();
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test_share_dup("SHARE-DUP", "");
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test_share_mmap("SHARE-MMAP", "");
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