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selftests/memfd: add tests for F_SEAL_EXEC

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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>
This commit is contained in:
Daniel Verkamp 2022-12-15 00:12:02 +00:00 committed by Andrew Morton
parent 6fd7353829
commit 32d118ad50
1 changed files with 122 additions and 1 deletions
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123
tools/testing/selftests/memfd/memfd_test.c
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@ -28,12 +28,38 @@
#define MFD_DEF_SIZE 8192
#define STACK_SIZE 65536
#define F_SEAL_EXEC 0x0020
/*
* Default is not to test hugetlbfs
*/
static size_t mfd_def_size = MFD_DEF_SIZE;
static const char *memfd_str = MEMFD_STR;
static ssize_t fd2name(int fd, char *buf, size_t bufsize)
{
char buf1[PATH_MAX];
int size;
ssize_t nbytes;
size = snprintf(buf1, PATH_MAX, "/proc/self/fd/%d", fd);
if (size < 0) {
printf("snprintf(%d) failed on %m\n", fd);
abort();
}
/*
* reserver one byte for string termination.
*/
nbytes = readlink(buf1, buf, bufsize-1);
if (nbytes == -1) {
printf("readlink(%s) failed %m\n", buf1);
abort();
}
buf[nbytes] = '\0';
return nbytes;
}
static int mfd_assert_new(const char *name, loff_t sz, unsigned int flags)
{
int r, fd;
@ -98,11 +124,14 @@ static unsigned int mfd_assert_get_seals(int fd)
static void mfd_assert_has_seals(int fd, unsigned int seals)
{
char buf[PATH_MAX];
int nbytes;
unsigned int s;
fd2name(fd, buf, PATH_MAX);
s = mfd_assert_get_seals(fd);
if (s != seals) {
printf("%u != %u = GET_SEALS(%d)\n", seals, s, fd);
printf("%u != %u = GET_SEALS(%s)\n", seals, s, buf);
abort();
}
}
@ -594,6 +623,64 @@ static void mfd_fail_grow_write(int fd)
}
}
static void mfd_assert_mode(int fd, int mode)
{
struct stat st;
char buf[PATH_MAX];
int nbytes;
fd2name(fd, buf, PATH_MAX);
if (fstat(fd, &st) < 0) {
printf("fstat(%s) failed: %m\n", buf);
abort();
}
if ((st.st_mode & 07777) != mode) {
printf("fstat(%s) wrong file mode 0%04o, but expected 0%04o\n",
buf, (int)st.st_mode & 07777, mode);
abort();
}
}
static void mfd_assert_chmod(int fd, int mode)
{
char buf[PATH_MAX];
int nbytes;
fd2name(fd, buf, PATH_MAX);
if (fchmod(fd, mode) < 0) {
printf("fchmod(%s, 0%04o) failed: %m\n", buf, mode);
abort();
}
mfd_assert_mode(fd, mode);
}
static void mfd_fail_chmod(int fd, int mode)
{
struct stat st;
char buf[PATH_MAX];
int nbytes;
fd2name(fd, buf, PATH_MAX);
if (fstat(fd, &st) < 0) {
printf("fstat(%s) failed: %m\n", buf);
abort();
}
if (fchmod(fd, mode) == 0) {
printf("fchmod(%s, 0%04o) didn't fail as expected\n",
buf, mode);
abort();
}
/* verify that file mode bits did not change */
mfd_assert_mode(fd, st.st_mode & 07777);
}
static int idle_thread_fn(void *arg)
{
sigset_t set;
@ -880,6 +967,39 @@ static void test_seal_resize(void)
close(fd);
}
/*
* Test SEAL_EXEC
* Test that chmod() cannot change x bits after sealing
*/
static void test_seal_exec(void)
{
int fd;
printf("%s SEAL-EXEC\n", memfd_str);
fd = mfd_assert_new("kern_memfd_seal_exec",
mfd_def_size,
MFD_CLOEXEC | MFD_ALLOW_SEALING);
mfd_assert_mode(fd, 0777);
mfd_assert_chmod(fd, 0644);
mfd_assert_has_seals(fd, 0);
mfd_assert_add_seals(fd, F_SEAL_EXEC);
mfd_assert_has_seals(fd, F_SEAL_EXEC);
mfd_assert_chmod(fd, 0600);
mfd_fail_chmod(fd, 0777);
mfd_fail_chmod(fd, 0670);
mfd_fail_chmod(fd, 0605);
mfd_fail_chmod(fd, 0700);
mfd_fail_chmod(fd, 0100);
mfd_assert_chmod(fd, 0666);
close(fd);
}
/*
* Test sharing via dup()
* Test that seals are shared between dupped FDs and they're all equal.
@ -1059,6 +1179,7 @@ int main(int argc, char **argv)
test_seal_shrink();
test_seal_grow();
test_seal_resize();
test_seal_exec();
test_share_dup("SHARE-DUP", "");
test_share_mmap("SHARE-MMAP", "");