| Message ID | 20220729061504.744140-1-jeffxu@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
Hi Shuah Khan I will continue Daniel Verkamp's work on this patch. Could you please take a look at the new patch set I sent to see if all your comments are addressed ? Much appreciated. Best Regards, Jeff. On Thu, Jul 28, 2022 at 11:15 PM Jeff Xu <jeffxu@google.com> wrote: > > From: Daniel Verkamp <dverkamp@chromium.org> > > Basic tests to ensure that user/group/other execute bits cannot be > changed after applying F_SEAL_EXEC to a memfd. > > Co-developed-by: Jeff Xu <jeffxu@google.com> > Signed-off-by: Jeff Xu <jeffxu@google.com> > Signed-off-by: Daniel Verkamp <dverkamp@chromium.org> > --- > tools/testing/selftests/memfd/memfd_test.c | 129 ++++++++++++++++++++- > 1 file changed, 128 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c > index 94df2692e6e4..1d7e7b36bbdd 100644 > --- a/tools/testing/selftests/memfd/memfd_test.c > +++ b/tools/testing/selftests/memfd/memfd_test.c > @@ -28,12 +28,44 @@ > #define MFD_DEF_SIZE 8192 > #define STACK_SIZE 65536 > > +#ifndef F_SEAL_EXEC > +#define F_SEAL_EXEC 0x0020 > +#endif > + > +#ifndef MAX_PATH > +#define MAX_PATH 256 > +#endif > + > /* > * 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[MAX_PATH]; > + int size; > + ssize_t nbytes; > + > + size = snprintf(buf1, MAX_PATH, "/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 +130,14 @@ static unsigned int mfd_assert_get_seals(int fd) > > static void mfd_assert_has_seals(int fd, unsigned int seals) > { > + char buf[MAX_PATH]; > + int nbytes; > unsigned int s; > + fd2name(fd, buf, MAX_PATH); > > 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 +629,64 @@ static void mfd_fail_grow_write(int fd) > } > } > > +static void mfd_assert_mode(int fd, int mode) > +{ > + struct stat st; > + char buf[MAX_PATH]; > + int nbytes; > + > + fd2name(fd, buf, MAX_PATH); > + > + 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[MAX_PATH]; > + int nbytes; > + > + fd2name(fd, buf, MAX_PATH); > + > + 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[MAX_PATH]; > + int nbytes; > + > + fd2name(fd, buf, MAX_PATH); > + > + 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 +973,39 @@ 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 +1185,7 @@ 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", ""); > -- > 2.37.1.455.g008518b4e5-goog >
diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c index 94df2692e6e4..1d7e7b36bbdd 100644 --- a/tools/testing/selftests/memfd/memfd_test.c +++ b/tools/testing/selftests/memfd/memfd_test.c @@ -28,12 +28,44 @@ #define MFD_DEF_SIZE 8192 #define STACK_SIZE 65536 +#ifndef F_SEAL_EXEC +#define F_SEAL_EXEC 0x0020 +#endif + +#ifndef MAX_PATH +#define MAX_PATH 256 +#endif + /* * 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[MAX_PATH]; + int size; + ssize_t nbytes; + + size = snprintf(buf1, MAX_PATH, "/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 +130,14 @@ static unsigned int mfd_assert_get_seals(int fd) static void mfd_assert_has_seals(int fd, unsigned int seals) { + char buf[MAX_PATH]; + int nbytes; unsigned int s; + fd2name(fd, buf, MAX_PATH); 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 +629,64 @@ static void mfd_fail_grow_write(int fd) } } +static void mfd_assert_mode(int fd, int mode) +{ + struct stat st; + char buf[MAX_PATH]; + int nbytes; + + fd2name(fd, buf, MAX_PATH); + + 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[MAX_PATH]; + int nbytes; + + fd2name(fd, buf, MAX_PATH); + + 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[MAX_PATH]; + int nbytes; + + fd2name(fd, buf, MAX_PATH); + + 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 +973,39 @@ 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 +1185,7 @@ 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", "");