The return code for attempting to execute a directory has always been EACCES. Adjust the S_ISDIR exec test to reflect the old errno instead of the general EISDIR for other kinds of "open" attempts on directories.

Reported-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/lkml/20200813151305.6191993b@why Fixes: 633fb6ac3980 ("exec: move S_ISREG() check earlier") Signed-off-by: Kees Cook keescook@chromium.org --- fs/namei.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c index 2112e578dccc..e99e2a9da0f7 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2849,8 +2849,10 @@ static int may_open(const struct path *path, int acc_mode, int flag) case S_IFLNK: return -ELOOP; case S_IFDIR: - if (acc_mode & (MAY_WRITE | MAY_EXEC)) + if (acc_mode & MAY_WRITE) return -EISDIR; + if (acc_mode & MAY_EXEC) + return -EACCES; break; case S_IFBLK: case S_IFCHR:

Make sure execve() returns the expected errno values for non-regular files.

Signed-off-by: Kees Cook keescook@chromium.org --- tools/testing/selftests/exec/.gitignore | 1 + tools/testing/selftests/exec/Makefile | 5 +- tools/testing/selftests/exec/non-regular.c | 196 +++++++++++++++++++++ 3 files changed, 200 insertions(+), 2 deletions(-) create mode 100755 tools/testing/selftests/exec/non-regular.c

diff --git a/tools/testing/selftests/exec/.gitignore b/tools/testing/selftests/exec/.gitignore index 94b02a18f230..344a99c6da1b 100644 --- a/tools/testing/selftests/exec/.gitignore +++ b/tools/testing/selftests/exec/.gitignore @@ -10,3 +10,4 @@ execveat.denatured /recursion-depth xxxxxxxx* pipe +S_I*.test diff --git a/tools/testing/selftests/exec/Makefile b/tools/testing/selftests/exec/Makefile index 4453b8f8def3..0a13b110c1e6 100644 --- a/tools/testing/selftests/exec/Makefile +++ b/tools/testing/selftests/exec/Makefile @@ -3,7 +3,7 @@ CFLAGS = -Wall CFLAGS += -Wno-nonnull CFLAGS += -D_GNU_SOURCE

-TEST_PROGS := binfmt_script +TEST_PROGS := binfmt_script non-regular TEST_GEN_PROGS := execveat TEST_GEN_FILES := execveat.symlink execveat.denatured script subdir pipe # Makefile is a run-time dependency, since it's accessed by the execveat test @@ -11,7 +11,8 @@ TEST_FILES := Makefile

TEST_GEN_PROGS += recursion-depth

-EXTRA_CLEAN := $(OUTPUT)/subdir.moved $(OUTPUT)/execveat.moved $(OUTPUT)/xxxxx* +EXTRA_CLEAN := $(OUTPUT)/subdir.moved $(OUTPUT)/execveat.moved $(OUTPUT)/xxxxx* \ + $(OUTPUT)/S_I*.test

include ../lib.mk

diff --git a/tools/testing/selftests/exec/non-regular.c b/tools/testing/selftests/exec/non-regular.c new file mode 100755 index 000000000000..cd3a34aca93e --- /dev/null +++ b/tools/testing/selftests/exec/non-regular.c @@ -0,0 +1,196 @@ +// SPDX-License-Identifier: GPL-2.0+ +#include <errno.h> +#include <fcntl.h> +#include <stdio.h> +#include <string.h> +#include <unistd.h> +#include <sys/socket.h> +#include <sys/stat.h> +#include <sys/sysmacros.h> +#include <sys/types.h> + +#include "../kselftest_harness.h" + +/* Remove a file, ignoring the result if it didn't exist. */ +void rm(struct __test_metadata *_metadata, const char *pathname, + int is_dir) +{ + int rc; + + if (is_dir) + rc = rmdir(pathname); + else + rc = unlink(pathname); + + if (rc < 0) { + ASSERT_EQ(errno, ENOENT) { + TH_LOG("Not ENOENT: %s", pathname); + } + } else { + ASSERT_EQ(rc, 0) { + TH_LOG("Failed to remove: %s", pathname); + } + } +} + +FIXTURE(file) { + char *pathname; + int is_dir; +}; + +FIXTURE_VARIANT(file) +{ + const char *name; + int expected; + int is_dir; + void (*setup)(struct __test_metadata *_metadata, + FIXTURE_DATA(file) *self, + const FIXTURE_VARIANT(file) *variant); + int major, minor, mode; /* for mknod() */ +}; + +void setup_link(struct __test_metadata *_metadata, + FIXTURE_DATA(file) *self, + const FIXTURE_VARIANT(file) *variant) +{ + const char * const paths[] = { + "/bin/true", + "/usr/bin/true", + }; + int i; + + for (i = 0; i < ARRAY_SIZE(paths); i++) { + if (access(paths[i], X_OK) == 0) { + ASSERT_EQ(symlink(paths[i], self->pathname), 0); + return; + } + } + ASSERT_EQ(1, 0) { + TH_LOG("Could not find viable 'true' binary"); + } +} + +FIXTURE_VARIANT_ADD(file, S_IFLNK) +{ + .name = "S_IFLNK", + .expected = ELOOP, + .setup = setup_link, +}; + +void setup_dir(struct __test_metadata *_metadata, + FIXTURE_DATA(file) *self, + const FIXTURE_VARIANT(file) *variant) +{ + ASSERT_EQ(mkdir(self->pathname, 0755), 0); +} + +FIXTURE_VARIANT_ADD(file, S_IFDIR) +{ + .name = "S_IFDIR", + .is_dir = 1, + .expected = EACCES, + .setup = setup_dir, +}; + +void setup_node(struct __test_metadata *_metadata, + FIXTURE_DATA(file) *self, + const FIXTURE_VARIANT(file) *variant) +{ + dev_t dev; + int rc; + + dev = makedev(variant->major, variant->minor); + rc = mknod(self->pathname, 0755 | variant->mode, dev); + ASSERT_EQ(rc, 0) { + if (errno == EPERM) + SKIP(return, "Please run as root; cannot mknod(%s)", + variant->name); + } +} + +FIXTURE_VARIANT_ADD(file, S_IFBLK) +{ + .name = "S_IFBLK", + .expected = EACCES, + .setup = setup_node, + /* /dev/loop0 */ + .major = 7, + .minor = 0, + .mode = S_IFBLK, +}; + +FIXTURE_VARIANT_ADD(file, S_IFCHR) +{ + .name = "S_IFCHR", + .expected = EACCES, + .setup = setup_node, + /* /dev/zero */ + .major = 1, + .minor = 5, + .mode = S_IFCHR, +}; + +void setup_fifo(struct __test_metadata *_metadata, + FIXTURE_DATA(file) *self, + const FIXTURE_VARIANT(file) *variant) +{ + ASSERT_EQ(mkfifo(self->pathname, 0755), 0); +} + +FIXTURE_VARIANT_ADD(file, S_IFIFO) +{ + .name = "S_IFIFO", + .expected = EACCES, + .setup = setup_fifo, +}; + +FIXTURE_SETUP(file) +{ + ASSERT_GT(asprintf(&self->pathname, "%s.test", variant->name), 6); + self->is_dir = variant->is_dir; + + rm(_metadata, self->pathname, variant->is_dir); + variant->setup(_metadata, self, variant); +} + +FIXTURE_TEARDOWN(file) +{ + rm(_metadata, self->pathname, self->is_dir); +} + +TEST_F(file, exec_errno) +{ + char * const argv[2] = { (char * const)self->pathname, NULL }; + + EXPECT_LT(execv(argv[0], argv), 0); + EXPECT_EQ(errno, variant->expected); +} + +/* S_IFSOCK */ +FIXTURE(sock) +{ + int fd; +}; + +FIXTURE_SETUP(sock) +{ + self->fd = socket(AF_INET, SOCK_STREAM, 0); + ASSERT_GE(self->fd, 0); +} + +FIXTURE_TEARDOWN(sock) +{ + if (self->fd >= 0) + ASSERT_EQ(close(self->fd), 0); +} + +TEST_F(sock, exec_errno) +{ + char * const argv[2] = { " magic socket ", NULL }; + char * const envp[1] = { NULL }; + + EXPECT_LT(fexecve(self->fd, argv, envp), 0); + EXPECT_EQ(errno, EACCES); +} + +TEST_HARNESS_MAIN