Re: [LTP] [PATCH v2 05/11] Add landlock01 test

[Andrea Cervesato via ltp <ltp@lists.linux.it>]

Hi,

On 7/11/24 05:16, Li Wang wrote:
> Hi Andrea,
>
> On Thu, Jul 11, 2024 at 2:02 AM Andrea Cervesato 
> <andrea.cervesato@suse.de> wrote:
>
>     From: Andrea Cervesato <andrea.cervesato@suse.com>
>
>     This test verifies that landlock_create_ruleset syscall fails with the
>     right error codes:
>
>     - EINVAL Unknown flags, or unknown access, or too small size
>     - E2BIG size is too big
>     - EFAULT attr was not a valid address
>     - ENOMSG Empty accesses (i.e., attr->handled_access_fs is 0)
>
>     Reviewed-by: Li Wang <liwang@redhat.com>
>     Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
>     ---
>      runtest/syscalls                                   |  2 +
>      testcases/kernel/syscalls/landlock/.gitignore      |  1 +
>      testcases/kernel/syscalls/landlock/Makefile        |  7 ++
>      testcases/kernel/syscalls/landlock/landlock01.c    | 92
>     ++++++++++++++++++++++
>      .../kernel/syscalls/landlock/landlock_common.h     | 74
>     +++++++++++++++++
>      5 files changed, 176 insertions(+)
>
>     diff --git a/runtest/syscalls b/runtest/syscalls
>     index b6cadb2df..667e419a3 100644
>     --- a/runtest/syscalls
>     +++ b/runtest/syscalls
>     @@ -684,6 +684,8 @@ kill11 kill11
>      kill12 kill12
>      kill13 kill13
>
>     +landlock01 landlock01
>     +
>      lchown01 lchown01
>      lchown01_16 lchown01_16
>      lchown02  lchown02
>     diff --git a/testcases/kernel/syscalls/landlock/.gitignore
>     b/testcases/kernel/syscalls/landlock/.gitignore
>     new file mode 100644
>     index 000000000..b69f9b94a
>     --- /dev/null
>     +++ b/testcases/kernel/syscalls/landlock/.gitignore
>     @@ -0,0 +1 @@
>     +landlock01
>     diff --git a/testcases/kernel/syscalls/landlock/Makefile
>     b/testcases/kernel/syscalls/landlock/Makefile
>     new file mode 100644
>     index 000000000..8cf1b9024
>     --- /dev/null
>     +++ b/testcases/kernel/syscalls/landlock/Makefile
>     @@ -0,0 +1,7 @@
>     +# SPDX-License-Identifier: GPL-2.0-or-later
>     +# Copyright (C) 2024 SUSE LLC Andrea Cervesato
>     <andrea.cervesato@suse.com>
>     +
>     +top_srcdir             ?= ../../../..
>     +
>     +include $(top_srcdir)/include/mk/testcases.mk <http://testcases.mk>
>     +include $(top_srcdir)/include/mk/generic_leaf_target.mk
>     <http://generic_leaf_target.mk>
>     diff --git a/testcases/kernel/syscalls/landlock/landlock01.c
>     b/testcases/kernel/syscalls/landlock/landlock01.c
>     new file mode 100644
>     index 000000000..90f338fb0
>     --- /dev/null
>     +++ b/testcases/kernel/syscalls/landlock/landlock01.c
>     @@ -0,0 +1,92 @@
>     +// SPDX-License-Identifier: GPL-2.0-or-later
>     +/*
>     + * Copyright (C) 2024 SUSE LLC Andrea Cervesato
>     <andrea.cervesato@suse.com>
>     + */
>     +
>     +/*\
>     + * [Description]
>     + *
>     + * This test verifies that landlock_create_ruleset syscall fails
>     with the right
>     + * error codes:
>     + *
>     + * - EINVAL Unknown flags, or unknown access, or too small size
>     + * - E2BIG size is too big
>     + * - EFAULT attr was not a valid address
>     + * - ENOMSG Empty accesses (i.e., attr->handled_access_fs is 0)
>     + */
>     +
>     +#include "landlock_common.h"
>     +
>     +static struct landlock_ruleset_attr *ruleset_attr;
>     +static struct landlock_ruleset_attr *null_attr;
>     +static size_t rule_size;
>     +static size_t rule_small_size;
>     +static size_t rule_big_size;
>     +
>     +static struct tcase {
>     +       struct landlock_ruleset_attr **attr;
>     +       uint64_t access_fs;
>     +       size_t *size;
>     +       uint32_t flags;
>     +       int exp_errno;
>     +       char *msg;
>     +} tcases[] = {
>     +       {&ruleset_attr, -1, &rule_size, 0, EINVAL, "Unknown access"},
>     +       {&ruleset_attr, 0, &rule_small_size, 0, EINVAL, "Size is
>     too small"},
>     +       {&ruleset_attr, 0, &rule_size, -1, EINVAL, "Unknown flags"},
>     +       {&ruleset_attr, 0, &rule_big_size, 0, E2BIG, "Size is too
>     big"},
>     +       {&null_attr,    0, &rule_size, 0, EFAULT, "Invalid attr
>     address"},
>     +       {&ruleset_attr, 0, &rule_size, 0, ENOMSG, "Empty accesses"},
>     +};
>     +
>     +static void run(unsigned int n)
>     +{
>     +       struct tcase *tc = &tcases[n];
>     +
>     +       if (*tc->attr)
>     +               (*tc->attr)->handled_access_fs = tc->access_fs;
>     +
>     +  TST_EXP_FAIL(tst_syscall(__NR_landlock_create_ruleset,
>     +                       *tc->attr, *tc->size, tc->flags),
>     +               tc->exp_errno,
>     +               "%s",
>     +               tc->msg);
>     +
>     +       if (TST_RET >= 0)
>     +               SAFE_CLOSE(TST_RET);
>     +}
>     +
>     +static void setup(void)
>     +{
>     +       verify_landlock_is_enabled();
>     +
>     +       rule_size = sizeof(struct landlock_ruleset_attr);
>     +
>     +#ifdef HAVE_STRUCT_LANDLOCK_RULESET_ATTR_HANDLED_ACCESS_NET
>     +       rule_small_size = rule_size - sizeof(uint64_t);
>
>
> This is incorrect, at least decrease 1 more number:
>  rule_small_size = rule_size - sizeof(uint64_t) - 1;
>
> But, those are quite unnecessary to add the if macro conditions,
> as the kernel code explicitly compares the minimal struct with
> handled_access_fs via:
>
>  offsetofend(typeof(ruleset_attr), handled_access_fs)
>
I usually don't look at the kernel source code to write tests, because 
for us it should be a black box that could have wrong documentation.
That's also the way we find bugs.

I would go for still using the macros, but removing 1 more byte from the 
size when handled_access_net is defined.

> (and Mickael said it should never change for backward compatibility 
> reason)
>
> So it should be just simple like:
>
> --- a/testcases/kernel/syscalls/landlock/landlock01.c
> +++ b/testcases/kernel/syscalls/landlock/landlock01.c
> @@ -62,11 +62,15 @@ static void setup(void)
>
>         rule_size = sizeof(struct landlock_ruleset_attr);
>
> -#ifdef HAVE_STRUCT_LANDLOCK_RULESET_ATTR_HANDLED_ACCESS_NET
> -       rule_small_size = rule_size - sizeof(uint64_t);
> -#else
> -       rule_small_size = rule_size - 1;
> -#endif
> +       /*
> +        * The new kernel introduces a new field 'handled_access_net' 
> in the
> +        * structure 'landlock_ruleset_attr'. However, in the function
> +        * 'landlock_create_ruleset()', it still uses the first field
> +        * 'handled_access_fs' to calculate the minimal size for backward
> +        * compatibility reason. Therefore, here test 'sizeof(__u64) - 
> 1' is
> +        * sufficient to determine the minimum size for 'rule_small_size'.
> +        */
> +       rule_small_size = sizeof(__u64) - 1;
>
>         rule_big_size = SAFE_SYSCONF(_SC_PAGESIZE) + 1;
>  }
>
>     +#else
>     +       rule_small_size = rule_size - 1;
>     +#endif
>     +
>     +       rule_big_size = SAFE_SYSCONF(_SC_PAGESIZE) + 1;
>     +}
>     +
>     +static struct tst_test test = {
>     +       .test = run,
>     +       .tcnt = ARRAY_SIZE(tcases),
>     +       .setup = setup,
>     +       .min_kver = "5.13",
>     +       .needs_root = 1,
>     +       .needs_kconfigs = (const char *[]) {
>     +               "CONFIG_SECURITY_LANDLOCK=y",
>     +               NULL
>     +       },
>     +       .bufs = (struct tst_buffers []) {
>     +               {&ruleset_attr, .size = sizeof(struct
>     landlock_ruleset_attr)},
>     +               {},
>     +       },
>     +       .caps = (struct tst_cap []) {
>     +               TST_CAP(TST_CAP_REQ, CAP_SYS_ADMIN),
>     +               {}
>     +       },
>     +};
>     diff --git a/testcases/kernel/syscalls/landlock/landlock_common.h
>     b/testcases/kernel/syscalls/landlock/landlock_common.h
>     new file mode 100644
>     index 000000000..66f8fd19a
>     --- /dev/null
>     +++ b/testcases/kernel/syscalls/landlock/landlock_common.h
>     @@ -0,0 +1,74 @@
>     +/* SPDX-License-Identifier: GPL-2.0-or-later */
>     +/*
>     + * Copyright (C) 2024 SUSE LLC Andrea Cervesato
>     <andrea.cervesato@suse.com>
>     + */
>     +
>     +#ifndef LANDLOCK_COMMON_H
>     +
>     +#include "tst_test.h"
>     +#include "lapi/prctl.h"
>     +#include "lapi/fcntl.h"
>     +#include "lapi/landlock.h"
>     +
>     +static inline void verify_landlock_is_enabled(void)
>     +{
>     +       int abi;
>     +
>     +       abi = tst_syscall(__NR_landlock_create_ruleset,
>     +               NULL, 0, LANDLOCK_CREATE_RULESET_VERSION);
>     +
>     +       if (abi < 0) {
>     +               if (errno == EOPNOTSUPP) {
>     +                       tst_brk(TCONF, "Landlock is currently
>     disabled. "
>     +                               "Please enable it either via
>     CONFIG_LSM or "
>     +                               "'lsm' kernel parameter.");
>     +               }
>     +
>     +               tst_brk(TBROK | TERRNO, "landlock_create_ruleset
>     error");
>     +       }
>     +
>     +       tst_res(TINFO, "Landlock ABI v%d", abi);
>     +}
>     +
>     +static inline void apply_landlock_rule(
>     +       struct landlock_path_beneath_attr *path_beneath_attr,
>     +       const int ruleset_fd,
>     +       const int access,
>     +       const char *path)
>     +{
>     +       path_beneath_attr->allowed_access = access;
>     +       path_beneath_attr->parent_fd = SAFE_OPEN(path, O_PATH |
>     O_CLOEXEC);
>     +
>     +       SAFE_LANDLOCK_ADD_RULE(
>     +               ruleset_fd,
>     +               LANDLOCK_RULE_PATH_BENEATH,
>     +               path_beneath_attr,
>     +               0);
>     +
>     +       SAFE_CLOSE(path_beneath_attr->parent_fd);
>     +}
>     +
>     +static inline void enforce_ruleset(const int ruleset_fd)
>     +{
>     +       SAFE_PRCTL(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
>     +       SAFE_LANDLOCK_RESTRICT_SELF(ruleset_fd, 0);
>     +}
>     +
>     +static inline void apply_landlock_layer(
>     +       struct landlock_ruleset_attr *ruleset_attr,
>     +       struct landlock_path_beneath_attr *path_beneath_attr,
>     +       const char *path,
>     +       const int access)
>     +{
>     +       int ruleset_fd;
>     +
>     +       ruleset_fd = SAFE_LANDLOCK_CREATE_RULESET(
>     +               ruleset_attr, sizeof(struct
>     landlock_ruleset_attr), 0);
>     +
>     +       apply_landlock_rule(path_beneath_attr, ruleset_fd, access,
>     path);
>     +       enforce_ruleset(ruleset_fd);
>     +
>     +       SAFE_CLOSE(ruleset_fd);
>     +}
>     +
>     +#endif
>
>     -- 
>     2.43.0
>
>
>
> -- 
> Regards,
> Li Wang

Andrea

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