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  3. [PATCH 0/2] exec: Add KUnit test for bprm_stack_limits()
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[PATCH 1/2] exec: Add KUnit test for bprm_stack_limits()

Kees Cook posted 2 patches 1 year, 8 months ago
[PATCH 1/2] exec: Add KUnit test for bprm_stack_limits()
Posted by Kees Cook 1 year, 8 months ago 
Since bprm_stack_limits() operates with very limited side-effects, add
it as the first exec.c KUnit test. Add to Kconfig and adjust MAINTAINERS
file to include it.

Tested on 64-bit UML:
$ tools/testing/kunit/kunit.py run exec

Signed-off-by: Kees Cook <keescook@chromium.org>
---
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-mm@kvack.org
---
 MAINTAINERS       |   2 +
 fs/Kconfig.binfmt |   8 ++++
 fs/exec.c         |  13 ++++++
 fs/exec_test.c    | 113 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 136 insertions(+)
 create mode 100644 fs/exec_test.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 7c121493f43d..845165dbb756 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8039,7 +8039,9 @@ S:	Supported
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/execve
 F:	Documentation/userspace-api/ELF.rst
 F:	fs/*binfmt_*.c
+F:	fs/Kconfig.binfmt
 F:	fs/exec.c
+F:	fs/exec_test.c
 F:	include/linux/binfmts.h
 F:	include/linux/elf.h
 F:	include/uapi/linux/binfmts.h
diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index f5693164ca9a..58657f2d9719 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -176,4 +176,12 @@ config COREDUMP
 	  certainly want to say Y here. Not necessary on systems that never
 	  need debugging or only ever run flawless code.
 
+config EXEC_KUNIT_TEST
+	bool "Build execve tests" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the exec KUnit tests, which tests boundary conditions
+	  of various aspects of the exec internals.
+
 endmenu
diff --git a/fs/exec.c b/fs/exec.c
index b3c40fbb325f..1d45e1a2d620 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -475,6 +475,15 @@ static int count_strings_kernel(const char *const *argv)
 	return i;
 }
 
+/*
+ * Calculate bprm->argmin from:
+ * - _STK_LIM
+ * - ARG_MAX
+ * - bprm->rlim_stack.rlim_cur
+ * - bprm->argc
+ * - bprm->envc
+ * - bprm->p
+ */
 static int bprm_stack_limits(struct linux_binprm *bprm)
 {
 	unsigned long limit, ptr_size;
@@ -2200,3 +2209,7 @@ static int __init init_fs_exec_sysctls(void)
 
 fs_initcall(init_fs_exec_sysctls);
 #endif /* CONFIG_SYSCTL */
+
+#ifdef CONFIG_EXEC_KUNIT_TEST
+#include "exec_test.c"
+#endif
diff --git a/fs/exec_test.c b/fs/exec_test.c
new file mode 100644
index 000000000000..32a90c6f47e7
--- /dev/null
+++ b/fs/exec_test.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <kunit/test.h>
+
+struct bprm_stack_limits_result {
+	struct linux_binprm bprm;
+	int expected_rc;
+	unsigned long expected_argmin;
+};
+
+static const struct bprm_stack_limits_result bprm_stack_limits_results[] = {
+	/* Giant values produce -E2BIG */
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = ULONG_MAX,
+	    .argc = INT_MAX, .envc = INT_MAX }, .expected_rc = -E2BIG },
+	/*
+	 * 0 rlim_stack will get raised to ARG_MAX. With 1 string pointer,
+	 * we should see p - ARG_MAX + sizeof(void *).
+	 */
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 0,
+	    .argc = 1, .envc = 0 }, .expected_argmin = ULONG_MAX - ARG_MAX + sizeof(void *)},
+	/* Validate that argc is always raised to a minimum of 1. */
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 0,
+	    .argc = 0, .envc = 0 }, .expected_argmin = ULONG_MAX - ARG_MAX + sizeof(void *)},
+	/*
+	 * 0 rlim_stack will get raised to ARG_MAX. With pointers filling ARG_MAX,
+	 * we should see -E2BIG. (Note argc is always raised to at least 1.)
+	 */
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 0,
+	    .argc = ARG_MAX / sizeof(void *), .envc = 0 }, .expected_rc = -E2BIG },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 0,
+	    .argc = 0, .envc = ARG_MAX / sizeof(void *) - 1 }, .expected_rc = -E2BIG },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 0,
+	    .argc = ARG_MAX / sizeof(void *) + 1, .envc = 0 }, .expected_rc = -E2BIG },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 0,
+	    .argc = 0, .envc = ARG_MAX / sizeof(void *) }, .expected_rc = -E2BIG },
+	/* And with one less, we see space for exactly 1 pointer. */
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 0,
+	    .argc = (ARG_MAX / sizeof(void *)) - 1, .envc = 0 },
+	  .expected_argmin = ULONG_MAX - sizeof(void *) },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 0,
+	    .argc = 0, .envc = (ARG_MAX / sizeof(void *)) - 2, },
+	  .expected_argmin = ULONG_MAX - sizeof(void *) },
+	/* If we raise rlim_stack / 4 to exactly ARG_MAX, nothing changes. */
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = ARG_MAX * 4,
+	    .argc = ARG_MAX / sizeof(void *), .envc = 0 }, .expected_rc = -E2BIG },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = ARG_MAX * 4,
+	    .argc = 0, .envc = ARG_MAX / sizeof(void *) - 1 }, .expected_rc = -E2BIG },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = ARG_MAX * 4,
+	    .argc = ARG_MAX / sizeof(void *) + 1, .envc = 0 }, .expected_rc = -E2BIG },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = ARG_MAX * 4,
+	    .argc = 0, .envc = ARG_MAX / sizeof(void *) }, .expected_rc = -E2BIG },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = ARG_MAX * 4,
+	    .argc = (ARG_MAX / sizeof(void *)) - 1, .envc = 0 },
+	  .expected_argmin = ULONG_MAX - sizeof(void *) },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = ARG_MAX * 4,
+	    .argc = 0, .envc = (ARG_MAX / sizeof(void *)) - 2, },
+	  .expected_argmin = ULONG_MAX - sizeof(void *) },
+	/* But raising it another pointer * 4 will provide space for 1 more pointer. */
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = (ARG_MAX + sizeof(void *)) * 4,
+	    .argc = ARG_MAX / sizeof(void *), .envc = 0 },
+	  .expected_argmin = ULONG_MAX - sizeof(void *) },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = (ARG_MAX + sizeof(void *)) * 4,
+	    .argc = 0, .envc = ARG_MAX / sizeof(void *) - 1 },
+	  .expected_argmin = ULONG_MAX - sizeof(void *) },
+	/* Raising rlim_stack / 4 to _STK_LIM / 4 * 3 will see more space. */
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 4 * (_STK_LIM / 4 * 3),
+	    .argc = 0, .envc = 0 },
+	  .expected_argmin = ULONG_MAX - (_STK_LIM / 4 * 3) + sizeof(void *) },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 4 * (_STK_LIM / 4 * 3),
+	    .argc = 0, .envc = 0 },
+	  .expected_argmin = ULONG_MAX - (_STK_LIM / 4 * 3) + sizeof(void *) },
+	/* But raising it any further will see no increase. */
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 4 * (_STK_LIM / 4 * 3 + sizeof(void *)),
+	    .argc = 0, .envc = 0 },
+	  .expected_argmin = ULONG_MAX - (_STK_LIM / 4 * 3) + sizeof(void *) },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 4 * (_STK_LIM / 4 *  + sizeof(void *)),
+	    .argc = 0, .envc = 0 },
+	  .expected_argmin = ULONG_MAX - (_STK_LIM / 4 * 3) + sizeof(void *) },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 4 * _STK_LIM,
+	    .argc = 0, .envc = 0 },
+	  .expected_argmin = ULONG_MAX - (_STK_LIM / 4 * 3) + sizeof(void *) },
+	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 4 * _STK_LIM,
+	    .argc = 0, .envc = 0 },
+	  .expected_argmin = ULONG_MAX - (_STK_LIM / 4 * 3) + sizeof(void *) },
+};
+
+static void exec_test_bprm_stack_limits(struct kunit *test)
+{
+	/* Double-check the constants. */
+	KUNIT_EXPECT_EQ(test, _STK_LIM, SZ_8M);
+	KUNIT_EXPECT_EQ(test, ARG_MAX, 32 * SZ_4K);
+
+	for (int i = 0; i < ARRAY_SIZE(bprm_stack_limits_results); i++) {
+		const struct bprm_stack_limits_result *result = &bprm_stack_limits_results[i];
+		struct linux_binprm bprm = result->bprm;
+		int rc;
+
+		rc = bprm_stack_limits(&bprm);
+		KUNIT_EXPECT_EQ_MSG(test, rc, result->expected_rc, "on loop %d", i);
+		KUNIT_EXPECT_EQ_MSG(test, bprm.argmin, result->expected_argmin, "on loop %d", i);
+	}
+}
+
+static struct kunit_case exec_test_cases[] = {
+	KUNIT_CASE(exec_test_bprm_stack_limits),
+	{},
+};
+
+static struct kunit_suite exec_test_suite = {
+	.name = "exec",
+	.test_cases = exec_test_cases,
+};
+
+kunit_test_suite(exec_test_suite);
-- 
2.34.1
Re: [PATCH 1/2] exec: Add KUnit test for bprm_stack_limits()
Posted by kernel test robot 1 year, 8 months ago 
Hi Kees,

kernel test robot noticed the following build errors:

[auto build test ERROR on kees/for-next/execve]
[also build test ERROR on kees/for-next/pstore kees/for-next/kspp brauner-vfs/vfs.all linus/master vfs-idmapping/for-next v6.9 next-20240520]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Kees-Cook/exec-Avoid-pathological-argc-envc-and-bprm-p-values/20240520-101851
base:   https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/execve
patch link:    https://lore.kernel.org/r/20240520021615.741800-1-keescook%40chromium.org
patch subject: [PATCH 1/2] exec: Add KUnit test for bprm_stack_limits()
config: nios2-allmodconfig (https://download.01.org/0day-ci/archive/20240520/202405202231.3Q9gWCar-lkp@intel.com/config)
compiler: nios2-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240520/202405202231.3Q9gWCar-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202405202231.3Q9gWCar-lkp@intel.com/

All errors (new ones prefixed by >>):

   nios2-linux-ld: fs/exec.o: in function `exec_test_bprm_stack_limits':
   exec.c:(.text+0x1904): undefined reference to `kunit_binary_assert_format'
>> nios2-linux-ld: exec.c:(.text+0x192c): undefined reference to `kunit_binary_assert_format'
>> nios2-linux-ld: exec.c:(.text+0x19e8): undefined reference to `__kunit_do_failed_assertion'
>> exec.c:(.text+0x19e8): relocation truncated to fit: R_NIOS2_CALL26 against `__kunit_do_failed_assertion'
   nios2-linux-ld: exec.c:(.text+0x1a28): undefined reference to `__kunit_do_failed_assertion'
   exec.c:(.text+0x1a28): relocation truncated to fit: R_NIOS2_CALL26 against `__kunit_do_failed_assertion'

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Re: [PATCH 1/2] exec: Add KUnit test for bprm_stack_limits()
Posted by kernel test robot 1 year, 8 months ago 
Hi Kees,

kernel test robot noticed the following build errors:

[auto build test ERROR on kees/for-next/execve]
[also build test ERROR on kees/for-next/pstore kees/for-next/kspp brauner-vfs/vfs.all linus/master v6.9 next-20240520]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Kees-Cook/exec-Avoid-pathological-argc-envc-and-bprm-p-values/20240520-101851
base:   https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/execve
patch link:    https://lore.kernel.org/r/20240520021615.741800-1-keescook%40chromium.org
patch subject: [PATCH 1/2] exec: Add KUnit test for bprm_stack_limits()
config: i386-randconfig-004-20240520 (https://download.01.org/0day-ci/archive/20240520/202405202157.xE9dP8fI-lkp@intel.com/config)
compiler: gcc-13 (Ubuntu 13.2.0-4ubuntu3) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240520/202405202157.xE9dP8fI-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202405202157.xE9dP8fI-lkp@intel.com/

All errors (new ones prefixed by >>):

   ld: fs/exec.o: in function `exec_test_bprm_stack_limits':
>> fs/exec_test.c:98:(.text+0xdfc): undefined reference to `kunit_binary_assert_format'
>> ld: fs/exec_test.c:98:(.text+0xe0c): undefined reference to `__kunit_do_failed_assertion'
>> ld: fs/exec_test.c:99:(.text+0xe56): undefined reference to `kunit_binary_assert_format'
   ld: fs/exec_test.c:99:(.text+0xe66): undefined reference to `__kunit_do_failed_assertion'

Kconfig warnings: (for reference only)
   WARNING: unmet direct dependencies detected for FB_IOMEM_HELPERS
   Depends on [n]: HAS_IOMEM [=y] && FB_CORE [=n]
   Selected by [m]:
   - DRM_XE_DISPLAY [=y] && HAS_IOMEM [=y] && DRM_XE [=m] && DRM_XE [=m]=m


vim +98 fs/exec_test.c

    85	
    86	static void exec_test_bprm_stack_limits(struct kunit *test)
    87	{
    88		/* Double-check the constants. */
    89		KUNIT_EXPECT_EQ(test, _STK_LIM, SZ_8M);
    90		KUNIT_EXPECT_EQ(test, ARG_MAX, 32 * SZ_4K);
    91	
    92		for (int i = 0; i < ARRAY_SIZE(bprm_stack_limits_results); i++) {
    93			const struct bprm_stack_limits_result *result = &bprm_stack_limits_results[i];
    94			struct linux_binprm bprm = result->bprm;
    95			int rc;
    96	
    97			rc = bprm_stack_limits(&bprm);
  > 98			KUNIT_EXPECT_EQ_MSG(test, rc, result->expected_rc, "on loop %d", i);
  > 99			KUNIT_EXPECT_EQ_MSG(test, bprm.argmin, result->expected_argmin, "on loop %d", i);
   100		}
   101	}
   102	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

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