Re: [PATCH v1 2/2] apparmor: test: make static symbols visible during kunit testing

On Tue, Nov 22, 2022 at 2:20 PM John Johansen john.johansen@canonical.com wrote:

On 11/2/22 10:59, Rae Moar wrote:

...

Use macros, VISIBLE_IF_KUNIT and EXPORT_SYMBOL_IF_KUNIT, to allow static symbols to be conditionally set to be visible during KUnit testing. Remove the need to include testing file in the implementation file. Provide example of how static symbols can be dealt with in testing.

Signed-off-by: Rae Moar rmoar@google.com

security/apparmor/Kconfig | 4 +- security/apparmor/Makefile | 2 + security/apparmor/include/policy_unpack.h | 50 ++++++++++++++++ security/apparmor/policy_unpack.c | 72 +++++++---------------- security/apparmor/policy_unpack_test.c | 5 ++ 5 files changed, 80 insertions(+), 53 deletions(-)

diff --git a/security/apparmor/Kconfig b/security/apparmor/Kconfig index cb3496e00d8a..f334e7cccf2d 100644 --- a/security/apparmor/Kconfig +++ b/security/apparmor/Kconfig @@ -106,8 +106,8 @@ config SECURITY_APPARMOR_PARANOID_LOAD Disabling the check will speed up policy loads.

config SECURITY_APPARMOR_KUNIT_TEST

• bool "Build KUnit tests for policy_unpack.c" if !KUNIT_ALL_TESTS
  

• depends on KUNIT=y && SECURITY_APPARMOR
  

• tristate "Build KUnit tests for policy_unpack.c" if !KUNIT_ALL_TESTS
  

• depends on KUNIT && SECURITY_APPARMOR
  default KUNIT_ALL_TESTS
  help
    This builds the AppArmor KUnit tests.
  

diff --git a/security/apparmor/Makefile b/security/apparmor/Makefile index ff23fcfefe19..6a92428375eb 100644 --- a/security/apparmor/Makefile +++ b/security/apparmor/Makefile @@ -8,6 +8,8 @@ apparmor-y := apparmorfs.o audit.o capability.o task.o ipc.o lib.o match.o \ resource.o secid.o file.o policy_ns.o label.o mount.o net.o apparmor-$(CONFIG_SECURITY_APPARMOR_HASH) += crypto.o

+obj-$(CONFIG_SECURITY_APPARMOR_KUNIT_TEST) += policy_unpack_test.o

• clean-files := capability_names.h rlim_names.h net_names.h

  # Build a lower case string table of address family names

diff --git a/security/apparmor/include/policy_unpack.h b/security/apparmor/include/policy_unpack.h index eb5f7d7f132b..a963687bcc9b 100644 --- a/security/apparmor/include/policy_unpack.h +++ b/security/apparmor/include/policy_unpack.h @@ -48,6 +48,43 @@ enum { AAFS_LOADDATA_NDENTS /* count of entries */ };

+/*

• • The AppArmor interface treats data as a type byte followed by the
• • actual data. The interface has the notion of a named entry
• • which has a name (AA_NAME typecode followed by name string) followed by
• • the entries typecode and data. Named types allow for optional
• • elements and extensions to be added and tested for without breaking
• • backwards compatibility.
• */

+enum aa_code {

• AA_U8,
  

• AA_U16,
  

• AA_U32,
  

• AA_U64,
  

• AA_NAME,                /* same as string except it is items name */
  

• AA_STRING,
  

• AA_BLOB,
  

• AA_STRUCT,
  

• AA_STRUCTEND,
  

• AA_LIST,
  

• AA_LISTEND,
  

• AA_ARRAY,
  

• AA_ARRAYEND,
  

+};

+/*

• • aa_ext is the read of the buffer containing the serialized profile. The
• • data is copied into a kernel buffer in apparmorfs and then handed off to
• • the unpack routines.
• */

+struct aa_ext {

• void *start;
  

• void *end;
  

• void *pos;              /* pointer to current position in the buffer */
  

• u32 version;
  

+};

hrmmm, I prefer these symbols to be only available to the unpack code but can live with them being more widely available.

...

/*

• struct aa_loaddata - buffer of policy raw_data set

@@ -126,4 +163,17 @@ static inline void aa_put_loaddata(struct aa_loaddata *data) kref_put(&data->count, aa_loaddata_kref); }

+#if IS_ENABLED(CONFIG_KUNIT) +bool inbounds(struct aa_ext *e, size_t size); +size_t unpack_u16_chunk(struct aa_ext *e, char **chunk); +bool unpack_X(struct aa_ext *e, enum aa_code code); +bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name); +bool unpack_u32(struct aa_ext *e, u32 *data, const char *name); +bool unpack_u64(struct aa_ext *e, u64 *data, const char *name); +size_t unpack_array(struct aa_ext *e, const char *name); +size_t unpack_blob(struct aa_ext *e, char **blob, const char *name); +int unpack_str(struct aa_ext *e, const char **string, const char *name); +int unpack_strdup(struct aa_ext *e, char **string, const char *name);

So this is a problem. If this symbols are going to be visible outside of the unpack code they need to be prefixed with aa_ to help avoid collisions with other kernel code.

Hmm... I agree we need some sort of way of restricting access to these symbols.

As-is, they're _exported_ to a different symbol namespace, so it shouldn't be a problem during linking when built as a module, nor if KUnit is disabled (due to the preprocessor step).

One option is to put these in a separate header (that only the test and policy-unpack code include), but even that doesn't solve the linking problem when built-in.

So I guess namespacing is the only option which solves all of these problems. (It'd be nice if the symbol namespacing system worked for built-ins as well as modules...)

...

+#endif

• #endif /* __POLICY_INTERFACE_H */

diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c index 55d31bac4f35..c23aa70349aa 100644 --- a/security/apparmor/policy_unpack.c +++ b/security/apparmor/policy_unpack.c @@ -14,6 +14,7 @@ */

#include <asm/unaligned.h> +#include <kunit/visibility.h> #include <linux/ctype.h> #include <linux/errno.h> #include <linux/zlib.h> @@ -37,43 +38,6 @@ #define v7 7 #define v8 8 /* full network masking */

-/*

• • The AppArmor interface treats data as a type byte followed by the
• • actual data. The interface has the notion of a named entry
• • which has a name (AA_NAME typecode followed by name string) followed by
• • the entries typecode and data. Named types allow for optional
• • elements and extensions to be added and tested for without breaking
• • backwards compatibility.
• */

-enum aa_code {

• AA_U8,
  

• AA_U16,
  

• AA_U32,
  

• AA_U64,
  

• AA_NAME,                /* same as string except it is items name */
  

• AA_STRING,
  

• AA_BLOB,
  

• AA_STRUCT,
  

• AA_STRUCTEND,
  

• AA_LIST,
  

• AA_LISTEND,
  

• AA_ARRAY,
  

• AA_ARRAYEND,
  

-};

-/*

• • aa_ext is the read of the buffer containing the serialized profile. The
• • data is copied into a kernel buffer in apparmorfs and then handed off to
• • the unpack routines.
• */

-struct aa_ext {

• void *start;
  

• void *end;
  

• void *pos;              /* pointer to current position in the buffer */
  

• u32 version;
  

-};

• /* audit callback for unpack fields */ static void audit_cb(struct audit_buffer *ab, void *va) {

@@ -199,10 +163,11 @@ struct aa_loaddata *aa_loaddata_alloc(size_t size) }

/* test if read will be in packed data bounds */ -static bool inbounds(struct aa_ext *e, size_t size) +VISIBLE_IF_KUNIT bool inbounds(struct aa_ext *e, size_t size) { return (size <= e->end - e->pos); } +EXPORT_SYMBOL_IF_KUNIT(inbounds);

static void *kvmemdup(const void *src, size_t len) { @@ -220,7 +185,7 @@ static void *kvmemdup(const void *src, size_t len)

• Returns: the size of chunk found with the read head at the end of the chunk.

*/ -static size_t unpack_u16_chunk(struct aa_ext *e, char **chunk) +VISIBLE_IF_KUNIT size_t unpack_u16_chunk(struct aa_ext *e, char **chunk) { size_t size = 0; void *pos = e->pos; @@ -239,9 +204,10 @@ static size_t unpack_u16_chunk(struct aa_ext *e, char **chunk) e->pos = pos; return 0; } +EXPORT_SYMBOL_IF_KUNIT(unpack_u16_chunk);

/* unpack control byte */ -static bool unpack_X(struct aa_ext *e, enum aa_code code) +VISIBLE_IF_KUNIT bool unpack_X(struct aa_ext *e, enum aa_code code) { if (!inbounds(e, 1)) return false; @@ -250,6 +216,7 @@ static bool unpack_X(struct aa_ext *e, enum aa_code code) e->pos++; return true; } +EXPORT_SYMBOL_IF_KUNIT(unpack_X);

/**

• unpack_nameX - check is the next element is of type X with a name of @name

@@ -267,7 +234,7 @@ static bool unpack_X(struct aa_ext *e, enum aa_code code)

• Returns: false if either match fails, the read head does not move

*/ -static bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name) +VISIBLE_IF_KUNIT bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name) { /* * May need to reset pos if name or type doesn't match @@ -296,6 +263,7 @@ static bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name) e->pos = pos; return false; } +EXPORT_SYMBOL_IF_KUNIT(unpack_nameX);

static bool unpack_u8(struct aa_ext *e, u8 *data, const char *name) { @@ -315,7 +283,7 @@ static bool unpack_u8(struct aa_ext *e, u8 *data, const char *name) return false; }

-static bool unpack_u32(struct aa_ext *e, u32 *data, const char *name) +VISIBLE_IF_KUNIT bool unpack_u32(struct aa_ext *e, u32 *data, const char *name) { void *pos = e->pos;

@@ -332,8 +300,9 @@ static bool unpack_u32(struct aa_ext *e, u32 *data, const char *name) e->pos = pos; return false; } +EXPORT_SYMBOL_IF_KUNIT(unpack_u32);

-static bool unpack_u64(struct aa_ext *e, u64 *data, const char *name) +VISIBLE_IF_KUNIT bool unpack_u64(struct aa_ext *e, u64 *data, const char *name) { void *pos = e->pos;

@@ -350,8 +319,9 @@ static bool unpack_u64(struct aa_ext *e, u64 *data, const char *name) e->pos = pos; return false; } +EXPORT_SYMBOL_IF_KUNIT(unpack_u64);

-static size_t unpack_array(struct aa_ext *e, const char *name) +VISIBLE_IF_KUNIT size_t unpack_array(struct aa_ext *e, const char *name) { void *pos = e->pos;

@@ -368,8 +338,9 @@ static size_t unpack_array(struct aa_ext *e, const char *name) e->pos = pos; return 0; } +EXPORT_SYMBOL_IF_KUNIT(unpack_array);

-static size_t unpack_blob(struct aa_ext *e, char **blob, const char *name) +VISIBLE_IF_KUNIT size_t unpack_blob(struct aa_ext *e, char **blob, const char *name) { void *pos = e->pos;

@@ -390,8 +361,9 @@ static size_t unpack_blob(struct aa_ext *e, char **blob, const char *name) e->pos = pos; return 0; } +EXPORT_SYMBOL_IF_KUNIT(unpack_blob);

-static int unpack_str(struct aa_ext *e, const char **string, const char *name) +VISIBLE_IF_KUNIT int unpack_str(struct aa_ext *e, const char **string, const char *name) { char *src_str; size_t size = 0; @@ -413,8 +385,9 @@ static int unpack_str(struct aa_ext *e, const char **string, const char *name) e->pos = pos; return 0; } +EXPORT_SYMBOL_IF_KUNIT(unpack_str);

-static int unpack_strdup(struct aa_ext *e, char **string, const char *name) +VISIBLE_IF_KUNIT int unpack_strdup(struct aa_ext *e, char **string, const char *name) { const char *tmp; void *pos = e->pos; @@ -432,6 +405,7 @@ static int unpack_strdup(struct aa_ext *e, char **string, const char *name)

  return res;

} +EXPORT_SYMBOL_IF_KUNIT(unpack_strdup);

Again if the symbols are going to be exported they need the aa_ prefix

But I am not sure this is worth doing, exporting a lot of symbols just so the test code can be built as a module doesn't seem worth it to me.

Again, agreed that we need to namespace these for the non-module case (the symbol namespacing should be okay otherwise).

One of the reasons behind doing this is that there are a few KUnit users who can only run tests which are built as modules. In particular, Android and (IIRC) Red Hat are both configuring all of their kernels with KUnit built as a module, and distributing the KUnit and KUnit test modules in a different package.

If we kept things the way there are, then it'd not be possible to unconditionally _build_ the apparmor tests, but only load and run them on demand (due to the way they're built into the apparmor module, they'd always run when it loads). This is a no-go for Android/Red Hat, so they won't ship or run the apparmor tests. (There are some other tests with the same problem, notably amdgpu, but apparmor seemed a nice first trial-user, as it were, having a small but non-trivial number of symbols to export.)

Thoughts?

...

/** @@ -1251,7 +1225,3 @@ int aa_unpack(struct aa_loaddata *udata, struct list_head *lh,

  return error;

}

-#ifdef CONFIG_SECURITY_APPARMOR_KUNIT_TEST -#include "policy_unpack_test.c" -#endif /* CONFIG_SECURITY_APPARMOR_KUNIT_TEST */ diff --git a/security/apparmor/policy_unpack_test.c b/security/apparmor/policy_unpack_test.c index 0a969b2e03db..3474fe2cd922 100644 --- a/security/apparmor/policy_unpack_test.c +++ b/security/apparmor/policy_unpack_test.c @@ -4,6 +4,7 @@ */

#include <kunit/test.h> +#include <kunit/visibility.h>

#include "include/policy.h" #include "include/policy_unpack.h" @@ -43,6 +44,8 @@ #define TEST_ARRAY_BUF_OFFSET \ (TEST_NAMED_ARRAY_BUF_OFFSET + 3 + strlen(TEST_ARRAY_NAME) + 1)

+MODULE_IMPORT_NS(EXPORTED_FOR_KUNIT_TESTING);

• struct policy_unpack_fixture { struct aa_ext *e; size_t e_size;

@@ -605,3 +608,5 @@ static struct kunit_suite apparmor_policy_unpack_test_module = { };

kunit_test_suite(apparmor_policy_unpack_test_module);

+MODULE_LICENSE("GPL");