[PATCH 7/9] lkdtm: Add CONFIG hints in errors where possible
From: Kees Cook
Date: Wed Jun 23 2021 - 16:40:18 EST
For various failure conditions, try to include some details about where
to look for reasons about the failure.
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
drivers/misc/lkdtm/bugs.c | 8 ++-
drivers/misc/lkdtm/cfi.c | 3 +-
drivers/misc/lkdtm/core.c | 51 +++++++++++++++++++
drivers/misc/lkdtm/fortify.c | 3 +-
drivers/misc/lkdtm/heap.c | 10 ++--
drivers/misc/lkdtm/lkdtm.h | 41 +++++++++++++++
drivers/misc/lkdtm/stackleak.c | 4 +-
drivers/misc/lkdtm/usercopy.c | 7 ++-
.../testing/selftests/lkdtm/stack-entropy.sh | 1 +
9 files changed, 117 insertions(+), 11 deletions(-)
diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index 9ff02bdf3153..7c7335506c45 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -303,8 +303,10 @@ void lkdtm_CORRUPT_LIST_ADD(void)
if (target[0] == NULL && target[1] == NULL)
pr_err("Overwrite did not happen, but no BUG?!\n");
- else
+ else {
pr_err("list_add() corruption not detected!\n");
+ pr_expected_config(CONFIG_DEBUG_LIST);
+ }
}
void lkdtm_CORRUPT_LIST_DEL(void)
@@ -328,8 +330,10 @@ void lkdtm_CORRUPT_LIST_DEL(void)
if (target[0] == NULL && target[1] == NULL)
pr_err("Overwrite did not happen, but no BUG?!\n");
- else
+ else {
pr_err("list_del() corruption not detected!\n");
+ pr_expected_config(CONFIG_DEBUG_LIST);
+ }
}
/* Test that VMAP_STACK is actually allocating with a leading guard page */
diff --git a/drivers/misc/lkdtm/cfi.c b/drivers/misc/lkdtm/cfi.c
index e73ebdbfa806..c9aeddef1044 100644
--- a/drivers/misc/lkdtm/cfi.c
+++ b/drivers/misc/lkdtm/cfi.c
@@ -38,5 +38,6 @@ void lkdtm_CFI_FORWARD_PROTO(void)
func = (void *)lkdtm_increment_int;
func(&called_count);
- pr_info("Fail: survived mismatched prototype function call!\n");
+ pr_err("FAIL: survived mismatched prototype function call!\n");
+ pr_expected_config(CONFIG_CFI_CLANG);
}
diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index 2c89fc18669f..c185ae4719c3 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -26,6 +26,7 @@
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/debugfs.h>
+#include <linux/init.h>
#define DEFAULT_COUNT 10
@@ -398,6 +399,56 @@ static ssize_t direct_entry(struct file *f, const char __user *user_buf,
return count;
}
+#ifndef MODULE
+/*
+ * To avoid needing to export parse_args(), just don't use this code
+ * when LKDTM is built as a module.
+ */
+struct check_cmdline_args {
+ const char *param;
+ int value;
+};
+
+static int lkdtm_parse_one(char *param, char *val,
+ const char *unused, void *arg)
+{
+ struct check_cmdline_args *args = arg;
+
+ /* short circuit if we already found a value. */
+ if (args->value != -ESRCH)
+ return 0;
+ if (strncmp(param, args->param, strlen(args->param)) == 0) {
+ bool bool_result;
+ int ret;
+
+ ret = kstrtobool(val, &bool_result);
+ if (ret == 0)
+ args->value = bool_result;
+ }
+ return 0;
+}
+
+int lkdtm_check_bool_cmdline(const char *param)
+{
+ char *command_line;
+ struct check_cmdline_args args = {
+ .param = param,
+ .value = -ESRCH,
+ };
+
+ command_line = kstrdup(saved_command_line, GFP_KERNEL);
+ if (!command_line)
+ return -ENOMEM;
+
+ parse_args("Setting sysctl args", command_line,
+ NULL, 0, -1, -1, &args, lkdtm_parse_one);
+
+ kfree(command_line);
+
+ return args.value;
+}
+#endif
+
static struct dentry *lkdtm_debugfs_root;
static int __init lkdtm_module_init(void)
diff --git a/drivers/misc/lkdtm/fortify.c b/drivers/misc/lkdtm/fortify.c
index faf29cf04baa..0f51d31b57ca 100644
--- a/drivers/misc/lkdtm/fortify.c
+++ b/drivers/misc/lkdtm/fortify.c
@@ -76,7 +76,8 @@ void lkdtm_FORTIFIED_STRSCPY(void)
*/
strscpy(dst, src, strlen(src));
- pr_warn("FAIL: No overflow in above strscpy()\n");
+ pr_err("FAIL: strscpy() overflow not detected!\n");
+ pr_expected_config(CONFIG_FORTIFY_SOURCE);
kfree(src);
}
diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c
index 36be5e353cd0..a3bb0577ed8b 100644
--- a/drivers/misc/lkdtm/heap.c
+++ b/drivers/misc/lkdtm/heap.c
@@ -109,9 +109,10 @@ void lkdtm_READ_AFTER_FREE(void)
if (saw != *val) {
/* Good! Poisoning happened, so declare a win. */
pr_info("Memory correctly poisoned (%x)\n", saw);
- BUG();
+ } else {
+ pr_err("FAIL: Memory was not poisoned!\n");
+ pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free");
}
- pr_info("Memory was not poisoned\n");
kfree(val);
}
@@ -165,9 +166,10 @@ void lkdtm_READ_BUDDY_AFTER_FREE(void)
if (saw != *val) {
/* Good! Poisoning happened, so declare a win. */
pr_info("Memory correctly poisoned (%x)\n", saw);
- BUG();
+ } else {
+ pr_err("FAIL: Buddy page was not poisoned!\n");
+ pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free");
}
- pr_info("Buddy page was not poisoned\n");
kfree(val);
}
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index c6baf4f1e1db..e491bc571808 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -6,6 +6,47 @@
#include <linux/kernel.h>
+#define pr_expected_config(kconfig) \
+{ \
+ if (IS_ENABLED(kconfig)) \
+ pr_err("Unexpected! This kernel was built with " #kconfig "=y\n"); \
+ else \
+ pr_warn("This is probably expected, since this kernel was built *without* " #kconfig "=y\n"); \
+}
+
+#ifndef MODULE
+int lkdtm_check_bool_cmdline(const char *param);
+#define pr_expected_config_param(kconfig, param) \
+{ \
+ if (IS_ENABLED(kconfig)) { \
+ switch (lkdtm_check_bool_cmdline(param)) { \
+ case 0: \
+ pr_warn("This is probably expected, since this kernel was built with " #kconfig "=y but booted with '" param "=N'\n"); \
+ break; \
+ case 1: \
+ pr_err("Unexpected! This kernel was built with " #kconfig "=y and booted with '" param "=Y'\n"); \
+ break; \
+ default: \
+ pr_err("Unexpected! This kernel was built with " #kconfig "=y (and booted without '" param "' specified)\n"); \
+ } \
+ } else { \
+ switch (lkdtm_check_bool_cmdline(param)) { \
+ case 0: \
+ pr_warn("This is probably expected, as kernel was built *without* " #kconfig "=y and booted with '" param "=N'\n"); \
+ break; \
+ case 1: \
+ pr_err("Unexpected! This kernel was built *without* " #kconfig "=y but booted with '" param "=Y'\n"); \
+ break; \
+ default: \
+ pr_err("This is probably expected, since this kernel was built *without* " #kconfig "=y (and booted without '" param "' specified)\n"); \
+ break; \
+ } \
+ } \
+}
+#else
+#define pr_expected_config_param(kconfig, param) pr_expected_config(kconfig)
+#endif
+
/* bugs.c */
void __init lkdtm_bugs_init(int *recur_param);
void lkdtm_PANIC(void);
diff --git a/drivers/misc/lkdtm/stackleak.c b/drivers/misc/lkdtm/stackleak.c
index d1a5c0705be3..00db21ff115e 100644
--- a/drivers/misc/lkdtm/stackleak.c
+++ b/drivers/misc/lkdtm/stackleak.c
@@ -74,8 +74,8 @@ void lkdtm_STACKLEAK_ERASING(void)
end:
if (test_failed) {
- pr_err("FAIL: the thread stack is NOT properly erased\n");
- dump_stack();
+ pr_err("FAIL: the thread stack is NOT properly erased!\n");
+ pr_expected_config(CONFIG_GCC_PLUGIN_STACKLEAK);
} else {
pr_info("OK: the rest of the thread stack is properly erased\n");
}
diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c
index 15d220ef35a5..9161ce7ed47a 100644
--- a/drivers/misc/lkdtm/usercopy.c
+++ b/drivers/misc/lkdtm/usercopy.c
@@ -173,6 +173,8 @@ static void do_usercopy_heap_size(bool to_user)
goto free_user;
}
}
+ pr_err("FAIL: bad usercopy not detected!\n");
+ pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");
free_user:
vm_munmap(user_addr, PAGE_SIZE);
@@ -248,6 +250,8 @@ static void do_usercopy_heap_whitelist(bool to_user)
goto free_user;
}
}
+ pr_err("FAIL: bad usercopy not detected!\n");
+ pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");
free_user:
vm_munmap(user_alloc, PAGE_SIZE);
@@ -319,7 +323,8 @@ void lkdtm_USERCOPY_KERNEL(void)
pr_warn("copy_to_user failed, but lacked Oops\n");
goto free_user;
}
- pr_err("FAIL: survived bad copy_to_user()\n");
+ pr_err("FAIL: bad copy_to_user() not detected!\n");
+ pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");
free_user:
vm_munmap(user_addr, PAGE_SIZE);
diff --git a/tools/testing/selftests/lkdtm/stack-entropy.sh b/tools/testing/selftests/lkdtm/stack-entropy.sh
index b1b8a5097cbb..1b4d95d575f8 100755
--- a/tools/testing/selftests/lkdtm/stack-entropy.sh
+++ b/tools/testing/selftests/lkdtm/stack-entropy.sh
@@ -30,6 +30,7 @@ rm -f "$log"
# We would expect any functional stack randomization to be at least 5 bits.
if [ "$bits" -lt 5 ]; then
+ echo "Stack entropy is low! Booted without 'randomize_kstack_offset=y'?"
exit 1
else
exit 0
--
2.30.2