Commit 8bfdbddd authored by Christophe Leroy's avatar Christophe Leroy Committed by Kees Cook
Browse files

lkdtm/bugs: Don't expect thread termination without CONFIG_UBSAN_TRAP 



When you don't select CONFIG_UBSAN_TRAP, you get:

  # echo ARRAY_BOUNDS > /sys/kernel/debug/provoke-crash/DIRECT
[  102.265827] ================================================================================
[  102.278433] UBSAN: array-index-out-of-bounds in drivers/misc/lkdtm/bugs.c:342:16
[  102.287207] index 8 is out of range for type 'char [8]'
[  102.298722] ================================================================================
[  102.313712] lkdtm: FAIL: survived array bounds overflow!
[  102.318770] lkdtm: Unexpected! This kernel (5.16.0-rc1-s3k-dev-01884-g720dcf79314a ppc) was built with CONFIG_UBSAN_BOUNDS=y

It is not correct because when CONFIG_UBSAN_TRAP is not selected
you can't expect array bounds overflow to kill the thread.

Modify the logic so that when the kernel is built with
CONFIG_UBSAN_BOUNDS but without CONFIG_UBSAN_TRAP, you get a warning
about CONFIG_UBSAN_TRAP not been selected instead.

This also require a fix of pr_expected_config(), otherwise the
following error is encountered.

  CC      drivers/misc/lkdtm/bugs.o
drivers/misc/lkdtm/bugs.c: In function 'lkdtm_ARRAY_BOUNDS':
drivers/misc/lkdtm/bugs.c:351:2: error: 'else' without a previous 'if'
  351 |  else
      |  ^~~~

Fixes: c75be56e ("lkdtm/bugs: Add ARRAY_BOUNDS to selftests")
Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/363b58690e907c677252467a94fe49444c80ea76.1649704381.git.christophe.leroy@csgroup.eu
parent f387e86d

drivers/misc/lkdtm/bugs.c

+4 −1
Original line number Diff line number Diff line
@@ -351,6 +351,9 @@ void lkdtm_ARRAY_BOUNDS(void) 
	kfree(not_checked);

	kfree(checked);

	pr_err("FAIL: survived array bounds overflow!\n");

	if (IS_ENABLED(CONFIG_UBSAN_BOUNDS))

		pr_expected_config(CONFIG_UBSAN_TRAP);

	else

		pr_expected_config(CONFIG_UBSAN_BOUNDS);

}

drivers/misc/lkdtm/lkdtm.h

+4 −4
Original line number Diff line number Diff line
@@ -9,19 +9,19 @@ 
extern char *lkdtm_kernel_info;



#define pr_expected_config(kconfig)				\

{								\

do {								\

	if (IS_ENABLED(kconfig)) 				\

		pr_err("Unexpected! This %s was built with " #kconfig "=y\n", \

			lkdtm_kernel_info);			\

	else							\

		pr_warn("This is probably expected, since this %s was built *without* " #kconfig "=y\n", \

			lkdtm_kernel_info);			\

}

} while (0)



#ifndef MODULE

int lkdtm_check_bool_cmdline(const char *param);

#define pr_expected_config_param(kconfig, param)		\

{								\

do {								\

	if (IS_ENABLED(kconfig)) {				\

		switch (lkdtm_check_bool_cmdline(param)) {	\

		case 0:						\
@@ -52,7 +52,7 @@ int lkdtm_check_bool_cmdline(const char *param); 
			break;					\

		}						\

	}							\

}

} while (0)

#else

#define pr_expected_config_param(kconfig, param) pr_expected_config(kconfig)

#endif