[PATCH 3.16 041/366] powerpc: make feature-fixup tests fortify-safe

Ben Hutchings
2018-11-11T20:05:23Z

From: Daniel Axtens <dja@axtens.net>

commit c69a48cdb301a18697bc8c9935baf4f32861cf9e upstream.

Testing the fortified string functions[1] would cause a kernel panic on
boot in test_feature_fixups() due to a buffer overflow in memcmp.

This boils down to things like this:

extern unsigned int ftr_fixup_test1;
extern unsigned int ftr_fixup_test1_orig;

check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_orig, size) == 0);

We know that these are asm labels so it is safe to read up to 'size'
bytes at those addresses.

However, because we have passed the address of a single unsigned int to
memcmp, the compiler believes the underlying object is in fact a single
unsigned int. So if size > sizeof(unsigned int), there will be a panic
at runtime.

We can fix this by changing the types: instead of calling the asm labels
unsigned ints, call them unsigned int[]s. Therefore the size isn't
incorrectly determined at compile time and we get a regular unsafe
memcmp and no panic.

[1] http://openwall.com/lists/kernel-hardening/2017/05/09/2

Link: http://lkml.kernel.org/r/1497903987-21002-7-git-send-email-keescook@chromium.org
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Kees Cook <keescook@chromium.org>
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Tested-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Daniel Micay <danielmicay@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/powerpc/lib/feature-fixups.c | 180 +++++++++++++++---------------
1 file changed, 90 insertions(+), 90 deletions(-)

--- a/arch/powerpc/lib/feature-fixups.c
+++ b/arch/powerpc/lib/feature-fixups.c
@@ -166,192 +166,192 @@ static long calc_offset(struct fixup_ent

void test_basic_patching(void)
{
- extern unsigned int ftr_fixup_test1;
- extern unsigned int end_ftr_fixup_test1;
- extern unsigned int ftr_fixup_test1_orig;
- extern unsigned int ftr_fixup_test1_expected;
- int size = &end_ftr_fixup_test1 - &ftr_fixup_test1;
+ extern unsigned int ftr_fixup_test1[];
+ extern unsigned int end_ftr_fixup_test1[];
+ extern unsigned int ftr_fixup_test1_orig[];
+ extern unsigned int ftr_fixup_test1_expected[];
+ int size = end_ftr_fixup_test1 - ftr_fixup_test1;

fixup.value = fixup.mask = 8;
- fixup.start_off = calc_offset(&fixup, &ftr_fixup_test1 + 1);
- fixup.end_off = calc_offset(&fixup, &ftr_fixup_test1 + 2);
+ fixup.start_off = calc_offset(&fixup, ftr_fixup_test1 + 1);
+ fixup.end_off = calc_offset(&fixup, ftr_fixup_test1 + 2);
fixup.alt_start_off = fixup.alt_end_off = 0;

/* Sanity check */
- check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_orig, size) == 0);
+ check(memcmp(ftr_fixup_test1, ftr_fixup_test1_orig, size) == 0);

/* Check we don't patch if the value matches */
patch_feature_section(8, &fixup);
- check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_orig, size) == 0);
+ check(memcmp(ftr_fixup_test1, ftr_fixup_test1_orig, size) == 0);

/* Check we do patch if the value doesn't match */
patch_feature_section(0, &fixup);
- check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_expected, size) == 0);
+ check(memcmp(ftr_fixup_test1, ftr_fixup_test1_expected, size) == 0);

/* Check we do patch if the mask doesn't match */
- memcpy(&ftr_fixup_test1, &ftr_fixup_test1_orig, size);
- check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_orig, size) == 0);
+ memcpy(ftr_fixup_test1, ftr_fixup_test1_orig, size);
+ check(memcmp(ftr_fixup_test1, ftr_fixup_test1_orig, size) == 0);
patch_feature_section(~8, &fixup);
- check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_expected, size) == 0);
+ check(memcmp(ftr_fixup_test1, ftr_fixup_test1_expected, size) == 0);
}

static void test_alternative_patching(void)
{
- extern unsigned int ftr_fixup_test2;
- extern unsigned int end_ftr_fixup_test2;
- extern unsigned int ftr_fixup_test2_orig;
- extern unsigned int ftr_fixup_test2_alt;
- extern unsigned int ftr_fixup_test2_expected;
- int size = &end_ftr_fixup_test2 - &ftr_fixup_test2;
+ extern unsigned int ftr_fixup_test2[];
+ extern unsigned int end_ftr_fixup_test2[];
+ extern unsigned int ftr_fixup_test2_orig[];
+ extern unsigned int ftr_fixup_test2_alt[];
+ extern unsigned int ftr_fixup_test2_expected[];
+ int size = end_ftr_fixup_test2 - ftr_fixup_test2;

fixup.value = fixup.mask = 0xF;
- fixup.start_off = calc_offset(&fixup, &ftr_fixup_test2 + 1);
- fixup.end_off = calc_offset(&fixup, &ftr_fixup_test2 + 2);
- fixup.alt_start_off = calc_offset(&fixup, &ftr_fixup_test2_alt);
- fixup.alt_end_off = calc_offset(&fixup, &ftr_fixup_test2_alt + 1);
+ fixup.start_off = calc_offset(&fixup, ftr_fixup_test2 + 1);
+ fixup.end_off = calc_offset(&fixup, ftr_fixup_test2 + 2);
+ fixup.alt_start_off = calc_offset(&fixup, ftr_fixup_test2_alt);
+ fixup.alt_end_off = calc_offset(&fixup, ftr_fixup_test2_alt + 1);

/* Sanity check */
- check(memcmp(&ftr_fixup_test2, &ftr_fixup_test2_orig, size) == 0);
+ check(memcmp(ftr_fixup_test2, ftr_fixup_test2_orig, size) == 0);

/* Check we don't patch if the value matches */
patch_feature_section(0xF, &fixup);
- check(memcmp(&ftr_fixup_test2, &ftr_fixup_test2_orig, size) == 0);
+ check(memcmp(ftr_fixup_test2, ftr_fixup_test2_orig, size) == 0);

/* Check we do patch if the value doesn't match */
patch_feature_section(0, &fixup);
- check(memcmp(&ftr_fixup_test2, &ftr_fixup_test2_expected, size) == 0);
+ check(memcmp(ftr_fixup_test2, ftr_fixup_test2_expected, size) == 0);

/* Check we do patch if the mask doesn't match */
- memcpy(&ftr_fixup_test2, &ftr_fixup_test2_orig, size);
- check(memcmp(&ftr_fixup_test2, &ftr_fixup_test2_orig, size) == 0);
+ memcpy(ftr_fixup_test2, ftr_fixup_test2_orig, size);
+ check(memcmp(ftr_fixup_test2, ftr_fixup_test2_orig, size) == 0);
patch_feature_section(~0xF, &fixup);
- check(memcmp(&ftr_fixup_test2, &ftr_fixup_test2_expected, size) == 0);
+ check(memcmp(ftr_fixup_test2, ftr_fixup_test2_expected, size) == 0);
}

static void test_alternative_case_too_big(void)
{
- extern unsigned int ftr_fixup_test3;
- extern unsigned int end_ftr_fixup_test3;
- extern unsigned int ftr_fixup_test3_orig;
- extern unsigned int ftr_fixup_test3_alt;
- int size = &end_ftr_fixup_test3 - &ftr_fixup_test3;
+ extern unsigned int ftr_fixup_test3[];
+ extern unsigned int end_ftr_fixup_test3[];
+ extern unsigned int ftr_fixup_test3_orig[];
+ extern unsigned int ftr_fixup_test3_alt[];
+ int size = end_ftr_fixup_test3 - ftr_fixup_test3;

fixup.value = fixup.mask = 0xC;
- fixup.start_off = calc_offset(&fixup, &ftr_fixup_test3 + 1);
- fixup.end_off = calc_offset(&fixup, &ftr_fixup_test3 + 2);
- fixup.alt_start_off = calc_offset(&fixup, &ftr_fixup_test3_alt);
- fixup.alt_end_off = calc_offset(&fixup, &ftr_fixup_test3_alt + 2);
+ fixup.start_off = calc_offset(&fixup, ftr_fixup_test3 + 1);
+ fixup.end_off = calc_offset(&fixup, ftr_fixup_test3 + 2);
+ fixup.alt_start_off = calc_offset(&fixup, ftr_fixup_test3_alt);
+ fixup.alt_end_off = calc_offset(&fixup, ftr_fixup_test3_alt + 2);

/* Sanity check */
- check(memcmp(&ftr_fixup_test3, &ftr_fixup_test3_orig, size) == 0);
+ check(memcmp(ftr_fixup_test3, ftr_fixup_test3_orig, size) == 0);

/* Expect nothing to be patched, and the error returned to us */
check(patch_feature_section(0xF, &fixup) == 1);
- check(memcmp(&ftr_fixup_test3, &ftr_fixup_test3_orig, size) == 0);
+ check(memcmp(ftr_fixup_test3, ftr_fixup_test3_orig, size) == 0);
check(patch_feature_section(0, &fixup) == 1);
- check(memcmp(&ftr_fixup_test3, &ftr_fixup_test3_orig, size) == 0);
+ check(memcmp(ftr_fixup_test3, ftr_fixup_test3_orig, size) == 0);
check(patch_feature_section(~0xF, &fixup) == 1);
- check(memcmp(&ftr_fixup_test3, &ftr_fixup_test3_orig, size) == 0);
+ check(memcmp(ftr_fixup_test3, ftr_fixup_test3_orig, size) == 0);
}

static void test_alternative_case_too_small(void)
{
- extern unsigned int ftr_fixup_test4;
- extern unsigned int end_ftr_fixup_test4;
- extern unsigned int ftr_fixup_test4_orig;
- extern unsigned int ftr_fixup_test4_alt;
- extern unsigned int ftr_fixup_test4_expected;
- int size = &end_ftr_fixup_test4 - &ftr_fixup_test4;
+ extern unsigned int ftr_fixup_test4[];
+ extern unsigned int end_ftr_fixup_test4[];
+ extern unsigned int ftr_fixup_test4_orig[];
+ extern unsigned int ftr_fixup_test4_alt[];
+ extern unsigned int ftr_fixup_test4_expected[];
+ int size = end_ftr_fixup_test4 - ftr_fixup_test4;
unsigned long flag;

/* Check a high-bit flag */
flag = 1UL << ((sizeof(unsigned long) - 1) * 8);
fixup.value = fixup.mask = flag;
- fixup.start_off = calc_offset(&fixup, &ftr_fixup_test4 + 1);
- fixup.end_off = calc_offset(&fixup, &ftr_fixup_test4 + 5);
- fixup.alt_start_off = calc_offset(&fixup, &ftr_fixup_test4_alt);
- fixup.alt_end_off = calc_offset(&fixup, &ftr_fixup_test4_alt + 2);
+ fixup.start_off = calc_offset(&fixup, ftr_fixup_test4 + 1);
+ fixup.end_off = calc_offset(&fixup, ftr_fixup_test4 + 5);
+ fixup.alt_start_off = calc_offset(&fixup, ftr_fixup_test4_alt);
+ fixup.alt_end_off = calc_offset(&fixup, ftr_fixup_test4_alt + 2);

/* Sanity check */
- check(memcmp(&ftr_fixup_test4, &ftr_fixup_test4_orig, size) == 0);
+ check(memcmp(ftr_fixup_test4, ftr_fixup_test4_orig, size) == 0);

/* Check we don't patch if the value matches */
patch_feature_section(flag, &fixup);
- check(memcmp(&ftr_fixup_test4, &ftr_fixup_test4_orig, size) == 0);
+ check(memcmp(ftr_fixup_test4, ftr_fixup_test4_orig, size) == 0);

/* Check we do patch if the value doesn't match */
patch_feature_section(0, &fixup);
- check(memcmp(&ftr_fixup_test4, &ftr_fixup_test4_expected, size) == 0);
+ check(memcmp(ftr_fixup_test4, ftr_fixup_test4_expected, size) == 0);

/* Check we do patch if the mask doesn't match */
- memcpy(&ftr_fixup_test4, &ftr_fixup_test4_orig, size);
- check(memcmp(&ftr_fixup_test4, &ftr_fixup_test4_orig, size) == 0);
+ memcpy(ftr_fixup_test4, ftr_fixup_test4_orig, size);
+ check(memcmp(ftr_fixup_test4, ftr_fixup_test4_orig, size) == 0);
patch_feature_section(~flag, &fixup);
- check(memcmp(&ftr_fixup_test4, &ftr_fixup_test4_expected, size) == 0);
+ check(memcmp(ftr_fixup_test4, ftr_fixup_test4_expected, size) == 0);
}

static void test_alternative_case_with_branch(void)
{
- extern unsigned int ftr_fixup_test5;
- extern unsigned int end_ftr_fixup_test5;
- extern unsigned int ftr_fixup_test5_expected;
- int size = &end_ftr_fixup_test5 - &ftr_fixup_test5;
+ extern unsigned int ftr_fixup_test5[];
+ extern unsigned int end_ftr_fixup_test5[];
+ extern unsigned int ftr_fixup_test5_expected[];
+ int size = end_ftr_fixup_test5 - ftr_fixup_test5;

- check(memcmp(&ftr_fixup_test5, &ftr_fixup_test5_expected, size) == 0);
+ check(memcmp(ftr_fixup_test5, ftr_fixup_test5_expected, size) == 0);
}

static void test_alternative_case_with_external_branch(void)
{
- extern unsigned int ftr_fixup_test6;
- extern unsigned int end_ftr_fixup_test6;
- extern unsigned int ftr_fixup_test6_expected;
- int size = &end_ftr_fixup_test6 - &ftr_fixup_test6;
+ extern unsigned int ftr_fixup_test6[];
+ extern unsigned int end_ftr_fixup_test6[];
+ extern unsigned int ftr_fixup_test6_expected[];
+ int size = end_ftr_fixup_test6 - ftr_fixup_test6;

- check(memcmp(&ftr_fixup_test6, &ftr_fixup_test6_expected, size) == 0);
+ check(memcmp(ftr_fixup_test6, ftr_fixup_test6_expected, size) == 0);
}

static void test_cpu_macros(void)
{
- extern u8 ftr_fixup_test_FTR_macros;
- extern u8 ftr_fixup_test_FTR_macros_expected;
- unsigned long size = &ftr_fixup_test_FTR_macros_expected -
- &ftr_fixup_test_FTR_macros;
+ extern u8 ftr_fixup_test_FTR_macros[];
+ extern u8 ftr_fixup_test_FTR_macros_expected[];
+ unsigned long size = ftr_fixup_test_FTR_macros_expected -
+ ftr_fixup_test_FTR_macros;

/* The fixups have already been done for us during boot */
- check(memcmp(&ftr_fixup_test_FTR_macros,
- &ftr_fixup_test_FTR_macros_expected, size) == 0);
+ check(memcmp(ftr_fixup_test_FTR_macros,
+ ftr_fixup_test_FTR_macros_expected, size) == 0);
}

static void test_fw_macros(void)
{
#ifdef CONFIG_PPC64
- extern u8 ftr_fixup_test_FW_FTR_macros;
- extern u8 ftr_fixup_test_FW_FTR_macros_expected;
- unsigned long size = &ftr_fixup_test_FW_FTR_macros_expected -
- &ftr_fixup_test_FW_FTR_macros;
+ extern u8 ftr_fixup_test_FW_FTR_macros[];
+ extern u8 ftr_fixup_test_FW_FTR_macros_expected[];
+ unsigned long size = ftr_fixup_test_FW_FTR_macros_expected -
+ ftr_fixup_test_FW_FTR_macros;

/* The fixups have already been done for us during boot */
- check(memcmp(&ftr_fixup_test_FW_FTR_macros,
- &ftr_fixup_test_FW_FTR_macros_expected, size) == 0);
+ check(memcmp(ftr_fixup_test_FW_FTR_macros,
+ ftr_fixup_test_FW_FTR_macros_expected, size) == 0);
#endif
}

static void test_lwsync_macros(void)
{
- extern u8 lwsync_fixup_test;
- extern u8 end_lwsync_fixup_test;
- extern u8 lwsync_fixup_test_expected_LWSYNC;
- extern u8 lwsync_fixup_test_expected_SYNC;
- unsigned long size = &end_lwsync_fixup_test -
- &lwsync_fixup_test;
+ extern u8 lwsync_fixup_test[];
+ extern u8 end_lwsync_fixup_test[];
+ extern u8 lwsync_fixup_test_expected_LWSYNC[];
+ extern u8 lwsync_fixup_test_expected_SYNC[];
+ unsigned long size = end_lwsync_fixup_test -
+ lwsync_fixup_test;

/* The fixups have already been done for us during boot */
if (cur_cpu_spec->cpu_features & CPU_FTR_LWSYNC) {
- check(memcmp(&lwsync_fixup_test,
- &lwsync_fixup_test_expected_LWSYNC, size) == 0);
+ check(memcmp(lwsync_fixup_test,
+ lwsync_fixup_test_expected_LWSYNC, size) == 0);
} else {
- check(memcmp(&lwsync_fixup_test,
- &lwsync_fixup_test_expected_SYNC, size) == 0);
+ check(memcmp(lwsync_fixup_test,
+ lwsync_fixup_test_expected_SYNC, size) == 0);
}
}