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 Suggested-by: Michael Ellerman <m...@ellerman.id.au> Cc: Kees Cook <keesc...@chromium.org> Cc: Daniel Micay <danielmi...@gmail.com> Signed-off-by: Daniel Axtens <d...@axtens.net> --- arch/powerpc/lib/feature-fixups.c | 180 +++++++++++++++++++------------------- 1 file changed, 90 insertions(+), 90 deletions(-) diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c index f3917705c686..41cf5ae273cf 100644 --- a/arch/powerpc/lib/feature-fixups.c +++ b/arch/powerpc/lib/feature-fixups.c @@ -233,192 +233,192 @@ static long calc_offset(struct fixup_entry *entry, unsigned int *p) static 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); } } -- 2.11.0
