powerpc: make feature-fixup tests fortify-safe

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>

diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c
index f3917705c686cb3d9af359dd741a0ab0e40a615f..41cf5ae273cf74a2747d13b9da2274b8eb2054cb 100644 (file)
--- 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);
        }
 }