The patch titled
Subject: lkdtm: tests for FORTIFY_SOURCE
has been added to the -mm tree. Its filename is
lkdtm-tests-for-fortify_source.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/lkdtm-tests-for-fortify_source.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/lkdtm-tests-for-fortify_source.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Daniel Axtens <dja@xxxxxxxxxx>
Subject: lkdtm: tests for FORTIFY_SOURCE
Add code to test both:
- runtime detection of the overrun of a structure. This covers the
__builtin_object_size(x, 0) case. This test is called FORTIFY_OBJECT.
- runtime detection of the overrun of a char array within a structure.
This covers the __builtin_object_size(x, 1) case which can be used
for some string functions. This test is called FORTIFY_SUBOBJECT.
Link: https://lkml.kernel.org/r/20201122162451.27551-3-laniel_francis@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Daniel Axtens <dja@xxxxxxxxxx>
Signed-off-by: Francis Laniel <laniel_francis@xxxxxxxxxxxxxxxxxxx>
Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Daniel Micay <danielmicay@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/misc/lkdtm/bugs.c | 50 +++++++++++++++++++++++++++++++++++
drivers/misc/lkdtm/core.c | 2 +
drivers/misc/lkdtm/lkdtm.h | 2 +
3 files changed, 54 insertions(+)
--- a/drivers/misc/lkdtm/bugs.c~lkdtm-tests-for-fortify_source
+++ a/drivers/misc/lkdtm/bugs.c
@@ -482,3 +482,53 @@ noinline void lkdtm_CORRUPT_PAC(void)
pr_err("XFAIL: this test is arm64-only\n");
#endif
}
+
+void lkdtm_FORTIFY_OBJECT(void)
+{
+ struct target {
+ char a[10];
+ } target[2] = {};
+ int result;
+
+ /*
+ * Using volatile prevents the compiler from determining the value of
+ * 'size' at compile time. Without that, we would get a compile error
+ * rather than a runtime error.
+ */
+ volatile int size = 11;
+
+ pr_info("trying to read past the end of a struct\n");
+
+ result = memcmp(&target[0], &target[1], size);
+
+ /* Print result to prevent the code from being eliminated */
+ pr_err("FAIL: fortify did not catch an object overread!\n"
+ "\"%d\" was the memcmp result.\n", result);
+}
+
+void lkdtm_FORTIFY_SUBOBJECT(void)
+{
+ struct target {
+ char a[10];
+ char b[10];
+ } target;
+ char *src;
+
+ src = kmalloc(20, GFP_KERNEL);
+ strscpy(src, "over ten bytes", 20);
+
+ pr_info("trying to strcpy past the end of a member of a struct\n");
+
+ /*
+ * strncpy(target.a, src, 20); will hit a compile error because the
+ * compiler knows at build time that target.a < 20 bytes. Use strcpy()
+ * to force a runtime error.
+ */
+ strcpy(target.a, src);
+
+ /* Use target.a to prevent the code from being eliminated */
+ pr_err("FAIL: fortify did not catch an sub-object overrun!\n"
+ "\"%s\" was copied.\n", target.a);
+
+ kfree(src);
+}
--- a/drivers/misc/lkdtm/core.c~lkdtm-tests-for-fortify_source
+++ a/drivers/misc/lkdtm/core.c
@@ -117,6 +117,8 @@ static const struct crashtype crashtypes
CRASHTYPE(UNSET_SMEP),
CRASHTYPE(CORRUPT_PAC),
CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),
+ CRASHTYPE(FORTIFY_OBJECT),
+ CRASHTYPE(FORTIFY_SUBOBJECT),
CRASHTYPE(OVERWRITE_ALLOCATION),
CRASHTYPE(WRITE_AFTER_FREE),
CRASHTYPE(READ_AFTER_FREE),
--- a/drivers/misc/lkdtm/lkdtm.h~lkdtm-tests-for-fortify_source
+++ a/drivers/misc/lkdtm/lkdtm.h
@@ -32,6 +32,8 @@ void lkdtm_STACK_GUARD_PAGE_TRAILING(voi
void lkdtm_UNSET_SMEP(void);
void lkdtm_DOUBLE_FAULT(void);
void lkdtm_CORRUPT_PAC(void);
+void lkdtm_FORTIFY_OBJECT(void);
+void lkdtm_FORTIFY_SUBOBJECT(void);
/* lkdtm_heap.c */
void __init lkdtm_heap_init(void);
_
Patches currently in -mm which might be from dja@xxxxxxxxxx are
stringh-detect-intra-object-overflow-in-fortified-string-functions.patch
lkdtm-tests-for-fortify_source.patch
