diff options
author | Daniel Axtens <dja@axtens.net> | 2020-12-16 05:43:47 +0100 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-16 07:46:16 +0100 |
commit | d96938daae2a2ae20e5d3d38ddb85d8afdaee628 (patch) | |
tree | f6acad466d3facc3dea1f146af9d86f19cd92f9e | |
parent | lib: string.h: detect intra-object overflow in fortified string functions (diff) | |
download | linux-d96938daae2a2ae20e5d3d38ddb85d8afdaee628.tar.xz linux-d96938daae2a2ae20e5d3d38ddb85d8afdaee628.zip |
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@privacyrequired.com
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Francis Laniel <laniel_francis@privacyrequired.com>
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: 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>
-rw-r--r-- | drivers/misc/lkdtm/bugs.c | 50 | ||||
-rw-r--r-- | drivers/misc/lkdtm/core.c | 2 | ||||
-rw-r--r-- | drivers/misc/lkdtm/lkdtm.h | 2 |
3 files changed, 54 insertions, 0 deletions
diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c index a0675d4154d2..110f5a8538e9 100644 --- a/drivers/misc/lkdtm/bugs.c +++ b/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); +} diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c index 97803f213d9d..b8c51a633fcc 100644 --- a/drivers/misc/lkdtm/core.c +++ b/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), diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h index 6dec4c9b442f..49e6b945feb7 100644 --- a/drivers/misc/lkdtm/lkdtm.h +++ b/drivers/misc/lkdtm/lkdtm.h @@ -32,6 +32,8 @@ void lkdtm_STACK_GUARD_PAGE_TRAILING(void); 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); |