From: Kees Cook <keescook@chromium.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Kees Cook <keescook@chromium.org>,
Guenter Roeck <linux@roeck-us.net>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: [PATCH] lib: stackinit: Adjust target string to 8 bytes for m68k
Date: Tue, 27 Feb 2024 14:46:56 -0800 [thread overview]
Message-ID: <20240227224653.work.603-kees@kernel.org> (raw)
For reasons I cannot understand, m68k moves the start of the stack frame
for consecutive calls to the same function if the function's test
variable is larger than 8 bytes. This was only happening for the char
array test (obviously), so adjust the length of the string for m68k
only. I want the array size to be longer than "unsigned long" for every
given architecture, so the other remain unchanged.
Additionally adjust the error message to be a bit more clear about
what's happened, and move the KUNIT check outside of the consecutive
calls to minimize what happens between them.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Closes: https://lore.kernel.org/lkml/a0d10d50-2720-4ecd-a2c6-c2c5e5aeee65@roeck-us.net/
Signed-off-by: Kees Cook <keescook@chromium.org>
---
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
---
lib/stackinit_kunit.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/lib/stackinit_kunit.c b/lib/stackinit_kunit.c
index 05947a2feb93..dc3c68f46f0a 100644
--- a/lib/stackinit_kunit.c
+++ b/lib/stackinit_kunit.c
@@ -63,7 +63,16 @@ static bool stackinit_range_contains(char *haystack_start, size_t haystack_size,
#define FETCH_ARG_STRING(var) var
#define FETCH_ARG_STRUCT(var) &var
+/*
+ * On m68k, if the leaf function test variable is longer than 8 bytes,
+ * the start of the stack frame moves. 8 is sufficiently large to
+ * test m68k char arrays, but leave it at 16 for other architectures.
+ */
+#ifdef CONFIG_M68K
+#define FILL_SIZE_STRING 8
+#else
#define FILL_SIZE_STRING 16
+#endif
#define INIT_CLONE_SCALAR /**/
#define INIT_CLONE_STRING [FILL_SIZE_STRING]
@@ -165,19 +174,23 @@ static noinline void test_ ## name (struct kunit *test) \
/* Verify all bytes overwritten with 0xFF. */ \
for (sum = 0, i = 0; i < target_size; i++) \
sum += (check_buf[i] != 0xFF); \
- KUNIT_ASSERT_EQ_MSG(test, sum, 0, \
- "leaf fill was not 0xFF!?\n"); \
/* Clear entire check buffer for later bit tests. */ \
memset(check_buf, 0x00, sizeof(check_buf)); \
/* Extract stack-defined variable contents. */ \
ignored = leaf_ ##name((unsigned long)&ignored, 0, \
FETCH_ARG_ ## which(zero)); \
+ /* \
+ * Delay the sum test to here to do as little as \
+ * possible between the two leaf function calls. \
+ */ \
+ KUNIT_ASSERT_EQ_MSG(test, sum, 0, \
+ "leaf fill was not 0xFF!?\n"); \
\
/* Validate that compiler lined up fill and target. */ \
KUNIT_ASSERT_TRUE_MSG(test, \
stackinit_range_contains(fill_start, fill_size, \
target_start, target_size), \
- "stack fill missed target!? " \
+ "stackframe was not the same between calls!? " \
"(fill %zu wide, target offset by %d)\n", \
fill_size, \
(int)((ssize_t)(uintptr_t)fill_start - \
--
2.34.1
next reply other threads:[~2024-02-27 22:46 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-27 22:46 Kees Cook [this message]
2024-02-27 22:56 ` [PATCH] lib: stackinit: Adjust target string to 8 bytes for m68k Andreas Schwab
2024-02-27 23:03 ` Guenter Roeck
2024-02-28 7:58 ` Geert Uytterhoeven
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