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lkdtm/bugs: Adjust recursion test to avoid elision
While I was able to trick gcc into keeping a pathological recursion, Clang was not so easily fooled. Instead, switch to using "volatile" and side-effects to keep the stack variable allocated and to run the function. Additionally renames "OVERFLOW" to "EXHAUST_STACK" to better describe the test. Signed-off-by: Kees Cook <keescook@chromium.org>
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2bf8496f6e
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3 changed files with 21 additions and 10 deletions
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@ -32,12 +32,20 @@ static int recur_count = REC_NUM_DEFAULT;
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static DEFINE_SPINLOCK(lock_me_up);
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static int recursive_loop(int remaining)
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/*
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* Make sure compiler does not optimize this function or stack frame away:
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* - function marked noinline
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* - stack variables are marked volatile
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* - stack variables are written (memset()) and read (pr_info())
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* - function has external effects (pr_info())
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* */
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static int noinline recursive_loop(int remaining)
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{
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char buf[REC_STACK_SIZE];
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volatile char buf[REC_STACK_SIZE];
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/* Make sure compiler does not optimize this away. */
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memset(buf, (remaining & 0xff) | 0x1, REC_STACK_SIZE);
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memset((void *)buf, remaining & 0xFF, sizeof(buf));
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pr_info("loop %d/%d ...\n", (int)buf[remaining % sizeof(buf)],
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recur_count);
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if (!remaining)
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return 0;
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else
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@ -81,9 +89,12 @@ void lkdtm_LOOP(void)
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;
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}
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void lkdtm_OVERFLOW(void)
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void lkdtm_EXHAUST_STACK(void)
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{
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(void) recursive_loop(recur_count);
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pr_info("Calling function with %d frame size to depth %d ...\n",
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REC_STACK_SIZE, recur_count);
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recursive_loop(recur_count);
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pr_info("FAIL: survived without exhausting stack?!\n");
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}
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static noinline void __lkdtm_CORRUPT_STACK(void *stack)
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@ -119,12 +119,12 @@ static const struct crashtype crashtypes[] = {
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CRASHTYPE(WARNING),
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CRASHTYPE(EXCEPTION),
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CRASHTYPE(LOOP),
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CRASHTYPE(OVERFLOW),
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CRASHTYPE(EXHAUST_STACK),
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CRASHTYPE(CORRUPT_STACK),
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CRASHTYPE(CORRUPT_STACK_STRONG),
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CRASHTYPE(CORRUPT_LIST_ADD),
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CRASHTYPE(CORRUPT_LIST_DEL),
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CRASHTYPE(CORRUPT_USER_DS),
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CRASHTYPE(CORRUPT_STACK),
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CRASHTYPE(CORRUPT_STACK_STRONG),
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CRASHTYPE(STACK_GUARD_PAGE_LEADING),
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CRASHTYPE(STACK_GUARD_PAGE_TRAILING),
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CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),
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@ -13,7 +13,7 @@ void lkdtm_BUG(void);
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void lkdtm_WARNING(void);
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void lkdtm_EXCEPTION(void);
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void lkdtm_LOOP(void);
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void lkdtm_OVERFLOW(void);
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void lkdtm_EXHAUST_STACK(void);
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void lkdtm_CORRUPT_STACK(void);
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void lkdtm_CORRUPT_STACK_STRONG(void);
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void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void);
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