lkdtm: improve use-after-free tests
This improves the order of operations on the use-after-free tests to try to make sure we've executed any available sanity-checking code, and to report the poisoning that was found. Signed-off-by: Kees Cook <keescook@chromium.org>
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@ -417,7 +417,7 @@ static void lkdtm_do_action(enum ctype which)
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break;
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}
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case CT_WRITE_AFTER_FREE: {
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int *base;
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int *base, *again;
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size_t len = 1024;
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/*
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* The slub allocator uses the first word to store the free
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@ -428,10 +428,16 @@ static void lkdtm_do_action(enum ctype which)
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base = kmalloc(len, GFP_KERNEL);
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pr_info("Allocated memory %p-%p\n", base, &base[offset * 2]);
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kfree(base);
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pr_info("Attempting bad write to freed memory at %p\n",
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&base[offset]);
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kfree(base);
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base[offset] = 0x0abcdef0;
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/* Attempt to notice the overwrite. */
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again = kmalloc(len, GFP_KERNEL);
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kfree(again);
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if (again != base)
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pr_info("Hmm, didn't get the same memory range.\n");
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break;
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}
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case CT_READ_AFTER_FREE: {
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@ -462,7 +468,7 @@ static void lkdtm_do_action(enum ctype which)
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saw = base[offset];
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if (saw != *val) {
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/* Good! Poisoning happened, so declare a win. */
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pr_info("Memory correctly poisoned, calling BUG\n");
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pr_info("Memory correctly poisoned (%x)\n", saw);
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BUG();
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}
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pr_info("Memory was not poisoned\n");
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@ -480,6 +486,11 @@ static void lkdtm_do_action(enum ctype which)
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schedule();
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pr_info("Attempting bad write to the buddy page after free\n");
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memset((void *)p, 0x78, PAGE_SIZE);
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/* Attempt to notice the overwrite. */
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p = __get_free_page(GFP_KERNEL);
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free_page(p);
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schedule();
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break;
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}
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case CT_READ_BUDDY_AFTER_FREE: {
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@ -503,7 +514,7 @@ static void lkdtm_do_action(enum ctype which)
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saw = base[0];
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if (saw != *val) {
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/* Good! Poisoning happened, so declare a win. */
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pr_info("Buddy page correctly poisoned, calling BUG\n");
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pr_info("Memory correctly poisoned (%x)\n", saw);
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BUG();
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}
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pr_info("Buddy page was not poisoned\n");
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