diff options
Diffstat (limited to '')
| -rw-r--r-- | drivers/misc/lkdtm/heap.c | 221 |
1 files changed, 221 insertions, 0 deletions
diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c new file mode 100644 index 000000000..1323bc16f --- /dev/null +++ b/drivers/misc/lkdtm/heap.c @@ -0,0 +1,221 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * This is for all the tests relating directly to heap memory, including + * page allocation and slab allocations. + */ +#include "lkdtm.h" +#include <linux/slab.h> +#include <linux/sched.h> + +static struct kmem_cache *double_free_cache; +static struct kmem_cache *a_cache; +static struct kmem_cache *b_cache; + +/* + * This tries to stay within the next largest power-of-2 kmalloc cache + * to avoid actually overwriting anything important if it's not detected + * correctly. + */ +void lkdtm_OVERWRITE_ALLOCATION(void) +{ + size_t len = 1020; + u32 *data = kmalloc(len, GFP_KERNEL); + if (!data) + return; + + data[1024 / sizeof(u32)] = 0x12345678; + kfree(data); +} + +void lkdtm_WRITE_AFTER_FREE(void) +{ + int *base, *again; + size_t len = 1024; + /* + * The slub allocator uses the first word to store the free + * pointer in some configurations. Use the middle of the + * allocation to avoid running into the freelist + */ + size_t offset = (len / sizeof(*base)) / 2; + + base = kmalloc(len, GFP_KERNEL); + if (!base) + return; + pr_info("Allocated memory %p-%p\n", base, &base[offset * 2]); + pr_info("Attempting bad write to freed memory at %p\n", + &base[offset]); + kfree(base); + base[offset] = 0x0abcdef0; + /* Attempt to notice the overwrite. */ + again = kmalloc(len, GFP_KERNEL); + kfree(again); + if (again != base) + pr_info("Hmm, didn't get the same memory range.\n"); +} + +void lkdtm_READ_AFTER_FREE(void) +{ + int *base, *val, saw; + size_t len = 1024; + /* + * The slub allocator will use the either the first word or + * the middle of the allocation to store the free pointer, + * depending on configurations. Store in the second word to + * avoid running into the freelist. + */ + size_t offset = sizeof(*base); + + base = kmalloc(len, GFP_KERNEL); + if (!base) { + pr_info("Unable to allocate base memory.\n"); + return; + } + + val = kmalloc(len, GFP_KERNEL); + if (!val) { + pr_info("Unable to allocate val memory.\n"); + kfree(base); + return; + } + + *val = 0x12345678; + base[offset] = *val; + pr_info("Value in memory before free: %x\n", base[offset]); + + kfree(base); + + pr_info("Attempting bad read from freed memory\n"); + saw = base[offset]; + if (saw != *val) { + /* Good! Poisoning happened, so declare a win. */ + pr_info("Memory correctly poisoned (%x)\n", saw); + BUG(); + } + pr_info("Memory was not poisoned\n"); + + kfree(val); +} + +void lkdtm_WRITE_BUDDY_AFTER_FREE(void) +{ + unsigned long p = __get_free_page(GFP_KERNEL); + if (!p) { + pr_info("Unable to allocate free page\n"); + return; + } + + pr_info("Writing to the buddy page before free\n"); + memset((void *)p, 0x3, PAGE_SIZE); + free_page(p); + schedule(); + pr_info("Attempting bad write to the buddy page after free\n"); + memset((void *)p, 0x78, PAGE_SIZE); + /* Attempt to notice the overwrite. */ + p = __get_free_page(GFP_KERNEL); + free_page(p); + schedule(); +} + +void lkdtm_READ_BUDDY_AFTER_FREE(void) +{ + unsigned long p = __get_free_page(GFP_KERNEL); + int saw, *val; + int *base; + + if (!p) { + pr_info("Unable to allocate free page\n"); + return; + } + + val = kmalloc(1024, GFP_KERNEL); + if (!val) { + pr_info("Unable to allocate val memory.\n"); + free_page(p); + return; + } + + base = (int *)p; + + *val = 0x12345678; + base[0] = *val; + pr_info("Value in memory before free: %x\n", base[0]); + free_page(p); + pr_info("Attempting to read from freed memory\n"); + saw = base[0]; + if (saw != *val) { + /* Good! Poisoning happened, so declare a win. */ + pr_info("Memory correctly poisoned (%x)\n", saw); + BUG(); + } + pr_info("Buddy page was not poisoned\n"); + + kfree(val); +} + +void lkdtm_SLAB_FREE_DOUBLE(void) +{ + int *val; + + val = kmem_cache_alloc(double_free_cache, GFP_KERNEL); + if (!val) { + pr_info("Unable to allocate double_free_cache memory.\n"); + return; + } + + /* Just make sure we got real memory. */ + *val = 0x12345678; + pr_info("Attempting double slab free ...\n"); + kmem_cache_free(double_free_cache, val); + kmem_cache_free(double_free_cache, val); +} + +void lkdtm_SLAB_FREE_CROSS(void) +{ + int *val; + + val = kmem_cache_alloc(a_cache, GFP_KERNEL); + if (!val) { + pr_info("Unable to allocate a_cache memory.\n"); + return; + } + + /* Just make sure we got real memory. */ + *val = 0x12345679; + pr_info("Attempting cross-cache slab free ...\n"); + kmem_cache_free(b_cache, val); +} + +void lkdtm_SLAB_FREE_PAGE(void) +{ + unsigned long p = __get_free_page(GFP_KERNEL); + + pr_info("Attempting non-Slab slab free ...\n"); + kmem_cache_free(NULL, (void *)p); + free_page(p); +} + +/* + * We have constructors to keep the caches distinctly separated without + * needing to boot with "slab_nomerge". + */ +static void ctor_double_free(void *region) +{ } +static void ctor_a(void *region) +{ } +static void ctor_b(void *region) +{ } + +void __init lkdtm_heap_init(void) +{ + double_free_cache = kmem_cache_create("lkdtm-heap-double_free", + 64, 0, 0, ctor_double_free); + a_cache = kmem_cache_create("lkdtm-heap-a", 64, 0, 0, ctor_a); + b_cache = kmem_cache_create("lkdtm-heap-b", 64, 0, 0, ctor_b); +} + +void __exit lkdtm_heap_exit(void) +{ + kmem_cache_destroy(double_free_cache); + kmem_cache_destroy(a_cache); + kmem_cache_destroy(b_cache); +} |