Under SMAP/PAN/etc, we cannot write directly to userspace memory, so this rearranges the test bytes to get written through copy_to_user(). Additionally fixes a small memory leak on user memory allocation failure, and drops the bad copy_from_user() test that would trigger a memcpy() against userspace on failure.
Signed-off-by: Kees Cook <[email protected]> --- lib/test_user_copy.c | 45 ++++++++++++++++++++++++++++++++------------- 1 file changed, 32 insertions(+), 13 deletions(-) diff --git a/lib/test_user_copy.c b/lib/test_user_copy.c index 54bd898e356f..ac3a60ba9331 100644 --- a/lib/test_user_copy.c +++ b/lib/test_user_copy.c @@ -49,8 +49,8 @@ static int __init test_user_copy_init(void) zerokmem = kzalloc(PAGE_SIZE * 2, GFP_KERNEL); if (!zerokmem) { - kfree(kmem); - return -ENOMEM; + ret = -ENOMEM; + goto out_kmem; } user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2, @@ -58,14 +58,16 @@ static int __init test_user_copy_init(void) MAP_ANONYMOUS | MAP_PRIVATE, 0); if (user_addr >= (unsigned long)(TASK_SIZE)) { pr_warn("Failed to allocate user memory\n"); - kfree(kmem); - return -ENOMEM; + ret = -ENOMEM; + goto out_zerokmem; } usermem = (char __user *)user_addr; bad_usermem = (char *)user_addr; - /* Legitimate usage: none of these should fail. */ + /* + * Legitimate usage: none of these copies should fail. + */ ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE), "legitimate copy_from_user failed"); ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE), @@ -75,36 +77,53 @@ static int __init test_user_copy_init(void) ret |= test(put_user(value, (unsigned long __user *)usermem), "legitimate put_user failed"); - /* Invalid usage: none of these should succeed. */ + /* + * Invalid usage: none of these copies should succeed. + */ + + /* Prepare kernel memory with check values. */ memset(kmem, 0x5A, PAGE_SIZE); + memset(kmem + PAGE_SIZE, 0x5B, PAGE_SIZE); + + /* Reject kernel-to-kernel copies through copy_from_user(). */ ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE), PAGE_SIZE), "illegal all-kernel copy_from_user passed"); + + /* Destination half of buffer should have been zeroed. */ ret |= test(memcmp(zerokmem, kmem, PAGE_SIZE), "zeroing failure for illegal all-kernel copy_from_user"); - memset(bad_usermem, 0x5A, PAGE_SIZE); + +#if 0 + /* + * When running with SMAP/PAN/etc, this will Oops the kernel + * due to the zeroing of userspace memory on failure. This needs + * to be tested in LKDTM instead, since this test module does not + * expect to explode. + */ ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem, PAGE_SIZE), "illegal reversed copy_from_user passed"); - ret |= test(memcmp(zerokmem, bad_usermem, PAGE_SIZE), - "zeroing failure for illegal reversed copy_from_user"); +#endif ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE, PAGE_SIZE), "illegal all-kernel copy_to_user passed"); ret |= test(!copy_to_user((char __user *)kmem, bad_usermem, PAGE_SIZE), "illegal reversed copy_to_user passed"); - memset(kmem, 0x5A, PAGE_SIZE); + + value = 0x5A; ret |= test(!get_user(value, (unsigned long __user *)kmem), "illegal get_user passed"); - ret |= test(memcmp(zerokmem, kmem, sizeof(value)), - "zeroing failure for illegal get_user"); + ret |= test(value != 0, "zeroing failure for illegal get_user"); ret |= test(!put_user(value, (unsigned long __user *)kmem), "illegal put_user passed"); vm_munmap(user_addr, PAGE_SIZE * 2); - kfree(kmem); +out_zerokmem: kfree(zerokmem); +out_kmem: + kfree(kmem); if (ret == 0) { pr_info("tests passed.\n"); -- 2.7.4 -- Kees Cook Pixel Security
