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usercopy: Adjust tests to deal with SMAP/PAN 

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 drops the bad copy_from_user() test that would trigger a
memcpy() against userspace on failure.

Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2017-02-13 11:25:26 -08:00
parent 4fbfeb8bd6
commit f5f893c57e
1 changed files with 24 additions and 8 deletions
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32
lib/test_user_copy.c
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@ -58,7 +58,9 @@ static int __init test_user_copy_init(void)
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),
@ -68,31 +70,45 @@ 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, 0, 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(kmem + PAGE_SIZE, 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(kmem + PAGE_SIZE, 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(kmem + PAGE_SIZE, 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");