From: Kees Cook <keescook@xxxxxxxxxxxx>
Commit f5f893c57e37ca730808cb2eee3820abd05e7507 upstream.
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.
[arnd: the test module was added in 3.14, and this backported patch
should apply cleanly on all version from 3.14 to 4.10.
The original patch was in 4.11 on top of a context change
I saw the bug triggered with kselftest on a 4.4.y stable kernel]
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
v2: remove a line that accidentally ended up from upstream version
but is not part of the fix.
---
lib/test_user_copy.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/lib/test_user_copy.c b/lib/test_user_copy.c
index 0ecef3e4690e..5e6db6b1e3bd 100644
--- a/lib/test_user_copy.c
+++ b/lib/test_user_copy.c
@@ -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),
@@ -68,19 +70,33 @@ 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.
+ */
+
+ /* 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");
+
+#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");
+#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");
+
ret |= test(!get_user(value, (unsigned long __user *)kmem),
"illegal get_user passed");
ret |= test(!put_user(value, (unsigned long __user *)kmem),
--
2.9.0