On Wed, Jun 12, 2024 at 09:21:52PM +0200, Geert Uytterhoeven wrote: > Hi Kees, > > On Wed, Jun 12, 2024 at 6:51 PM Kees Cook <[email protected]> wrote: > > On Wed, Jun 12, 2024 at 05:13:39PM +0800, David Gow wrote: > > > On Tue, 11 Jun 2024 at 05:33, Kees Cook <[email protected]> wrote: > > > > Convert the runtime tests of hardened usercopy to standard KUnit tests. > > > > > > > > Co-developed-by: Vitor Massaru Iha <[email protected]> > > > > Signed-off-by: Vitor Massaru Iha <[email protected]> > > > > Link: https://lore.kernel.org/r/[email protected] > > > > Tested-by: Ivan Orlov <[email protected]> > > > > Signed-off-by: Kees Cook <[email protected]> > > > > --- > > > > > > This looks good, particularly with the x86 fix applied. > > > > > > It's still hanging on m68k -- I think at the 'illegal reversed > > > copy_to_user passed' test -- but I'll admit to not having tried to > > > debug it further. > > > > > > One other (set of) notes below about using KUNIT_EXPECT_MEMEQ_MSG(), > > > otherwise (assuming the m68k stuff isn't actually a regression, which > > > I haven't tested but I imagine is unlikely), > > > > I'm trying to debug a hang on m68k in the usercopy behavioral testing > > routines. It's testing for the pathological case of having inverted > > arguments to copy_to_user(): > > > > user_addr = kunit_vm_mmap(test, NULL, 0, priv->size, > > PROT_READ | PROT_WRITE | PROT_EXEC, > > MAP_ANONYMOUS | MAP_PRIVATE, 0); > > ... > > bad_usermem = (char *)user_addr; > > ... > > KUNIT_EXPECT_NE_MSG(test, copy_to_user((char __user *)kmem, > > bad_usermem, > > PAGE_SIZE), 0, > > "illegal reversed copy_to_user passed"); > > > > On other architectures, this immediate fails because the access_ok() > > check rejects it. On m68k with CONFIG_ALTERNATE_USER_ADDRESS_SPACE, > > access_ok() short-circuits to "true". I've tried reading > > arch/m68k/include/asm/uaccess.h but I'm not sure what's happening under > > CONFIG_CPU_HAS_ADDRESS_SPACES. > > On m68k CPUs that support CPU_HAS_ADDRESS_SPACES (i.e. all traditional > 680x0 that can run real Linux), the CPU has separate address spaces > for kernel and user addresses. Accessing userspace addresses is done > using the special "moves" instruction, so we can just use the MMU to > catch invalid accesses.
Okay, that's what I suspected. I think I'll need to just not test this particular case for archs with separate address spaces, since it would be meaningless. > > > For now I've excluded that test for m68k, but I'm not sure what's > > expected to happen here on m68k for this set of bad arguments. Can you > > advise? > > Perhaps the kernel address is actually a valid user address, or > vice versa? Right -- I think that's what's happened. > > Does the test work on systems that use 4G/4G for kernel/userspace > instead of the usual 1G/3G split? > > /me runs the old test_user_copy.ko on ARAnyM > Seems to take a while? Or it hangs, too? Sounds like the same behavior. > Related reading material > https://lore.kernel.org/all/camuhmduzhwm5_tl7tnaof+uqhejnkgsqf+_vzqgrzb_3euf...@mail.gmail.com/ > https://lore.kernel.org/all/camuhmdvq93ihgcxubjpttahdpjxxlyvasar-m3twbjv0krs...@mail.gmail.com/ Thanks! -Kees -- Kees Cook
