On Tue, Oct 29, 2024 at 03:14:20PM +0100, Maciej Wieczor-Retman wrote: > Recent change in how get_user() handles pointers [1] has a specific case > for LAM. It assigns a different bitmask that's later used to check > whether a pointer comes from userland in get_user(). > > While currently commented out (until LASS [2] is merged into the kernel) > it's worth making changes to the LAM selftest ahead of time. > > Add test case to LAM that utilizes a ioctl (FIOASYNC) syscall which uses > get_user() in its implementation. Execute the syscall with differently > tagged pointers to verify that valid user pointers are passing through > and invalid kernel/non-canonical pointers are not. > > Code was tested on a Sierra Forest Xeon machine that's LAM capable. The > test was ran without issues with both the LAM lines from [1] untouched > and commented out. The test was also ran without issues with LAM_SUP > both enabled and disabled. > > [1] https://lore.kernel.org/all/20241024013214.129639-1-torvalds@xxxxxxxxxxxxxxxxxxxx/ > [2] https://lore.kernel.org/all/20240710160655.3402786-1-alexander.shishkin@xxxxxxxxxxxxxxx/ > > Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx> > --- > tools/testing/selftests/x86/lam.c | 85 +++++++++++++++++++++++++++++++ > 1 file changed, 85 insertions(+) > > diff --git a/tools/testing/selftests/x86/lam.c b/tools/testing/selftests/x86/lam.c > index 0ea4f6813930..3c53d4b7aa61 100644 > --- a/tools/testing/selftests/x86/lam.c > +++ b/tools/testing/selftests/x86/lam.c > @@ -4,6 +4,7 @@ > #include <stdlib.h> > #include <string.h> > #include <sys/syscall.h> > +#include <sys/ioctl.h> > #include <time.h> > #include <signal.h> > #include <setjmp.h> > @@ -43,10 +44,19 @@ > #define FUNC_INHERITE 0x20 > #define FUNC_PASID 0x40 > > +/* get_user() pointer test cases */ > +#define GET_USER_USER 0 > +#define GET_USER_KERNEL_TOP 1 > +#define GET_USER_KERNEL_BOT 2 > +#define GET_USER_KERNEL 3 > + > #define TEST_MASK 0x7f > +#define L5_SIGN_EXT_MASK (0xFFUL << 56) > +#define L4_SIGN_EXT_MASK (0x1FFFFUL << 47) > > #define LOW_ADDR (0x1UL << 30) > #define HIGH_ADDR (0x3UL << 48) > +#define L5_ADDR (0x1UL << 48) > > #define MALLOC_LEN 32 > > @@ -370,6 +380,54 @@ static int handle_syscall(struct testcases *test) > return ret; > } > > +static int get_user_syscall(struct testcases *test) > +{ > + int ret = 0; > + int ptr_value = 0; > + void *ptr = &ptr_value; > + int fd; > + > + uint64_t bitmask = ((uint64_t)ptr & L5_ADDR) ? L5_SIGN_EXT_MASK : > + L4_SIGN_EXT_MASK; Emm. Do you expect stack to be above at the very top of address space on 5-level paging machines? It is not true. We don't allocate any memory above 46-bit unless asked explicitly. See tools/testing/selftests/mm/va_high_addr_switch.c -- Kiryl Shutsemau / Kirill A. Shutemov
