On 2024-10-30 at 14:31:51 +0200, Kirill A. Shutemov wrote: >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. Right, I'm not sure why I thought that would work here. >See tools/testing/selftests/mm/va_high_addr_switch.c Thanks for the tip, I'll use mmap/munmap to determine the enabled pagetable level. > >-- > Kiryl Shutsemau / Kirill A. Shutemov -- Kind regards Maciej Wieczór-Retman
