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@linux-foundatio... [2] https://lore.kernel.org/all/20240710160655.3402786-1-alexander.shishkin@linu...
Signed-off-by: Maciej Wieczor-Retman maciej.wieczor-retman@intel.com
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