@@ -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>
@@ -43,7 +44,15 @@
#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)
@@ -370,6 +379,59 @@ static int handle_syscall(struct testcases *test)
return ret;
}
+static int get_user_syscall(struct testcases *test)
+{
+ int ptr_value = 0;
+ int ret = 0;
+ int fd;
+ void *p, *ptr = &ptr_value;
+
+ p = mmap((void *)HIGH_ADDR, 1, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
+
+ uint64_t bitmask = (p == MAP_FAILED) ? L4_SIGN_EXT_MASK :
+ L5_SIGN_EXT_MASK;
+
+ munmap(p, 1);
+
+ if (test->lam != 0)
+ if (set_lam(test->lam) != 0)
+ return 2;
+
+ fd = memfd_create("lam_ioctl", 0);
+ if (fd == -1)
+ exit(EXIT_FAILURE);
+
+ switch (test->later) {
+ case GET_USER_USER:
+ /* Control group - properly tagger user pointer */
+ ptr = (void *)set_metadata((uint64_t)ptr, test->lam);
+ break;
+ case GET_USER_KERNEL_TOP:
+ /* Kernel address with top bit cleared */
+ bitmask &= (bitmask >> 1);
+ ptr = (void *)((uint64_t)ptr | bitmask);
+ break;
+ case GET_USER_KERNEL_BOT:
+ /* Kernel address with bottom sign-extension bit cleared */
+ bitmask &= (bitmask << 1);
+ ptr = (void *)((uint64_t)ptr | bitmask);
+ break;
+ case GET_USER_KERNEL:
+ /* Try to pass a kernel address */
+ ptr = (void *)((uint64_t)ptr | bitmask);
+ break;
+ default:
+ printf("Invalid test case value passed!\n");
+ break;
+ }
+
+ if (ioctl(fd, FIOASYNC, ptr) != 0)
+ ret = 1;
+
+ return ret;
+}
+
int sys_uring_setup(unsigned int entries, struct io_uring_params *p)
{
return (int)syscall(__NR_io_uring_setup, entries, p);
@@ -883,6 +945,33 @@ static struct testcases syscall_cases[] = {
.test_func = handle_syscall,
.msg = "SYSCALL:[Negative] Disable LAM. Dereferencing pointer with metadata.\n",
},
+ {
+ .later = GET_USER_USER,
+ .lam = LAM_U57_BITS,
+ .test_func = get_user_syscall,
+ .msg = "GET_USER: get_user() and pass a properly tagged user pointer.\n",
+ },
+ {
+ .later = GET_USER_KERNEL_TOP,
+ .expected = 1,
+ .lam = LAM_U57_BITS,
+ .test_func = get_user_syscall,
+ .msg = "GET_USER:[Negative] get_user() with a kernel pointer and the top bit cleared.\n",
+ },
+ {
+ .later = GET_USER_KERNEL_BOT,
+ .expected = 1,
+ .lam = LAM_U57_BITS,
+ .test_func = get_user_syscall,
+ .msg = "GET_USER:[Negative] get_user() with a kernel pointer and the bottom sign-extension bit cleared.\n",
+ },
+ {
+ .later = GET_USER_KERNEL,
+ .expected = 1,
+ .lam = LAM_U57_BITS,
+ .test_func = get_user_syscall,
+ .msg = "GET_USER:[Negative] get_user() and pass a kernel pointer.\n",
+ },
};
static struct testcases mmap_cases[] = {
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. 4/5 level pagetables code paths were also successfully tested in Simics on a 5-level capable machine. [1] https://lore.kernel.org/all/20241024013214.129639-1-torvalds@linux-foundation.org/ [2] https://lore.kernel.org/all/20240710160655.3402786-1-alexander.shishkin@linux.intel.com/ Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com> --- Changelog v2: - Use mmap with HIGH_ADDR to check if we're in 5 or 4 level pagetables. tools/testing/selftests/x86/lam.c | 89 +++++++++++++++++++++++++++++++ 1 file changed, 89 insertions(+)