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selftests/lam: Test get_user() LAM pointer handling

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Recent change in how get_user() handles pointers:

  https://lore.kernel.org/all/20241024013214.129639-1-torvalds@linux-foundation.org/

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().

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.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/1624d9d1b9502517053a056652d50dc5d26884ac.1737990375.git.maciej.wieczor-retman@intel.com
This commit is contained in:
Maciej Wieczor-Retman 2025-01-27 16:31:57 +01:00 committed by Ingo Molnar
parent 51f909dcd1
commit 782b819827
1 changed files with 108 additions and 0 deletions
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108
tools/testing/selftests/x86/lam.c
View File

@ -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)
@ -389,6 +398,78 @@ static int handle_syscall(struct testcases *test)
return ret;
}
static int get_user_syscall(struct testcases *test)
{
uint64_t ptr_address, bitmask;
int fd, ret = 0;
void *ptr;
if (la57_enabled()) {
bitmask = L5_SIGN_EXT_MASK;
ptr_address = HIGH_ADDR;
} else {
bitmask = L4_SIGN_EXT_MASK;
ptr_address = LOW_ADDR;
}
ptr = mmap((void *)ptr_address, PAGE_SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
if (ptr == MAP_FAILED) {
perror("failed to map byte to pass into get_user");
return 1;
}
if (set_lam(test->lam) != 0) {
ret = 2;
goto error;
}
fd = memfd_create("lam_ioctl", 0);
if (fd == -1) {
munmap(ptr, PAGE_SIZE);
exit(EXIT_FAILURE);
}
switch (test->later) {
case GET_USER_USER:
/* Control group - properly tagged 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;
}
/*
* Use FIOASYNC ioctl because it utilizes get_user() internally and is
* very non-invasive to the system. Pass differently tagged pointers to
* get_user() in order to verify that valid user pointers are going
* through and invalid kernel/non-canonical pointers are not.
*/
if (ioctl(fd, FIOASYNC, ptr) != 0)
ret = 1;
close(fd);
error:
munmap(ptr, PAGE_SIZE);
return ret;
}
int sys_uring_setup(unsigned int entries, struct io_uring_params *p)
{
return (int)syscall(__NR_io_uring_setup, entries, p);
@ -902,6 +983,33 @@ 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[] = {