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selftests/vm/pkeys: Add a regression test for setting PKRU through ptrace

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commit 6ea25770b0 upstream

This tests PTRACE_SETREGSET with NT_X86_XSTATE modifying PKRU directly and
removing the PKRU bit from XSTATE_BV.

Signed-off-by: Kyle Huey <me@kylehuey.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20221115230932.7126-7-khuey%40kylehuey.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kyle Huey 2023-01-09 13:02:14 -08:00 • committed by Justin Hammond
parent 921b089af2
commit ae14b7746b
2 changed files with 141 additions and 2 deletions
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12
tools/testing/selftests/vm/pkey-x86.h
View file

@ -119,6 +119,18 @@ static inline int cpu_has_pkeys(void)
return 1;
}
static inline int cpu_max_xsave_size(void)
{
unsigned long XSTATE_CPUID = 0xd;
unsigned int eax;
unsigned int ebx;
unsigned int ecx;
unsigned int edx;
__cpuid_count(XSTATE_CPUID, 0, eax, ebx, ecx, edx);
return ecx;
}
static inline u32 pkey_bit_position(int pkey)
{
return pkey * PKEY_BITS_PER_PKEY;

131
tools/testing/selftests/vm/protection_keys.c
View file

@ -18,12 +18,13 @@
* do a plain mprotect() to a mprotect_pkey() area and make sure the pkey sticks
*
* Compile like this:
* gcc -o protection_keys -O2 -g -std=gnu99 -pthread -Wall protection_keys.c -lrt -ldl -lm
* gcc -m32 -o protection_keys_32 -O2 -g -std=gnu99 -pthread -Wall protection_keys.c -lrt -ldl -lm
* gcc -mxsave -o protection_keys -O2 -g -std=gnu99 -pthread -Wall protection_keys.c -lrt -ldl -lm
* gcc -mxsave -m32 -o protection_keys_32 -O2 -g -std=gnu99 -pthread -Wall protection_keys.c -lrt -ldl -lm
*/
#define _GNU_SOURCE
#define __SANE_USERSPACE_TYPES__
#include <errno.h>
#include <linux/elf.h>
#include <linux/futex.h>
#include <time.h>
#include <sys/time.h>
@ -1550,6 +1551,129 @@ void test_implicit_mprotect_exec_only_memory(int *ptr, u16 pkey)
do_not_expect_pkey_fault("plain read on recently PROT_EXEC area");
}
#if defined(__i386__) || defined(__x86_64__)
void test_ptrace_modifies_pkru(int *ptr, u16 pkey)
{
u32 new_pkru;
pid_t child;
int status, ret;
int pkey_offset = pkey_reg_xstate_offset();
size_t xsave_size = cpu_max_xsave_size();
void *xsave;
u32 *pkey_register;
u64 *xstate_bv;
struct iovec iov;
new_pkru = ~read_pkey_reg();
/* Don't make PROT_EXEC mappings inaccessible */
new_pkru &= ~3;
child = fork();
pkey_assert(child >= 0);
dprintf3("[%d] fork() ret: %d\n", getpid(), child);
if (!child) {
ptrace(PTRACE_TRACEME, 0, 0, 0);
/* Stop and allow the tracer to modify PKRU directly */
raise(SIGSTOP);
/*
* need __read_pkey_reg() version so we do not do shadow_pkey_reg
* checking
*/
if (__read_pkey_reg() != new_pkru)
exit(1);
/* Stop and allow the tracer to clear XSTATE_BV for PKRU */
raise(SIGSTOP);
if (__read_pkey_reg() != 0)
exit(1);
/* Stop and allow the tracer to examine PKRU */
raise(SIGSTOP);
exit(0);
}
pkey_assert(child == waitpid(child, &status, 0));
dprintf3("[%d] waitpid(%d) status: %x\n", getpid(), child, status);
pkey_assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP);
xsave = (void *)malloc(xsave_size);
pkey_assert(xsave > 0);
/* Modify the PKRU register directly */
iov.iov_base = xsave;
iov.iov_len = xsave_size;
ret = ptrace(PTRACE_GETREGSET, child, (void *)NT_X86_XSTATE, &iov);
pkey_assert(ret == 0);
pkey_register = (u32 *)(xsave + pkey_offset);
pkey_assert(*pkey_register == read_pkey_reg());
*pkey_register = new_pkru;
ret = ptrace(PTRACE_SETREGSET, child, (void *)NT_X86_XSTATE, &iov);
pkey_assert(ret == 0);
/* Test that the modification is visible in ptrace before any execution */
memset(xsave, 0xCC, xsave_size);
ret = ptrace(PTRACE_GETREGSET, child, (void *)NT_X86_XSTATE, &iov);
pkey_assert(ret == 0);
pkey_assert(*pkey_register == new_pkru);
/* Execute the tracee */
ret = ptrace(PTRACE_CONT, child, 0, 0);
pkey_assert(ret == 0);
/* Test that the tracee saw the PKRU value change */
pkey_assert(child == waitpid(child, &status, 0));
dprintf3("[%d] waitpid(%d) status: %x\n", getpid(), child, status);
pkey_assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP);
/* Test that the modification is visible in ptrace after execution */
memset(xsave, 0xCC, xsave_size);
ret = ptrace(PTRACE_GETREGSET, child, (void *)NT_X86_XSTATE, &iov);
pkey_assert(ret == 0);
pkey_assert(*pkey_register == new_pkru);
/* Clear the PKRU bit from XSTATE_BV */
xstate_bv = (u64 *)(xsave + 512);
*xstate_bv &= ~(1 << 9);
ret = ptrace(PTRACE_SETREGSET, child, (void *)NT_X86_XSTATE, &iov);
pkey_assert(ret == 0);
/* Test that the modification is visible in ptrace before any execution */
memset(xsave, 0xCC, xsave_size);
ret = ptrace(PTRACE_GETREGSET, child, (void *)NT_X86_XSTATE, &iov);
pkey_assert(ret == 0);
pkey_assert(*pkey_register == 0);
ret = ptrace(PTRACE_CONT, child, 0, 0);
pkey_assert(ret == 0);
/* Test that the tracee saw the PKRU value go to 0 */
pkey_assert(child == waitpid(child, &status, 0));
dprintf3("[%d] waitpid(%d) status: %x\n", getpid(), child, status);
pkey_assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP);
/* Test that the modification is visible in ptrace after execution */
memset(xsave, 0xCC, xsave_size);
ret = ptrace(PTRACE_GETREGSET, child, (void *)NT_X86_XSTATE, &iov);
pkey_assert(ret == 0);
pkey_assert(*pkey_register == 0);
ret = ptrace(PTRACE_CONT, child, 0, 0);
pkey_assert(ret == 0);
pkey_assert(child == waitpid(child, &status, 0));
dprintf3("[%d] waitpid(%d) status: %x\n", getpid(), child, status);
pkey_assert(WIFEXITED(status));
pkey_assert(WEXITSTATUS(status) == 0);
free(xsave);
}
#endif
void test_mprotect_pkey_on_unsupported_cpu(int *ptr, u16 pkey)
{
int size = PAGE_SIZE;
@ -1585,6 +1709,9 @@ void (*pkey_tests[])(int *ptr, u16 pkey) = {
test_pkey_syscalls_bad_args,
test_pkey_alloc_exhaust,
test_pkey_alloc_free_attach_pkey0,
#if defined(__i386__) || defined(__x86_64__)
test_ptrace_modifies_pkru,
#endif
};
void run_tests_once(void)