summaryrefslogtreecommitdiffstats
path: root/drivers
diff options
context:
space:
mode:
Diffstat (limited to 'drivers')
-rw-r--r--drivers/misc/lkdtm/bugs.c66
-rw-r--r--drivers/misc/lkdtm/core.c1
-rw-r--r--drivers/misc/lkdtm/lkdtm.h1
3 files changed, 68 insertions, 0 deletions
diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index 17f839dee976..3741b783fe44 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -266,3 +266,69 @@ void lkdtm_STACK_GUARD_PAGE_TRAILING(void)
pr_err("FAIL: accessed page after stack!\n");
}
+
+void lkdtm_UNSET_SMEP(void)
+{
+#ifdef CONFIG_X86_64
+#define MOV_CR4_DEPTH 64
+ void (*direct_write_cr4)(unsigned long val);
+ unsigned char *insn;
+ unsigned long cr4;
+ int i;
+
+ cr4 = native_read_cr4();
+
+ if ((cr4 & X86_CR4_SMEP) != X86_CR4_SMEP) {
+ pr_err("FAIL: SMEP not in use\n");
+ return;
+ }
+ cr4 &= ~(X86_CR4_SMEP);
+
+ pr_info("trying to clear SMEP normally\n");
+ native_write_cr4(cr4);
+ if (cr4 == native_read_cr4()) {
+ pr_err("FAIL: pinning SMEP failed!\n");
+ cr4 |= X86_CR4_SMEP;
+ pr_info("restoring SMEP\n");
+ native_write_cr4(cr4);
+ return;
+ }
+ pr_info("ok: SMEP did not get cleared\n");
+
+ /*
+ * To test the post-write pinning verification we need to call
+ * directly into the middle of native_write_cr4() where the
+ * cr4 write happens, skipping any pinning. This searches for
+ * the cr4 writing instruction.
+ */
+ insn = (unsigned char *)native_write_cr4;
+ for (i = 0; i < MOV_CR4_DEPTH; i++) {
+ /* mov %rdi, %cr4 */
+ if (insn[i] == 0x0f && insn[i+1] == 0x22 && insn[i+2] == 0xe7)
+ break;
+ /* mov %rdi,%rax; mov %rax, %cr4 */
+ if (insn[i] == 0x48 && insn[i+1] == 0x89 &&
+ insn[i+2] == 0xf8 && insn[i+3] == 0x0f &&
+ insn[i+4] == 0x22 && insn[i+5] == 0xe0)
+ break;
+ }
+ if (i >= MOV_CR4_DEPTH) {
+ pr_info("ok: cannot locate cr4 writing call gadget\n");
+ return;
+ }
+ direct_write_cr4 = (void *)(insn + i);
+
+ pr_info("trying to clear SMEP with call gadget\n");
+ direct_write_cr4(cr4);
+ if (native_read_cr4() & X86_CR4_SMEP) {
+ pr_info("ok: SMEP removal was reverted\n");
+ } else {
+ pr_err("FAIL: cleared SMEP not detected!\n");
+ cr4 |= X86_CR4_SMEP;
+ pr_info("restoring SMEP\n");
+ native_write_cr4(cr4);
+ }
+#else
+ pr_err("FAIL: this test is x86_64-only\n");
+#endif
+}
diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index 8a1428d4f138..a5a04185a3d8 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -114,6 +114,7 @@ static const struct crashtype crashtypes[] = {
CRASHTYPE(CORRUPT_USER_DS),
CRASHTYPE(STACK_GUARD_PAGE_LEADING),
CRASHTYPE(STACK_GUARD_PAGE_TRAILING),
+ CRASHTYPE(UNSET_SMEP),
CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),
CRASHTYPE(OVERWRITE_ALLOCATION),
CRASHTYPE(WRITE_AFTER_FREE),
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index 23dc565b4307..bbcd370786d4 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -26,6 +26,7 @@ void lkdtm_CORRUPT_LIST_DEL(void);
void lkdtm_CORRUPT_USER_DS(void);
void lkdtm_STACK_GUARD_PAGE_LEADING(void);
void lkdtm_STACK_GUARD_PAGE_TRAILING(void);
+void lkdtm_UNSET_SMEP(void);
/* lkdtm_heap.c */
void lkdtm_OVERWRITE_ALLOCATION(void);