Merge tag 'hardening-v6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull kernel hardening updates from Kees Cook:
 "Most of the collected changes here are fixes across the tree for
  various hardening features (details noted below).

  The most notable new feature here is the addition of the memcpy()
  overflow warning (under CONFIG_FORTIFY_SOURCE), which is the next step
  on the path to killing the common class of "trivially detectable"
  buffer overflow conditions (i.e. on arrays with sizes known at compile
  time) that have resulted in many exploitable vulnerabilities over the
  years (e.g. BleedingTooth).

  This feature is expected to still have some undiscovered false
  positives. It's been in -next for a full development cycle and all the
  reported false positives have been fixed in their respective trees.
  All the known-bad code patterns we could find with Coccinelle are also
  either fixed in their respective trees or in flight.

  The commit message in commit 54d9469bc515 ("fortify: Add run-time WARN
  for cross-field memcpy()") for the feature has extensive details, but
  I'll repeat here that this is a warning _only_, and is not intended to
  actually block overflows (yet). The many patches fixing array sizes
  and struct members have been landing for several years now, and we're
  finally able to turn this on to find any remaining stragglers.

  Summary:

  Various fixes across several hardening areas:

   - loadpin: Fix verity target enforcement (Matthias Kaehlcke).

   - zero-call-used-regs: Add missing clobbers in paravirt (Bill
     Wendling).

   - CFI: clean up sparc function pointer type mismatches (Bart Van
     Assche).

   - Clang: Adjust compiler flag detection for various Clang changes
     (Sami Tolvanen, Kees Cook).

   - fortify: Fix warnings in arch-specific code in sh, ARM, and xen.

  Improvements to existing features:

   - testing: improve overflow KUnit test, introduce fortify KUnit test,
     add more coverage to LKDTM tests (Bart Van Assche, Kees Cook).

   - overflow: Relax overflow type checking for wider utility.

  New features:

   - string: Introduce strtomem() and strtomem_pad() to fill a gap in
     strncpy() replacement needs.

   - um: Enable FORTIFY_SOURCE support.

   - fortify: Enable run-time struct member memcpy() overflow warning"

* tag 'hardening-v6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (27 commits)
  Makefile.extrawarn: Move -Wcast-function-type-strict to W=1
  hardening: Remove Clang's enable flag for -ftrivial-auto-var-init=zero
  sparc: Unbreak the build
  x86/paravirt: add extra clobbers with ZERO_CALL_USED_REGS enabled
  x86/paravirt: clean up typos and grammaros
  fortify: Convert to struct vs member helpers
  fortify: Explicitly check bounds are compile-time constants
  x86/entry: Work around Clang __bdos() bug
  ARM: decompressor: Include .data.rel.ro.local
  fortify: Adjust KUnit test for modular build
  sh: machvec: Use char[] for section boundaries
  kunit/memcpy: Avoid pathological compile-time string size
  lib: Improve the is_signed_type() kunit test
  LoadPin: Require file with verity root digests to have a header
  dm: verity-loadpin: Only trust verity targets with enforcement
  LoadPin: Fix Kconfig doc about format of file with verity digests
  um: Enable FORTIFY_SOURCE
  lkdtm: Update tests for memcpy() run-time warnings
  fortify: Add run-time WARN for cross-field memcpy()
  fortify: Use SIZE_MAX instead of (size_t)-1
  ...

4 files changed, 108 insertions, 13 deletions

diff --git a/drivers/md/dm-verity-loadpin.c b/drivers/md/dm-verity-loadpin.c
index 387ec43aef72..4f78cc55c251 100644
--- a/drivers/md/dm-verity-loadpin.c
+++ b/drivers/md/dm-verity-loadpin.c
@@ -14,6 +14,7 @@ LIST_HEAD(dm_verity_loadpin_trusted_root_digests);
 
 static bool is_trusted_verity_target(struct dm_target *ti)
 {
+	int verity_mode;
 	u8 *root_digest;
 	unsigned int digest_size;
 	struct dm_verity_loadpin_trusted_root_digest *trd;
@@ -22,6 +23,13 @@ static bool is_trusted_verity_target(struct dm_target *ti)
 	if (!dm_is_verity_target(ti))
 		return false;
 
+	verity_mode = dm_verity_get_mode(ti);
+
+	if ((verity_mode != DM_VERITY_MODE_EIO) &&
+	    (verity_mode != DM_VERITY_MODE_RESTART) &&
+	    (verity_mode != DM_VERITY_MODE_PANIC))
+		return false;
+
 	if (dm_verity_get_root_digest(ti, &root_digest, &digest_size))
 		return false;
 
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 94b6cb599db4..8a00cc42e498 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -1447,6 +1447,22 @@ bool dm_is_verity_target(struct dm_target *ti)
 }
 
 /*
+ * Get the verity mode (error behavior) of a verity target.
+ *
+ * Returns the verity mode of the target, or -EINVAL if 'ti' is not a verity
+ * target.
+ */
+int dm_verity_get_mode(struct dm_target *ti)
+{
+	struct dm_verity *v = ti->private;
+
+	if (!dm_is_verity_target(ti))
+		return -EINVAL;
+
+	return v->mode;
+}
+
+/*
  * Get the root digest of a verity target.
  *
  * Returns a copy of the root digest, the caller is responsible for
diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
index 45455de1b4bc..98f306ec6a33 100644
--- a/drivers/md/dm-verity.h
+++ b/drivers/md/dm-verity.h
@@ -134,6 +134,7 @@ extern int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
 				 sector_t block, u8 *digest, bool *is_zero);
 
 extern bool dm_is_verity_target(struct dm_target *ti);
+extern int dm_verity_get_mode(struct dm_target *ti);
 extern int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest,
 				     unsigned int *digest_size);
 
diff --git a/drivers/misc/lkdtm/fortify.c b/drivers/misc/lkdtm/fortify.c
index 080293fa3c52..015927665678 100644
--- a/drivers/misc/lkdtm/fortify.c
+++ b/drivers/misc/lkdtm/fortify.c
@@ -10,28 +10,31 @@
 
 static volatile int fortify_scratch_space;
 
-static void lkdtm_FORTIFIED_OBJECT(void)
+static void lkdtm_FORTIFY_STR_OBJECT(void)
 {
 	struct target {
 		char a[10];
-	} target[2] = {};
+		int foo;
+	} target[3] = {};
 	/*
 	 * Using volatile prevents the compiler from determining the value of
 	 * 'size' at compile time. Without that, we would get a compile error
 	 * rather than a runtime error.
 	 */
-	volatile int size = 11;
+	volatile int size = 20;
+
+	pr_info("trying to strcmp() past the end of a struct\n");
 
-	pr_info("trying to read past the end of a struct\n");
+	strncpy(target[0].a, target[1].a, size);
 
 	/* Store result to global to prevent the code from being eliminated */
-	fortify_scratch_space = memcmp(&target[0], &target[1], size);
+	fortify_scratch_space = target[0].a[3];
 
-	pr_err("FAIL: fortify did not block an object overread!\n");
+	pr_err("FAIL: fortify did not block a strncpy() object write overflow!\n");
 	pr_expected_config(CONFIG_FORTIFY_SOURCE);
 }
 
-static void lkdtm_FORTIFIED_SUBOBJECT(void)
+static void lkdtm_FORTIFY_STR_MEMBER(void)
 {
 	struct target {
 		char a[10];
@@ -44,7 +47,7 @@ static void lkdtm_FORTIFIED_SUBOBJECT(void)
 	strscpy(src, "over ten bytes", size);
 	size = strlen(src) + 1;
 
-	pr_info("trying to strncpy past the end of a member of a struct\n");
+	pr_info("trying to strncpy() past the end of a struct member...\n");
 
 	/*
 	 * strncpy(target.a, src, 20); will hit a compile error because the
@@ -56,7 +59,72 @@ static void lkdtm_FORTIFIED_SUBOBJECT(void)
 	/* Store result to global to prevent the code from being eliminated */
 	fortify_scratch_space = target.a[3];
 
-	pr_err("FAIL: fortify did not block an sub-object overrun!\n");
+	pr_err("FAIL: fortify did not block a strncpy() struct member write overflow!\n");
+	pr_expected_config(CONFIG_FORTIFY_SOURCE);
+
+	kfree(src);
+}
+
+static void lkdtm_FORTIFY_MEM_OBJECT(void)
+{
+	int before[10];
+	struct target {
+		char a[10];
+		int foo;
+	} target = {};
+	int after[10];
+	/*
+	 * Using volatile prevents the compiler from determining the value of
+	 * 'size' at compile time. Without that, we would get a compile error
+	 * rather than a runtime error.
+	 */
+	volatile int size = 20;
+
+	memset(before, 0, sizeof(before));
+	memset(after, 0, sizeof(after));
+	fortify_scratch_space = before[5];
+	fortify_scratch_space = after[5];
+
+	pr_info("trying to memcpy() past the end of a struct\n");
+
+	pr_info("0: %zu\n", __builtin_object_size(&target, 0));
+	pr_info("1: %zu\n", __builtin_object_size(&target, 1));
+	pr_info("s: %d\n", size);
+	memcpy(&target, &before, size);
+
+	/* Store result to global to prevent the code from being eliminated */
+	fortify_scratch_space = target.a[3];
+
+	pr_err("FAIL: fortify did not block a memcpy() object write overflow!\n");
+	pr_expected_config(CONFIG_FORTIFY_SOURCE);
+}
+
+static void lkdtm_FORTIFY_MEM_MEMBER(void)
+{
+	struct target {
+		char a[10];
+		char b[10];
+	} target;
+	volatile int size = 20;
+	char *src;
+
+	src = kmalloc(size, GFP_KERNEL);
+	strscpy(src, "over ten bytes", size);
+	size = strlen(src) + 1;
+
+	pr_info("trying to memcpy() past the end of a struct member...\n");
+
+	/*
+	 * strncpy(target.a, src, 20); will hit a compile error because the
+	 * compiler knows at build time that target.a < 20 bytes. Use a
+	 * volatile to force a runtime error.
+	 */
+	memcpy(target.a, src, size);
+
+	/* Store result to global to prevent the code from being eliminated */
+	fortify_scratch_space = target.a[3];
+
+	pr_err("FAIL: fortify did not block a memcpy() struct member write overflow!\n");
 	pr_expected_config(CONFIG_FORTIFY_SOURCE);
 
 	kfree(src);
@@ -67,7 +135,7 @@ static void lkdtm_FORTIFIED_SUBOBJECT(void)
  * strscpy and generate a panic because there is a write overflow (i.e. src
  * length is greater than dst length).
  */
-static void lkdtm_FORTIFIED_STRSCPY(void)
+static void lkdtm_FORTIFY_STRSCPY(void)
 {
 	char *src;
 	char dst[5];
@@ -136,9 +204,11 @@ static void lkdtm_FORTIFIED_STRSCPY(void)
 }
 
 static struct crashtype crashtypes[] = {
-	CRASHTYPE(FORTIFIED_OBJECT),
-	CRASHTYPE(FORTIFIED_SUBOBJECT),
-	CRASHTYPE(FORTIFIED_STRSCPY),
+	CRASHTYPE(FORTIFY_STR_OBJECT),
+	CRASHTYPE(FORTIFY_STR_MEMBER),
+	CRASHTYPE(FORTIFY_MEM_OBJECT),
+	CRASHTYPE(FORTIFY_MEM_MEMBER),
+	CRASHTYPE(FORTIFY_STRSCPY),
 };
 
 struct crashtype_category fortify_crashtypes = {