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
  ...

3 files changed, 31 insertions, 6 deletions

diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index bd2aabb2c60f..995bc42003e6 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -22,11 +22,17 @@ menu "Memory initialization"
 config CC_HAS_AUTO_VAR_INIT_PATTERN
 	def_bool $(cc-option,-ftrivial-auto-var-init=pattern)
 
-config CC_HAS_AUTO_VAR_INIT_ZERO
-	# GCC ignores the -enable flag, so we can test for the feature with
-	# a single invocation using the flag, but drop it as appropriate in
-	# the Makefile, depending on the presence of Clang.
+config CC_HAS_AUTO_VAR_INIT_ZERO_BARE
+	def_bool $(cc-option,-ftrivial-auto-var-init=zero)
+
+config CC_HAS_AUTO_VAR_INIT_ZERO_ENABLER
+	# Clang 16 and later warn about using the -enable flag, but it
+	# is required before then.
 	def_bool $(cc-option,-ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang)
+	depends on !CC_HAS_AUTO_VAR_INIT_ZERO_BARE
+
+config CC_HAS_AUTO_VAR_INIT_ZERO
+	def_bool CC_HAS_AUTO_VAR_INIT_ZERO_BARE || CC_HAS_AUTO_VAR_INIT_ZERO_ENABLER
 
 choice
 	prompt "Initialize kernel stack variables at function entry"
diff --git a/security/loadpin/Kconfig b/security/loadpin/Kconfig
index 70e7985b2561..6724eaba3d36 100644
--- a/security/loadpin/Kconfig
+++ b/security/loadpin/Kconfig
@@ -33,4 +33,9 @@ config SECURITY_LOADPIN_VERITY
 	  on the LoadPin securityfs entry 'dm-verity'. The ioctl
 	  expects a file descriptor of a file with verity digests as
 	  parameter. The file must be located on the pinned root and
-	  contain a comma separated list of digests.
+	  start with the line:
+
+	  # LOADPIN_TRUSTED_VERITY_ROOT_DIGESTS
+
+	  This is followed by the verity digests, with one digest per
+	  line.
diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
index 44521582dcba..de41621f4998 100644
--- a/security/loadpin/loadpin.c
+++ b/security/loadpin/loadpin.c
@@ -21,6 +21,8 @@
 #include <linux/dm-verity-loadpin.h>
 #include <uapi/linux/loadpin.h>
 
+#define VERITY_DIGEST_FILE_HEADER "# LOADPIN_TRUSTED_VERITY_ROOT_DIGESTS"
+
 static void report_load(const char *origin, struct file *file, char *operation)
 {
 	char *cmdline, *pathname;
@@ -292,9 +294,21 @@ static int read_trusted_verity_root_digests(unsigned int fd)
 
 	p = strim(data);
 	while ((d = strsep(&p, "\n")) != NULL) {
-		int len = strlen(d);
+		int len;
 		struct dm_verity_loadpin_trusted_root_digest *trd;
 
+		if (d == data) {
+			/* first line, validate header */
+			if (strcmp(d, VERITY_DIGEST_FILE_HEADER)) {
+				rc = -EPROTO;
+				goto err;
+			}
+
+			continue;
+		}
+
+		len = strlen(d);
+
 		if (len % 2) {
 			rc = -EPROTO;
 			goto err;