Merge tag 'hardening-v6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull kernel hardening updates from Kees Cook:

 - Convert flexible array members, fix -Wstringop-overflow warnings, and
   fix KCFI function type mismatches that went ignored by maintainers
   (Gustavo A. R. Silva, Nathan Chancellor, Kees Cook)

 - Remove the remaining side-effect users of ksize() by converting
   dma-buf, btrfs, and coredump to using kmalloc_size_roundup(), add
   more __alloc_size attributes, and introduce full testing of all
   allocator functions. Finally remove the ksize() side-effect so that
   each allocation-aware checker can finally behave without exceptions

 - Introduce oops_limit (default 10,000) and warn_limit (default off) to
   provide greater granularity of control for panic_on_oops and
   panic_on_warn (Jann Horn, Kees Cook)

 - Introduce overflows_type() and castable_to_type() helpers for cleaner
   overflow checking

 - Improve code generation for strscpy() and update str*() kern-doc

 - Convert strscpy and sigphash tests to KUnit, and expand memcpy tests

 - Always use a non-NULL argument for prepare_kernel_cred()

 - Disable structleak plugin in FORTIFY KUnit test (Anders Roxell)

 - Adjust orphan linker section checking to respect CONFIG_WERROR (Xin
   Li)

 - Make sure siginfo is cleared for forced SIGKILL (haifeng.xu)

 - Fix um vs FORTIFY warnings for always-NULL arguments

* tag 'hardening-v6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (31 commits)
  ksmbd: replace one-element arrays with flexible-array members
  hpet: Replace one-element array with flexible-array member
  um: virt-pci: Avoid GCC non-NULL warning
  signal: Initialize the info in ksignal
  lib: fortify_kunit: build without structleak plugin
  panic: Expose "warn_count" to sysfs
  panic: Introduce warn_limit
  panic: Consolidate open-coded panic_on_warn checks
  exit: Allow oops_limit to be disabled
  exit: Expose "oops_count" to sysfs
  exit: Put an upper limit on how often we can oops
  panic: Separate sysctl logic from CONFIG_SMP
  mm/pgtable: Fix multiple -Wstringop-overflow warnings
  mm: Make ksize() a reporting-only function
  kunit/fortify: Validate __alloc_size attribute results
  drm/sti: Fix return type of sti_{dvo,hda,hdmi}_connector_mode_valid()
  drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode_valid()
  driver core: Add __alloc_size hint to devm allocators
  overflow: Introduce overflows_type() and castable_to_type()
  coredump: Proactively round up to kmalloc bucket size
  ...

1 files changed, 7 insertions, 8 deletions

diff --git a/kernel/cred.c b/kernel/cred.c
index e10c15f51c1f..811ad654abd1 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -701,9 +701,9 @@ void __init cred_init(void)
  * override a task's own credentials so that work can be done on behalf of that
  * task that requires a different subjective context.
  *
- * @daemon is used to provide a base for the security record, but can be NULL.
- * If @daemon is supplied, then the security data will be derived from that;
- * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
+ * @daemon is used to provide a base cred, with the security data derived from
+ * that; if this is "&init_task", they'll be set to 0, no groups, full
+ * capabilities, and no keys.
  *
  * The caller may change these controls afterwards if desired.
  *
@@ -714,17 +714,16 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
 	const struct cred *old;
 	struct cred *new;
 
+	if (WARN_ON_ONCE(!daemon))
+		return NULL;
+
 	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 	if (!new)
 		return NULL;
 
 	kdebug("prepare_kernel_cred() alloc %p", new);
 
-	if (daemon)
-		old = get_task_cred(daemon);
-	else
-		old = get_cred(&init_cred);
-
+	old = get_task_cred(daemon);
 	validate_creds(old);
 
 	*new = *old;