Merge tag 'hardening-v6.10-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull hardening fixes from Kees Cook:

 - Remove invalid tty __counted_by annotation (Nathan Chancellor)

 - Add missing MODULE_DESCRIPTION()s for KUnit string tests (Jeff
   Johnson)

 - Remove non-functional per-arch kstack entropy filtering

* tag 'hardening-v6.10-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  tty: mxser: Remove __counted_by from mxser_board.ports[]
  randomize_kstack: Remove non-functional per-arch entropy filtering
  string: kunit: add missing MODULE_DESCRIPTION() macros

3 files changed, 14 insertions, 19 deletions

diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index ad198262b981..7230f6e20ab8 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -53,17 +53,15 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 	syscall_set_return_value(current, regs, 0, ret);
 
 	/*
-	 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
-	 * but not enough for arm64 stack utilization comfort. To keep
-	 * reasonable stack head room, reduce the maximum offset to 9 bits.
+	 * This value will get limited by KSTACK_OFFSET_MAX(), which is 10
+	 * bits. The actual entropy will be further reduced by the compiler
+	 * when applying stack alignment constraints: the AAPCS mandates a
+	 * 16-byte aligned SP at function boundaries, which will remove the
+	 * 4 low bits from any entropy chosen here.
 	 *
-	 * The actual entropy will be further reduced by the compiler when
-	 * applying stack alignment constraints: the AAPCS mandates a
-	 * 16-byte (i.e. 4-bit) aligned SP at function boundaries.
-	 *
-	 * The resulting 5 bits of entropy is seen in SP[8:4].
+	 * The resulting 6 bits of entropy is seen in SP[9:4].
 	 */
-	choose_random_kstack_offset(get_random_u16() & 0x1FF);
+	choose_random_kstack_offset(get_random_u16());
 }
 
 static inline bool has_syscall_work(unsigned long flags)
diff --git a/arch/s390/include/asm/entry-common.h b/arch/s390/include/asm/entry-common.h
index 7f5004065e8a..35555c944630 100644
--- a/arch/s390/include/asm/entry-common.h
+++ b/arch/s390/include/asm/entry-common.h
@@ -54,7 +54,7 @@ static __always_inline void arch_exit_to_user_mode(void)
 static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
 						  unsigned long ti_work)
 {
-	choose_random_kstack_offset(get_tod_clock_fast() & 0xff);
+	choose_random_kstack_offset(get_tod_clock_fast());
 }
 
 #define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare
diff --git a/arch/x86/include/asm/entry-common.h b/arch/x86/include/asm/entry-common.h
index 7e523bb3d2d3..fb2809b20b0a 100644
--- a/arch/x86/include/asm/entry-common.h
+++ b/arch/x86/include/asm/entry-common.h
@@ -73,19 +73,16 @@ static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
 #endif
 
 	/*
-	 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
-	 * but not enough for x86 stack utilization comfort. To keep
-	 * reasonable stack head room, reduce the maximum offset to 8 bits.
-	 *
-	 * The actual entropy will be further reduced by the compiler when
-	 * applying stack alignment constraints (see cc_stack_align4/8 in
+	 * This value will get limited by KSTACK_OFFSET_MAX(), which is 10
+	 * bits. The actual entropy will be further reduced by the compiler
+	 * when applying stack alignment constraints (see cc_stack_align4/8 in
 	 * arch/x86/Makefile), which will remove the 3 (x86_64) or 2 (ia32)
 	 * low bits from any entropy chosen here.
 	 *
-	 * Therefore, final stack offset entropy will be 5 (x86_64) or
-	 * 6 (ia32) bits.
+	 * Therefore, final stack offset entropy will be 7 (x86_64) or
+	 * 8 (ia32) bits.
 	 */
-	choose_random_kstack_offset(rdtsc() & 0xFF);
+	choose_random_kstack_offset(rdtsc());
 }
 #define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare