Merge tag 'core-entry-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull core entry code update from Thomas Gleixner:
 "A single update to the core entry code, which removes the empty user
  address limit check which is a leftover of the removed TIF_FSCHECK"

* tag 'core-entry-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  entry: Remove empty addr_limit_user_check()

2 files changed, 1 insertions, 18 deletions

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 5690aef7b3a855..c0cb22cd607dc6 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -284,22 +284,6 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
 #endif
 
 /*
- * Called before coming back to user-mode. Returning to user-mode with an
- * address limit different than USER_DS can allow to overwrite kernel memory.
- */
-static inline void addr_limit_user_check(void)
-{
-#ifdef TIF_FSCHECK
-	if (!test_thread_flag(TIF_FSCHECK))
-		return;
-#endif
-
-#ifdef TIF_FSCHECK
-	clear_thread_flag(TIF_FSCHECK);
-#endif
-}
-
-/*
  * These syscall function prototypes are kept in the same order as
  * include/uapi/asm-generic/unistd.h. Architecture specific entries go below,
  * followed by deprecated or obsolete system calls.
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index be61332c66b54a..d7ee4bc3f2ba3e 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -205,8 +205,7 @@ static void exit_to_user_mode_prepare(struct pt_regs *regs)
 
 	arch_exit_to_user_mode_prepare(regs, ti_work);
 
-	/* Ensure that the address limit is intact and no locks are held */
-	addr_limit_user_check();
+	/* Ensure that kernel state is sane for a return to userspace */
 	kmap_assert_nomap();
 	lockdep_assert_irqs_disabled();
 	lockdep_sys_exit();