linux-kernel - [GIT pull] core/entry for v6.6-rc1

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Message-ID: <169322654636.420889.373907562030292433.tglx@xen13.tec.linutronix.de>
Date:   Mon, 28 Aug 2023 15:01:10 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull] core/entry for v6.6-rc1

Linus,

please pull the latest core/entry branch from:

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

up to:  1dfe3a5a7cef: entry: Remove empty addr_limit_user_check()


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.

Thanks,

	tglx

------------------>
Mark Rutland (1):
      entry: Remove empty addr_limit_user_check()


 include/linux/syscalls.h | 16 ----------------
 kernel/entry/common.c    |  3 +--
 2 files changed, 1 insertion(+), 18 deletions(-)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 03e3d0121d5e..c4b9b66b0d05 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -283,22 +283,6 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
 #define SYSCALL32_DEFINE6 SYSCALL_DEFINE6
 #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,
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index be61332c66b5..d7ee4bc3f2ba 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();