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Message-ID: <169277972713.27769.12372205097599743330.tip-bot2@tip-bot2>
Date: Wed, 23 Aug 2023 08:35:27 -0000
From: "tip-bot2 for Mark Rutland" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Mark Rutland <mark.rutland@....com>,
Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: core/entry] entry: Remove empty addr_limit_user_check()
The following commit has been merged into the core/entry branch of tip:
Commit-ID: 1dfe3a5a7cefbe2162cecb759f3933baea22c393
Gitweb: https://git.kernel.org/tip/1dfe3a5a7cefbe2162cecb759f3933baea22c393
Author: Mark Rutland <mark.rutland@....com>
AuthorDate: Mon, 21 Aug 2023 17:35:26 +01:00
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Wed, 23 Aug 2023 10:32:39 +02:00
entry: Remove empty addr_limit_user_check()
Back when set_fs() was a generic API for altering the address limit,
addr_limit_user_check() was a safety measure to prevent userspace being
able to issue syscalls with an unbound limit.
With the the removal of set_fs() as a generic API, the last user of
addr_limit_user_check() was removed in commit:
b5a5a01d8e9a44ec ("arm64: uaccess: remove addr_limit_user_check()")
... as since that commit, no architecture defines TIF_FSCHECK, and hence
addr_limit_user_check() always expands to nothing.
Remove addr_limit_user_check(), updating the comment in
exit_to_user_mode_prepare() to no longer refer to it. At the same time,
the comment is reworded to be a little more generic so as to cover
kmap_assert_nomap() in addition to lockdep_sys_exit().
No functional change.
Signed-off-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/r/20230821163526.2319443-1-mark.rutland@arm.com
---
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 03e3d01..c4b9b66 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 be61332..d7ee4bc 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();
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