diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2023-08-21 17:35:26 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2023-08-23 10:32:39 +0200 |
| commit | 1dfe3a5a7cefbe2162cecb759f3933baea22c393 (patch) | |
| tree | f78b2a7b553e2feb8ebe183ac97413f4e7b3c6a5 | |
| parent | 6eaae198076080886b9e7d57f4ae06fa782f90ef (diff) | |
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@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230821163526.2319443-1-mark.rutland@arm.com
| -rw-r--r-- | include/linux/syscalls.h | 16 | ||||
| -rw-r--r-- | kernel/entry/common.c | 3 |
2 files changed, 1 insertions, 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 @@ -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 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(); |