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seccomp: Migrate to use SYSCALL_WORK flag

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On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.

Define SYSCALL_WORK_SECCOMP, use it in the generic entry code and convert
the code which uses the TIF specific helper functions to use the new
*_syscall_work() helpers which either resolve to the new mode for users of
the generic entry code or to the TIF based functions for the other
architectures.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-5-krisman@collabora.com
This commit is contained in:
Gabriel Krisman Bertazi 2020-11-16 12:42:00 -05:00 committed by Thomas Gleixner
parent b86678cf0f
commit 23d67a5485
7 changed files with 15 additions and 13 deletions
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2
include/asm-generic/syscall.h
View File

@ -135,7 +135,7 @@ void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
* Returns the AUDIT_ARCH_* based on the system call convention in use.
*
* It's only valid to call this when @task is stopped on entry to a system
* call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %TIF_SECCOMP.
* call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %SYSCALL_WORK_SECCOMP.
*
* Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must
* provide an implementation of this.

8
include/linux/entry-common.h
View File

@ -21,10 +21,6 @@
# define _TIF_SYSCALL_TRACEPOINT (0)
#endif
#ifndef _TIF_SECCOMP
# define _TIF_SECCOMP (0)
#endif
#ifndef _TIF_SYSCALL_AUDIT
# define _TIF_SYSCALL_AUDIT (0)
#endif
@ -49,7 +45,7 @@
#endif
#define SYSCALL_ENTER_WORK \
(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \
(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
_TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_EMU | \
ARCH_SYSCALL_ENTER_WORK)
@ -64,7 +60,7 @@
(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
_TIF_SYSCALL_TRACEPOINT | ARCH_SYSCALL_EXIT_WORK)
#define SYSCALL_WORK_ENTER (0)
#define SYSCALL_WORK_ENTER (SYSCALL_WORK_SECCOMP)
#define SYSCALL_WORK_EXIT (0)
/*

2
include/linux/seccomp.h
View File

@ -42,7 +42,7 @@ struct seccomp {
extern int __secure_computing(const struct seccomp_data *sd);
static inline int secure_computing(void)
{
if (unlikely(test_thread_flag(TIF_SECCOMP)))
if (unlikely(test_syscall_work(SECCOMP)))
return __secure_computing(NULL);
return 0;
}

6
include/linux/thread_info.h
View File

@ -35,6 +35,12 @@ enum {
GOOD_STACK,
};
enum syscall_work_bit {
SYSCALL_WORK_BIT_SECCOMP,
};
#define SYSCALL_WORK_SECCOMP BIT(SYSCALL_WORK_BIT_SECCOMP)
#include <asm/thread_info.h>
#ifdef __KERNEL__

2
kernel/entry/common.c
View File

@ -54,7 +54,7 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall,
}
/* Do seccomp after ptrace, to catch any tracer changes. */
if (ti_work & _TIF_SECCOMP) {
if (work & SYSCALL_WORK_SECCOMP) {
ret = __secure_computing(NULL);
if (ret == -1L)
return ret;

2
kernel/fork.c
View File

@ -1625,7 +1625,7 @@ static void copy_seccomp(struct task_struct *p)
* to manually enable the seccomp thread flag here.
*/
if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
set_tsk_thread_flag(p, TIF_SECCOMP);
set_task_syscall_work(p, SECCOMP);
#endif
}

6
kernel/seccomp.c
View File

@ -356,14 +356,14 @@ static inline void seccomp_assign_mode(struct task_struct *task,
task->seccomp.mode = seccomp_mode;
/*
* Make sure TIF_SECCOMP cannot be set before the mode (and
* Make sure SYSCALL_WORK_SECCOMP cannot be set before the mode (and
* filter) is set.
*/
smp_mb__before_atomic();
/* Assume default seccomp processes want spec flaw mitigation. */
if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0)
arch_seccomp_spec_mitigate(task);
set_tsk_thread_flag(task, TIF_SECCOMP);
set_task_syscall_work(task, SECCOMP);
}
#ifdef CONFIG_SECCOMP_FILTER
@ -929,7 +929,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
/*
* Make sure that any changes to mode from another thread have
* been seen after TIF_SECCOMP was seen.
* been seen after SYSCALL_WORK_SECCOMP was seen.
*/
rmb();