[tip: core/entry] seccomp: Migrate to use SYSCALL_WORK flag

tip-bot2 for Gabriel Krisman Bertazi
2020-11-16T21:11:59Z

The following commit has been merged into the core/entry branch of tip:

Commit-ID: 23d67a54857a768acdb0804cdd6037c324a50ecd
Gitweb: https://git.kernel.org/tip/23d67a54857a768acdb0804cdd6037c324a50ecd
Author: Gabriel Krisman Bertazi <krisman@collabora.com>
AuthorDate: Mon, 16 Nov 2020 12:42:00 -05:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Mon, 16 Nov 2020 21:53:15 +01:00

seccomp: Migrate to use SYSCALL_WORK flag

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
---
include/asm-generic/syscall.h | 2 +-
include/linux/entry-common.h | 8 ++------
include/linux/seccomp.h | 2 +-
include/linux/thread_info.h | 6 ++++++
kernel/entry/common.c | 2 +-
kernel/fork.c | 2 +-
kernel/seccomp.c | 6 +++---
7 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index f3135e7..524d8e6 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -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.
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 3fe8f86..fa3cdb1 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -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)

/*
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index 02aef28..47763f3 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -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;
}
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 0e9fb15..a308ba4 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -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__
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index e7a11e3..5747a6e 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -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;
diff --git a/kernel/fork.c b/kernel/fork.c
index 32083db..bc5b109 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -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
}

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 8ad7a29..f67e92d 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -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();