[PATCH v2 08/10] audit: Migrate to use SYSCALL_WORK flag

Gabriel Krisman Bertazi
2020-11-16T17:42:56Z

For architectures that rely on the generic syscall entry code, use the
syscall_work field in struct thread_info and the specific SYSCALL_WORK
flag. This set of flags has the advantage of being architecture
independent.

Users of the flag outside of the generic entry code should rely on the
accessor macros, such that the flag is still correctly resolved for
architectures that don't use the generic entry code and still rely on
TIF flags for system call work.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

---
Changes since v2:
- Drop explicit value assignment in enum (tglx)
- Avoid FLAG/_FLAG defines (tglx)
- Fix comment to refer to SYSCALL_WORK (me)
---
include/asm-generic/syscall.h | 23 ++++++++++++++---------
include/linux/entry-common.h | 18 ++++++------------
include/linux/thread_info.h | 2 ++
kernel/auditsc.c | 4 ++--
4 files changed, 24 insertions(+), 23 deletions(-)

diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index ed94e5658d0c..524218ae3825 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -43,9 +43,9 @@ int syscall_get_nr(struct task_struct *task, struct pt_regs *regs);
* @regs: task_pt_regs() of @task
*
* It's only valid to call this when @task is stopped for system
- * call exit tracing (due to %SYSCALL_WORK_SYSCALL_TRACE or TIF_SYSCALL_AUDIT),
- * after tracehook_report_syscall_entry() returned nonzero to prevent
- * the system call from taking place.
+ * call exit tracing (due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT), after tracehook_report_syscall_entry()
+ * returned nonzero to prevent the system call from taking place.
*
* This rolls back the register state in @regs so it's as if the
* system call instruction was a no-op. The registers containing
@@ -63,7 +63,8 @@ void syscall_rollback(struct task_struct *task, struct pt_regs *regs);
* Returns 0 if the system call succeeded, or -ERRORCODE if it failed.
*
* It's only valid to call this when @task is stopped for tracing on exit
- * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
*/
long syscall_get_error(struct task_struct *task, struct pt_regs *regs);

@@ -76,7 +77,8 @@ long syscall_get_error(struct task_struct *task, struct pt_regs *regs);
* This value is meaningless if syscall_get_error() returned nonzero.
*
* It's only valid to call this when @task is stopped for tracing on exit
- * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
*/
long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);

@@ -93,7 +95,8 @@ long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);
* code; the user sees a failed system call with this errno code.
*
* It's only valid to call this when @task is stopped for tracing on exit
- * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
*/
void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
int error, long val);
@@ -108,7 +111,8 @@ void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
* @args[0], and so on.
*
* It's only valid to call this when @task is stopped for tracing on
- * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
*/
void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
unsigned long *args);
@@ -123,7 +127,8 @@ void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
* The first argument gets value @args[0], and so on.
*
* It's only valid to call this when @task is stopped for tracing on
- * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
*/
void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
const unsigned long *args);
@@ -135,7 +140,7 @@ 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 %SYSCALL_WORK_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or
+ * call, due to %SYSCALL_WORK_SYSCALL_TRACE, %SYSCALL_WORK_SYSCALL_AUDIT, or
* %SYSCALL_WORK_SECCOMP.
*
* Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 39d56558818d..afeb927e8545 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -13,10 +13,6 @@
* Define dummy _TIF work flags if not defined by the architecture or for
* disabled functionality.
*/
-#ifndef _TIF_SYSCALL_AUDIT
-# define _TIF_SYSCALL_AUDIT (0)
-#endif
-
#ifndef _TIF_PATCH_PENDING
# define _TIF_PATCH_PENDING (0)
#endif
@@ -36,9 +32,7 @@
# define ARCH_SYSCALL_ENTER_WORK (0)
#endif

-#define SYSCALL_ENTER_WORK \
- (_TIF_SYSCALL_AUDIT | \
- ARCH_SYSCALL_ENTER_WORK)
+#define SYSCALL_ENTER_WORK ARCH_SYSCALL_ENTER_WORK

/*
* TIF flags handled in syscall_exit_to_user_mode()
@@ -47,16 +41,16 @@
# define ARCH_SYSCALL_EXIT_WORK (0)
#endif

-#define SYSCALL_EXIT_WORK \
- (_TIF_SYSCALL_AUDIT | \
- ARCH_SYSCALL_EXIT_WORK)
+#define SYSCALL_EXIT_WORK ARCH_SYSCALL_EXIT_WORK

#define SYSCALL_WORK_ENTER (SYSCALL_WORK_SECCOMP | \
SYSCALL_WORK_SYSCALL_TRACEPOINT | \
SYSCALL_WORK_SYSCALL_TRACE | \
- SYSCALL_WORK_SYSCALL_EMU)
+ SYSCALL_WORK_SYSCALL_EMU | \
+ SYSCALL_WORK_SYSCALL_AUDIT)
#define SYSCALL_WORK_EXIT (SYSCALL_WORK_SYSCALL_TRACEPOINT | \
- SYSCALL_WORK_SYSCALL_TRACE)
+ SYSCALL_WORK_SYSCALL_TRACE | \
+ SYSCALL_WORK_SYSCALL_AUDIT)

/*
* TIF flags handled in exit_to_user_mode_loop()
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 844c9a102317..6a597fd5d351 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -40,12 +40,14 @@ enum syscall_work_bit {
SYSCALL_WORK_BIT_SYSCALL_TRACEPOINT,
SYSCALL_WORK_BIT_SYSCALL_TRACE,
SYSCALL_WORK_BIT_SYSCALL_EMU,
+ SYSCALL_WORK_BIT_SYSCALL_AUDIT,
};

#define SYSCALL_WORK_SECCOMP BIT(SYSCALL_WORK_BIT_SECCOMP)
#define SYSCALL_WORK_SYSCALL_TRACEPOINT BIT(SYSCALL_WORK_BIT_SYSCALL_TRACEPOINT)
#define SYSCALL_WORK_SYSCALL_TRACE BIT(SYSCALL_WORK_BIT_SYSCALL_TRACE)
#define SYSCALL_WORK_SYSCALL_EMU BIT(SYSCALL_WORK_BIT_SYSCALL_EMU)
+#define SYSCALL_WORK_SYSCALL_AUDIT BIT(SYSCALL_WORK_BIT_SYSCALL_AUDIT)

#include <asm/thread_info.h>

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 8dba8f0983b5..c00aa5837965 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -952,7 +952,7 @@ int audit_alloc(struct task_struct *tsk)

state = audit_filter_task(tsk, &key);
if (state == AUDIT_DISABLED) {
- clear_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
+ clear_task_syscall_work(tsk, SYSCALL_AUDIT);
return 0;
}

@@ -964,7 +964,7 @@ int audit_alloc(struct task_struct *tsk)
context->filterkey = key;

audit_set_context(tsk, context);
- set_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
+ set_task_syscall_work(tsk, SYSCALL_AUDIT);
return 0;
}

--
2.29.2