[PATCH 04/14] seccomp: remove 2-phase API
Kees Cook
keescook at chromium.org
Fri Jun 10 07:01:54 AEST 2016
Since nothing is using the 2-phase API, and it adds more complexity than
benefit, remove it.
Signed-off-by: Kees Cook <keescook at chromium.org>
Cc: Andy Lutomirski <luto at kernel.org>
---
include/linux/seccomp.h | 6 ---
kernel/seccomp.c | 129 +++++++++++++++---------------------------------
2 files changed, 41 insertions(+), 94 deletions(-)
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index 9eaa7b34d6da..ecc296c137cd 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -35,12 +35,6 @@ static inline int secure_computing(const struct seccomp_data *sd)
return __secure_computing(sd);
return 0;
}
-
-#define SECCOMP_PHASE1_OK 0
-#define SECCOMP_PHASE1_SKIP 1
-
-extern u32 seccomp_phase1(struct seccomp_data *sd);
-int seccomp_phase2(u32 phase1_result);
#else
extern void secure_computing_strict(int this_syscall);
#endif
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 06816290a212..14a37d71b612 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -173,7 +173,7 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
*
* Returns valid seccomp BPF response codes.
*/
-static u32 seccomp_run_filters(struct seccomp_data *sd)
+static u32 seccomp_run_filters(const struct seccomp_data *sd)
{
struct seccomp_data sd_local;
u32 ret = SECCOMP_RET_ALLOW;
@@ -554,20 +554,9 @@ void secure_computing_strict(int this_syscall)
BUG();
}
#else
-int __secure_computing(const struct seccomp_data *sd)
-{
- u32 phase1_result = seccomp_phase1(sd);
-
- if (likely(phase1_result == SECCOMP_PHASE1_OK))
- return 0;
- else if (likely(phase1_result == SECCOMP_PHASE1_SKIP))
- return -1;
- else
- return seccomp_phase2(phase1_result);
-}
#ifdef CONFIG_SECCOMP_FILTER
-static u32 __seccomp_phase1_filter(int this_syscall, struct seccomp_data *sd)
+static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd)
{
u32 filter_ret, action;
int data;
@@ -599,10 +588,33 @@ static u32 __seccomp_phase1_filter(int this_syscall, struct seccomp_data *sd)
goto skip;
case SECCOMP_RET_TRACE:
- return filter_ret; /* Save the rest for phase 2. */
+ /* ENOSYS these calls if there is no tracer attached. */
+ if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
+ syscall_set_return_value(current,
+ task_pt_regs(current),
+ -ENOSYS, 0);
+ goto skip;
+ }
+
+ /* Allow the BPF to provide the event message */
+ ptrace_event(PTRACE_EVENT_SECCOMP, data);
+ /*
+ * The delivery of a fatal signal during event
+ * notification may silently skip tracer notification.
+ * Terminating the task now avoids executing a system
+ * call that may not be intended.
+ */
+ if (fatal_signal_pending(current))
+ do_exit(SIGSYS);
+ /* Check if the tracer forced the syscall to be skipped. */
+ this_syscall = syscall_get_nr(current, task_pt_regs(current));
+ if (this_syscall < 0)
+ goto skip;
+
+ return 0;
case SECCOMP_RET_ALLOW:
- return SECCOMP_PHASE1_OK;
+ return 0;
case SECCOMP_RET_KILL:
default:
@@ -614,96 +626,37 @@ static u32 __seccomp_phase1_filter(int this_syscall, struct seccomp_data *sd)
skip:
audit_seccomp(this_syscall, 0, action);
- return SECCOMP_PHASE1_SKIP;
+ return -1;
+}
+#else
+static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd)
+{
+ BUG();
}
#endif
-/**
- * seccomp_phase1() - run fast path seccomp checks on the current syscall
- * @arg sd: The seccomp_data or NULL
- *
- * This only reads pt_regs via the syscall_xyz helpers. The only change
- * it will make to pt_regs is via syscall_set_return_value, and it will
- * only do that if it returns SECCOMP_PHASE1_SKIP.
- *
- * If sd is provided, it will not read pt_regs at all.
- *
- * It may also call do_exit or force a signal; these actions must be
- * safe.
- *
- * If it returns SECCOMP_PHASE1_OK, the syscall passes checks and should
- * be processed normally.
- *
- * If it returns SECCOMP_PHASE1_SKIP, then the syscall should not be
- * invoked. In this case, seccomp_phase1 will have set the return value
- * using syscall_set_return_value.
- *
- * If it returns anything else, then the return value should be passed
- * to seccomp_phase2 from a context in which ptrace hooks are safe.
- */
-u32 seccomp_phase1(struct seccomp_data *sd)
+int __secure_computing(const struct seccomp_data *sd)
{
int mode = current->seccomp.mode;
- int this_syscall = sd ? sd->nr :
- syscall_get_nr(current, task_pt_regs(current));
+ int this_syscall;
if (config_enabled(CONFIG_CHECKPOINT_RESTORE) &&
unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
- return SECCOMP_PHASE1_OK;
+ return 0;
+
+ this_syscall = sd ? sd->nr :
+ syscall_get_nr(current, task_pt_regs(current));
switch (mode) {
case SECCOMP_MODE_STRICT:
__secure_computing_strict(this_syscall); /* may call do_exit */
- return SECCOMP_PHASE1_OK;
-#ifdef CONFIG_SECCOMP_FILTER
+ return 0;
case SECCOMP_MODE_FILTER:
- return __seccomp_phase1_filter(this_syscall, sd);
-#endif
+ return __seccomp_filter(this_syscall, sd);
default:
BUG();
}
}
-
-/**
- * seccomp_phase2() - finish slow path seccomp work for the current syscall
- * @phase1_result: The return value from seccomp_phase1()
- *
- * This must be called from a context in which ptrace hooks can be used.
- *
- * Returns 0 if the syscall should be processed or -1 to skip the syscall.
- */
-int seccomp_phase2(u32 phase1_result)
-{
- struct pt_regs *regs = task_pt_regs(current);
- u32 action = phase1_result & SECCOMP_RET_ACTION;
- int data = phase1_result & SECCOMP_RET_DATA;
-
- BUG_ON(action != SECCOMP_RET_TRACE);
-
- audit_seccomp(syscall_get_nr(current, regs), 0, action);
-
- /* Skip these calls if there is no tracer. */
- if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
- syscall_set_return_value(current, regs,
- -ENOSYS, 0);
- return -1;
- }
-
- /* Allow the BPF to provide the event message */
- ptrace_event(PTRACE_EVENT_SECCOMP, data);
- /*
- * The delivery of a fatal signal during event
- * notification may silently skip tracer notification.
- * Terminating the task now avoids executing a system
- * call that may not be intended.
- */
- if (fatal_signal_pending(current))
- do_exit(SIGSYS);
- if (syscall_get_nr(current, regs) < 0)
- return -1; /* Explicit request to skip. */
-
- return 0;
-}
#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
long prctl_get_seccomp(void)
--
2.7.4
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