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seccomp: remove 2-phase API 

Since nothing is using the 2-phase API, and it adds more complexity than
benefit, remove it.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
This commit is contained in:
Kees Cook 2016-06-01 16:02:17 -07:00
parent c87a85177e
commit 8112c4f140
2 changed files with 41 additions and 94 deletions
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6
include/linux/seccomp.h
View File

@ -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

155
kernel/seccomp.c
View File

@ -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;
@ -599,94 +588,12 @@ 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. */
case SECCOMP_RET_ALLOW:
return SECCOMP_PHASE1_OK;
case SECCOMP_RET_KILL:
default:
audit_seccomp(this_syscall, SIGSYS, action);
do_exit(SIGSYS);
}
unreachable();
skip:
audit_seccomp(this_syscall, 0, action);
return SECCOMP_PHASE1_SKIP;
}
#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 mode = current->seccomp.mode;
int this_syscall = sd ? sd->nr :
syscall_get_nr(current, task_pt_regs(current));
if (config_enabled(CONFIG_CHECKPOINT_RESTORE) &&
unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
return SECCOMP_PHASE1_OK;
switch (mode) {
case SECCOMP_MODE_STRICT:
__secure_computing_strict(this_syscall); /* may call do_exit */
return SECCOMP_PHASE1_OK;
#ifdef CONFIG_SECCOMP_FILTER
case SECCOMP_MODE_FILTER:
return __seccomp_phase1_filter(this_syscall, sd);
#endif
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. */
/* ENOSYS these calls if there is no tracer attached. */
if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
syscall_set_return_value(current, regs,
syscall_set_return_value(current,
task_pt_regs(current),
-ENOSYS, 0);
return -1;
goto skip;
}
/* Allow the BPF to provide the event message */
@ -699,10 +606,56 @@ int seccomp_phase2(u32 phase1_result)
*/
if (fatal_signal_pending(current))
do_exit(SIGSYS);
if (syscall_get_nr(current, regs) < 0)
return -1; /* Explicit request to skip. */
/* 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 0;
case SECCOMP_RET_KILL:
default:
audit_seccomp(this_syscall, SIGSYS, action);
do_exit(SIGSYS);
}
unreachable();
skip:
audit_seccomp(this_syscall, 0, action);
return -1;
}
#else
static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd)
{
BUG();
}
#endif
int __secure_computing(const struct seccomp_data *sd)
{
int mode = current->seccomp.mode;
int this_syscall;
if (config_enabled(CONFIG_CHECKPOINT_RESTORE) &&
unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
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 0;
case SECCOMP_MODE_FILTER:
return __seccomp_filter(this_syscall, sd);
default:
BUG();
}
}
#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */