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seccomp,x86,arm,mips,s390: Remove nr parameter from secure_computing 

The secure_computing function took a syscall number parameter, but
it only paid any attention to that parameter if seccomp mode 1 was
enabled.  Rather than coming up with a kludge to get the parameter
to work in mode 2, just remove the parameter.

To avoid churn in arches that don't have seccomp filters (and may
not even support syscall_get_nr right now), this leaves the
parameter in secure_computing_strict, which is now a real function.

For ARM, this is a bit ugly due to the fact that ARM conditionally
supports seccomp filters.  Fixing that would probably only be a
couple of lines of code, but it should be coordinated with the audit
maintainers.

This will be a slight slowdown on some arches.  The right fix is to
pass in all of seccomp_data instead of trying to make just the
syscall nr part be fast.

This is a prerequisite for making two-phase seccomp work cleanly.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-s390@vger.kernel.org
Cc: x86@kernel.org
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Andy Lutomirski 2014-07-21 18:49:14 -07:00 committed by Kees Cook
parent 70c8038dd6
commit a4412fc948
7 changed files with 66 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
arch/arm/kernel/ptrace.c
View File

@ -933,8 +933,13 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
current_thread_info()->syscall = scno;
/* Do the secure computing check first; failures should be fast. */
if (secure_computing(scno) == -1)
#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
if (secure_computing() == -1)
return -1;
#else
/* XXX: remove this once OABI gets fixed */
secure_computing_strict(scno);
#endif
if (test_thread_flag(TIF_SYSCALL_TRACE))
tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);

2
arch/mips/kernel/ptrace.c
View File

@ -770,7 +770,7 @@ asmlinkage long syscall_trace_enter(struct pt_regs *regs, long syscall)
long ret = 0;
user_exit();
if (secure_computing(syscall) == -1)
if (secure_computing() == -1)
return -1;
if (test_thread_flag(TIF_SYSCALL_TRACE) &&

2
arch/s390/kernel/ptrace.c
View File

@ -803,7 +803,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
long ret = 0;
/* Do the secure computing check first. */
if (secure_computing(regs->gprs[2])) {
if (secure_computing()) {
/* seccomp failures shouldn't expose any additional code. */
ret = -1;
goto out;

2
arch/x86/kernel/ptrace.c
View File

@ -1471,7 +1471,7 @@ long syscall_trace_enter(struct pt_regs *regs)
regs->flags |= X86_EFLAGS_TF;
/* do the secure computing check first */
if (secure_computing(regs->orig_ax)) {
if (secure_computing()) {
/* seccomp failures shouldn't expose any additional code. */
ret = -1L;
goto out;

2
arch/x86/kernel/vsyscall_64.c
View File

@ -216,7 +216,7 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
*/
regs->orig_ax = syscall_nr;
regs->ax = -ENOSYS;
tmp = secure_computing(syscall_nr);
tmp = secure_computing();
if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) {
warn_bad_vsyscall(KERN_DEBUG, regs,
"seccomp tried to change syscall nr or ip");

21
include/linux/seccomp.h
View File

@ -27,19 +27,17 @@ struct seccomp {
struct seccomp_filter *filter;
};
extern int __secure_computing(int);
static inline int secure_computing(int this_syscall)
#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
extern int __secure_computing(void);
static inline int secure_computing(void)
{
if (unlikely(test_thread_flag(TIF_SECCOMP)))
return __secure_computing(this_syscall);
return __secure_computing();
return 0;
}
/* A wrapper for architectures supporting only SECCOMP_MODE_STRICT. */
static inline void secure_computing_strict(int this_syscall)
{
BUG_ON(secure_computing(this_syscall) != 0);
}
#else
extern void secure_computing_strict(int this_syscall);
#endif
extern long prctl_get_seccomp(void);
extern long prctl_set_seccomp(unsigned long, char __user *);
@ -56,8 +54,11 @@ static inline int seccomp_mode(struct seccomp *s)
struct seccomp { };
struct seccomp_filter { };
static inline int secure_computing(int this_syscall) { return 0; }
#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
static inline int secure_computing(void) { return 0; }
#else
static inline void secure_computing_strict(int this_syscall) { return; }
#endif
static inline long prctl_get_seccomp(void)
{

64
kernel/seccomp.c
View File

@ -23,8 +23,11 @@
/* #define SECCOMP_DEBUG 1 */
#ifdef CONFIG_SECCOMP_FILTER
#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
#include <asm/syscall.h>
#endif
#ifdef CONFIG_SECCOMP_FILTER
#include <linux/filter.h>
#include <linux/pid.h>
#include <linux/ptrace.h>
@ -172,7 +175,7 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
*
* Returns valid seccomp BPF response codes.
*/
static u32 seccomp_run_filters(int syscall)
static u32 seccomp_run_filters(void)
{
struct seccomp_filter *f = ACCESS_ONCE(current->seccomp.filter);
struct seccomp_data sd;
@ -564,10 +567,43 @@ static int mode1_syscalls_32[] = {
};
#endif
int __secure_computing(int this_syscall)
static void __secure_computing_strict(int this_syscall)
{
int *syscall_whitelist = mode1_syscalls;
#ifdef CONFIG_COMPAT
if (is_compat_task())
syscall_whitelist = mode1_syscalls_32;
#endif
do {
if (*syscall_whitelist == this_syscall)
return;
} while (*++syscall_whitelist);
#ifdef SECCOMP_DEBUG
dump_stack();
#endif
audit_seccomp(this_syscall, SIGKILL, SECCOMP_RET_KILL);
do_exit(SIGKILL);
}
#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
void secure_computing_strict(int this_syscall)
{
int mode = current->seccomp.mode;
if (mode == 0)
return;
else if (mode == SECCOMP_MODE_STRICT)
__secure_computing_strict(this_syscall);
else
BUG();
}
#else
int __secure_computing(void)
{
struct pt_regs *regs = task_pt_regs(current);
int this_syscall = syscall_get_nr(current, regs);
int exit_sig = 0;
int *syscall;
u32 ret;
/*
@ -578,23 +614,12 @@ int __secure_computing(int this_syscall)
switch (current->seccomp.mode) {
case SECCOMP_MODE_STRICT:
syscall = mode1_syscalls;
#ifdef CONFIG_COMPAT
if (is_compat_task())
syscall = mode1_syscalls_32;
#endif
do {
if (*syscall == this_syscall)
return 0;
} while (*++syscall);
exit_sig = SIGKILL;
ret = SECCOMP_RET_KILL;
break;
__secure_computing_strict(this_syscall);
return 0;
#ifdef CONFIG_SECCOMP_FILTER
case SECCOMP_MODE_FILTER: {
int data;
struct pt_regs *regs = task_pt_regs(current);
ret = seccomp_run_filters(this_syscall);
ret = seccomp_run_filters();
data = ret & SECCOMP_RET_DATA;
ret &= SECCOMP_RET_ACTION;
switch (ret) {
@ -652,9 +677,10 @@ int __secure_computing(int this_syscall)
#ifdef CONFIG_SECCOMP_FILTER
skip:
audit_seccomp(this_syscall, exit_sig, ret);
#endif
return -1;
#endif
}
#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
long prctl_get_seccomp(void)
{