[RFC 1/5] seccomp, x86, arm, mips, s390: Remove nr parameter from secure_computing
Andy Lutomirski
luto at amacapital.net
Wed Jun 11 13:22:58 PDT 2014
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 is 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.
I'm working on a big seccomp speedup for x86, but I'd like to remove
this wart first.
Cc: Russell King <linux at arm.linux.org.uk>
Cc: linux-arm-kernel at lists.infradead.org
Cc: Ralf Baechle <ralf at linux-mips.org>
Cc: linux-mips at linux-mips.org
Cc: Martin Schwidefsky <schwidefsky at de.ibm.com>
Cc: Heiko Carstens <heiko.carstens at de.ibm.com>
Cc: linux-s390 at vger.kernel.org
Cc: x86 at kernel.org
Cc: Kees Cook <keescook at chromium.org>
Signed-off-by: Andy Lutomirski <luto at amacapital.net>
---
arch/arm/kernel/ptrace.c | 7 ++++-
arch/mips/kernel/ptrace.c | 2 +-
arch/s390/kernel/ptrace.c | 2 +-
arch/x86/kernel/ptrace.c | 2 +-
arch/x86/kernel/vsyscall_64.c | 2 +-
include/linux/seccomp.h | 21 ++++++++-------
kernel/seccomp.c | 63 ++++++++++++++++++++++++++++++-------------
7 files changed, 65 insertions(+), 34 deletions(-)
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 0dd3b79..f79c9cc 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -934,8 +934,13 @@ 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))
scno = tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
index f639ccd..808bafc 100644
--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -639,7 +639,7 @@ 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) &&
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 1c82619..20f1998 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -795,7 +795,7 @@ 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;
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 678c0ad..93c182a 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -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;
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 8b3b3eb..47a4123 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -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");
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index 4054b09..6e655a6 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -25,19 +25,17 @@ 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 *);
@@ -54,8 +52,11 @@ 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)
{
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index b35c215..4af399a 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -21,8 +21,11 @@
/* #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/ptrace.h>
#include <linux/security.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;
struct seccomp_data sd;
@@ -372,32 +375,53 @@ 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)
{
int mode = current->seccomp.mode;
+ struct pt_regs *regs = task_pt_regs(current);
+ int this_syscall = syscall_get_nr(current, regs);
int exit_sig = 0;
- int *syscall;
u32 ret;
switch (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) {
@@ -455,9 +479,10 @@ 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)
{
--
1.9.3
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