@@ -236,15 +236,16 @@ config ARCH_WANT_OLD_COMPAT_IPC
config HAVE_ARCH_SECCOMP_FILTER
bool
help
- This symbol should be selected by an architecure if it provides:
- asm/syscall.h:
+ An arch should select this symbol if it provides all of these things:
- syscall_get_arch()
- syscall_get_arguments()
- syscall_rollback()
- syscall_set_return_value()
- SIGSYS siginfo_t support must be implemented.
- __secure_computing_int()/secure_computing()'s return value must be
- checked, with -1 resulting in the syscall being skipped.
+ - SIGSYS siginfo_t support
+ - uses __secure_computing_int() or secure_computing()
+ - secure_computing is called from a ptrace_event()-safe context
+ - secure_computing return value is checked and a return value of -1
+ results in the system call being skipped immediately.
config SECCOMP_FILTER
def_bool y
@@ -58,6 +58,7 @@
#define PTRACE_EVENT_EXEC 4
#define PTRACE_EVENT_VFORK_DONE 5
#define PTRACE_EVENT_EXIT 6
+#define PTRACE_EVENT_SECCOMP 7
/* Extended result codes which enabled by means other than options. */
#define PTRACE_EVENT_STOP 128
@@ -69,8 +70,9 @@
#define PTRACE_O_TRACEEXEC (1 << PTRACE_EVENT_EXEC)
#define PTRACE_O_TRACEVFORKDONE (1 << PTRACE_EVENT_VFORK_DONE)
#define PTRACE_O_TRACEEXIT (1 << PTRACE_EVENT_EXIT)
+#define PTRACE_O_TRACESECCOMP (1 << PTRACE_EVENT_SECCOMP)
-#define PTRACE_O_MASK 0x0000007f
+#define PTRACE_O_MASK 0x000000ff
#include <asm/ptrace.h>
@@ -98,6 +100,7 @@
#define PT_TRACE_EXEC PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
#define PT_TRACE_VFORK_DONE PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
#define PT_TRACE_EXIT PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
+#define PT_TRACE_SECCOMP PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
/* single stepping state bits (used on ARM and PA-RISC) */
#define PT_SINGLESTEP_BIT 31
@@ -21,6 +21,7 @@
#define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */
#define SECCOMP_RET_TRAP 0x00020000U /* disallow and force a SIGSYS */
#define SECCOMP_RET_ERRNO 0x00030000U /* returns an errno */
+#define SECCOMP_RET_TRACE 0x7ffe0000U /* pass to a tracer or disallow */
#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */
/* Masks for the return value sections. */
@@ -17,13 +17,13 @@
#include <linux/audit.h>
#include <linux/compat.h>
#include <linux/filter.h>
+#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/seccomp.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
-#include <linux/tracehook.h>
#include <asm/syscall.h>
/* #define SECCOMP_DEBUG 1 */
@@ -346,14 +346,24 @@ int __secure_computing_int(int this_syscall)
-(action & SECCOMP_RET_DATA),
0);
return -1;
- case SECCOMP_RET_TRAP: {
- int reason_code = action & SECCOMP_RET_DATA;
+ case SECCOMP_RET_TRAP:
/* Show the handler the original registers. */
syscall_rollback(current, task_pt_regs(current));
/* Let the filter pass back 16 bits of data. */
- seccomp_send_sigsys(this_syscall, reason_code);
+ seccomp_send_sigsys(this_syscall,
+ action & SECCOMP_RET_DATA);
return -1;
- }
+ case SECCOMP_RET_TRACE:
+ /* Skip these calls if there is no tracer. */
+ if (!ptrace_event_enabled(current,
+ PTRACE_EVENT_SECCOMP))
+ return -1;
+ /* Allow the BPF to provide the event message */
+ ptrace_event(PTRACE_EVENT_SECCOMP,
+ action & SECCOMP_RET_DATA);
+ if (fatal_signal_pending(current))
+ break;
+ return 0;
case SECCOMP_RET_ALLOW:
return 0;
case SECCOMP_RET_KILL:
This change adds support for a new ptrace option, PTRACE_O_TRACESECCOMP, and a new return value for seccomp BPF programs, SECCOMP_RET_TRACE. When a tracer specifies the PTRACE_O_TRACESECCOMP ptrace option, the tracer will be notified for any syscall that results in a BPF program returning SECCOMP_RET_TRACE. The 16-bit SECCOMP_RET_DATA mask of the BPF program return value will be passed as the ptrace_message and may be retrieved using PTRACE_GETEVENTMSG. If the subordinate process is not using seccomp filter, then no system call notifications will occur even if the option is specified. If there is no attached tracer when SECCOMP_RET_TRACE is returned, the system call will not be executed and an -ENOSYS errno will be returned to userspace. This change adds a dependency on the system call slow path. Any future efforts to use the system call fast path for seccomp filter will need to address this restriction. v12: - rebase to linux-next - use ptrace_event and update arch/Kconfig to mention slow-path dependency - drop all tracehook changes and inclusion (oleg@redhat.com) v11: - invert the logic to just make it a PTRACE_SYSCALL accelerator (indan@nul.nu) v10: - moved to PTRACE_O_SECCOMP / PT_TRACE_SECCOMP v9: - n/a v8: - guarded PTRACE_SECCOMP use with an ifdef v7: - introduced Signed-off-by: Will Drewry <wad@chromium.org> --- arch/Kconfig | 11 ++++++----- include/linux/ptrace.h | 5 ++++- include/linux/seccomp.h | 1 + kernel/seccomp.c | 20 +++++++++++++++----- 4 files changed, 26 insertions(+), 11 deletions(-)