~~ Only this file changed from v15. However, the whole v16 series may be pulled from https://github.com/redpig/linux/tree/seccomp%2Fv16%2Fposted The seccomp/v16/posted tag is GPG-signed. ~~ 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, via PTRACE_EVENT_SECCOMP, 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 tracer with PTRACE_O_TRACESECCOMP 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. v16: - update PT_TRACE_MASK to 0xbf4 so that STOP isn't clear on SETOPTIONS call (indan@xxxxxx) [Note, PT_TRACE_MASK disappears in linux-next] v15: - add audit support for non-zero return codes - clean up style (indan@xxxxxx) v14: - rebase/nochanges v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc (Brings back a change to ptrace.c and the masks.) v12: - rebase to linux-next - use ptrace_event and update arch/Kconfig to mention slow-path dependency - drop all tracehook changes and inclusion (oleg@xxxxxxxxxx) v11: - invert the logic to just make it a PTRACE_SYSCALL accelerator (indan@xxxxxx) 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@xxxxxxxxxxxx> --- arch/Kconfig | 11 ++++++----- include/linux/ptrace.h | 7 +++++-- include/linux/seccomp.h | 1 + kernel/ptrace.c | 3 +++ kernel/seccomp.c | 13 +++++++++++-- 5 files changed, 26 insertions(+), 9 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index d92a78e..3f8132c 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -202,15 +202,16 @@ config HAVE_CMPXCHG_DOUBLE 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 diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index c2f1f6a..3bf7ee9 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -62,8 +62,9 @@ #define PTRACE_O_TRACEEXEC 0x00000010 #define PTRACE_O_TRACEVFORKDONE 0x00000020 #define PTRACE_O_TRACEEXIT 0x00000040 +#define PTRACE_O_TRACESECCOMP 0x00000080 -#define PTRACE_O_MASK 0x0000007f +#define PTRACE_O_MASK 0x000000ff /* Wait extended result codes for the above trace options. */ #define PTRACE_EVENT_FORK 1 @@ -73,6 +74,7 @@ #define PTRACE_EVENT_VFORK_DONE 5 #define PTRACE_EVENT_EXIT 6 #define PTRACE_EVENT_STOP 7 +#define PTRACE_EVENT_SECCOMP 8 #include <asm/ptrace.h> @@ -101,8 +103,9 @@ #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) -#define PT_TRACE_MASK 0x000003f4 +#define PT_TRACE_MASK 0x00000bf4 /* single stepping state bits (used on ARM and PA-RISC) */ #define PT_SINGLESTEP_BIT 31 diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h index a5078fb..306733e 100644 --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -21,6 +21,7 @@ #define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */ #define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */ #define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ +#define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */ #define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ /* Masks for the return value sections. */ diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 00ab2ca..8cf6da1 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -551,6 +551,9 @@ static int ptrace_setoptions(struct task_struct *child, unsigned long data) if (data & PTRACE_O_TRACEEXIT) child->ptrace |= PT_TRACE_EXIT; + if (data & PTRACE_O_TRACESECCOMP) + child->ptrace |= PT_TRACE_SECCOMP; + return (data & ~PTRACE_O_MASK) ? -EINVAL : 0; } diff --git a/kernel/seccomp.c b/kernel/seccomp.c index fb3b993..725e83e 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -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 */ @@ -398,7 +398,7 @@ int __secure_computing_int(int this_syscall) case SECCOMP_MODE_FILTER: ret = seccomp_run_filters(this_syscall); data = ret & SECCOMP_RET_DATA; - switch (code & SECCOMP_RET_ACTION) { + switch (ret & SECCOMP_RET_ACTION) { case SECCOMP_RET_ERRNO: /* Set the low-order 16-bits as a errno. */ syscall_set_return_value(current, task_pt_regs(current), @@ -410,6 +410,15 @@ int __secure_computing_int(int this_syscall) /* Let the filter pass back 16 bits of data. */ seccomp_send_sigsys(this_syscall, data); goto skip; + case SECCOMP_RET_TRACE: + /* Skip these calls if there is no tracer. */ + if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) + goto skip; + /* Allow the BPF to provide the event message */ + ptrace_event(PTRACE_EVENT_SECCOMP, data); + if (fatal_signal_pending(current)) + break; + return 0; case SECCOMP_RET_ALLOW: return 0; case SECCOMP_RET_KILL: -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
