From c50b4659e444b020657e01bdf769c965e5597cb0 Mon Sep 17 00:00:00 2001 From: Mickaël Salaün Date: Tue, 29 Dec 2015 21:35:47 +0100 Subject: um: Add seccomp support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This brings SECCOMP_MODE_STRICT and SECCOMP_MODE_FILTER support through prctl(2) and seccomp(2) to User-mode Linux for i386 and x86_64 subarchitectures. secure_computing() is called first in handle_syscall() so that the syscall emulation will be aborted quickly if matching a seccomp rule. This is inspired from Meredydd Luff's patch (https://gerrit.chromium.org/gerrit/21425). Signed-off-by: Mickaël Salaün Cc: Jeff Dike Cc: Richard Weinberger Cc: Ingo Molnar Cc: Kees Cook Cc: Andy Lutomirski Cc: Will Drewry Cc: Chris Metcalf Cc: Michael Ellerman Cc: James Hogan Cc: Meredydd Luff Cc: David Drysdale Signed-off-by: Richard Weinberger Acked-by: Kees Cook --- arch/um/Kconfig.common | 1 + arch/um/Kconfig.um | 16 ++++++++++++++++ arch/um/include/asm/thread_info.h | 2 ++ arch/um/kernel/skas/syscall.c | 5 +++++ 4 files changed, 24 insertions(+) (limited to 'arch/um') diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common index d195a87ca542..cc0013475444 100644 --- a/arch/um/Kconfig.common +++ b/arch/um/Kconfig.common @@ -2,6 +2,7 @@ config UML bool default y select HAVE_ARCH_AUDITSYSCALL + select HAVE_ARCH_SECCOMP_FILTER select HAVE_UID16 select HAVE_FUTEX_CMPXCHG if FUTEX select GENERIC_IRQ_SHOW diff --git a/arch/um/Kconfig.um b/arch/um/Kconfig.um index 28a9885e3a37..4b2ed5858b2e 100644 --- a/arch/um/Kconfig.um +++ b/arch/um/Kconfig.um @@ -104,3 +104,19 @@ config PGTABLE_LEVELS int default 3 if 3_LEVEL_PGTABLES default 2 + +config SECCOMP + def_bool y + prompt "Enable seccomp to safely compute untrusted bytecode" + ---help--- + This kernel feature is useful for number crunching applications + that may need to compute untrusted bytecode during their + execution. By using pipes or other transports made available to + the process as file descriptors supporting the read/write + syscalls, it's possible to isolate those applications in + their own address space using seccomp. Once seccomp is + enabled via prctl(PR_SET_SECCOMP), it cannot be disabled + and the task is only allowed to execute a few safe syscalls + defined by each seccomp mode. + + If unsure, say Y. diff --git a/arch/um/include/asm/thread_info.h b/arch/um/include/asm/thread_info.h index 53968aaf76f9..053baff03674 100644 --- a/arch/um/include/asm/thread_info.h +++ b/arch/um/include/asm/thread_info.h @@ -62,11 +62,13 @@ static inline struct thread_info *current_thread_info(void) #define TIF_SYSCALL_AUDIT 6 #define TIF_RESTORE_SIGMASK 7 #define TIF_NOTIFY_RESUME 8 +#define TIF_SECCOMP 9 /* secure computing */ #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE) #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) #define _TIF_MEMDIE (1 << TIF_MEMDIE) #define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT) +#define _TIF_SECCOMP (1 << TIF_SECCOMP) #endif diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c index 6cadce761bcf..48b0dcbd87be 100644 --- a/arch/um/kernel/skas/syscall.c +++ b/arch/um/kernel/skas/syscall.c @@ -5,6 +5,7 @@ #include #include +#include #include #include #include @@ -19,6 +20,10 @@ void handle_syscall(struct uml_pt_regs *r) UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp); PT_REGS_SET_SYSCALL_RETURN(regs, -ENOSYS); + /* Do the secure computing check first; failures should be fast. */ + if (secure_computing() == -1) + return; + if (syscall_trace_enter(regs)) goto out; -- cgit v1.2.3-59-g8ed1b