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 <mic@xxxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Jeff Dike <jdike@xxxxxxxxxxx> Cc: Richard Weinberger <richard@xxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Will Drewry <wad@xxxxxxxxxxxx> Cc: Chris Metcalf <cmetcalf@xxxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: James Hogan <james.hogan@xxxxxxxxxx> Cc: Meredydd Luff <meredydd@xxxxxxxxxxxxxxx> Cc: David Drysdale <drysdale@xxxxxxxxxx> --- .../features/seccomp/seccomp-filter/arch-support.txt | 2 +- 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 +++++ 5 files changed, 25 insertions(+), 1 deletion(-) diff --git a/Documentation/features/seccomp/seccomp-filter/arch-support.txt b/Documentation/features/seccomp/seccomp-filter/arch-support.txt index 76d39d6..4f66ec1 100644 --- a/Documentation/features/seccomp/seccomp-filter/arch-support.txt +++ b/Documentation/features/seccomp/seccomp-filter/arch-support.txt @@ -33,7 +33,7 @@ | sh: | TODO | | sparc: | TODO | | tile: | ok | - | um: | TODO | + | um: | ok | | unicore32: | TODO | | x86: | ok | | xtensa: | TODO | diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common index d195a87..cc00134 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 28a9885..4b2ed58 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 53968aa..053baff 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 0d624e0..5abc677 100644 --- a/arch/um/kernel/skas/syscall.c +++ b/arch/um/kernel/skas/syscall.c @@ -5,6 +5,7 @@ #include <linux/kernel.h> #include <linux/ptrace.h> +#include <linux/seccomp.h> #include <kern_util.h> #include <sysdep/ptrace.h> #include <sysdep/ptrace_user.h> @@ -20,6 +21,10 @@ 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; -- 2.6.4 -- 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
