This patch series enables secure computing (system call filtering) on arm64, and contains related enhancements and bug fixes.
NOTE: This versions contain a workaround against possible BUG_ON() failure at audit_syscall_exit(), but doesn't contain an extra optimization, as I submitted for arm, of excluding syscall enter/exit tracing against invalid system calls due to an issue that I reported in: http://lists.infradead.org/pipermail/linux-arm-kernel/2014-October/292170.ht...
The code was tested on ARMv8 fast model with 64-bit/32-bit userspace using: * libseccomp v2.1.1 with modifications for arm64, especially its "live" tests: No.20, 21 and 24. * modified version of Kees' seccomp test for 'changing/skipping a syscall' and seccomp() system call * in-house tests for 'changing/skipping a system call' by tracing with ptrace(SETREGSET, NT_SYSTEM_CALL) (that is, not via seccomp filter)' with and without audit tracing.
Changes v8 -> v9: * removed a restriction on syscall(-1) by setting a default errno [2/6]
Changes v7 -> v8: * changed an interface of changing a syscall number from ptrace(SET_SYSCALL) to ptrace(SETREGSET, NT_ARM_SYSTEM_CALL) [1/6] * removed IS_SKILL_SYSCALL macro [2/6] * clarified comments in syscall_trace_enter() [2/6] * changed unsigned int to compat_uint_t in compat_siginfo._sigsys [5/6] * moved to a new calling interface of secure_computing(void) [6/6]
Changes v6 -> v7: * simplified the condition of checking for user-issued syscall(-1) at syscall_trace_enter() [2/6] * defines __NR_seccomp_sigreturn only if arch-specific def doesn't exist. As Kees suggests, this is necessary for x86 and others. [3/6] * removed "#ifdef __ARCH_SIGSYS" which is always true on arm64. [5/6] * changed to call syscall_trace_exit() even if secure_computing fails. [6/6] In v6, syscall_trace_enter() returns RET_SYSCALL_SKIP_TRACE (== -2) and skips syscall_trace_exit() to minimize the overhead, but this case can be easily confused with user-issued (and invalid) syscall(-2). Anyway, this is now a consistent behavior with arm and other archs.
Changes v5 -> v6: * rebased to v3.17-rc * changed the interface of changing/skipping a system call from re-writing x8 register [v5 1/3] to using dedicated PTRACE_SET_SYSCALL command [1/6, 2/6] Patch [1/6] contains a checkpatch error around a switch statement, but it won't be fixed as in compat_arch_ptrace(). * added a new system call, seccomp(), for compat task [4/6] * added SIGSYS siginfo for compat task [5/6] * changed to always execute audit exit tracing to avoid OOPs [2/6, 6/6]
Changes v4 -> v5: * rebased to v3.16-rc * add patch [1/3] to allow ptrace to change a system call (please note that this patch should be applied even without seccomp.)
Changes v3 -> v4: * removed the following patch and moved it to "arm64: prerequisites for audit and ftrace" patchset since it is required for audit and ftrace in case of !COMPAT, too. "arm64: is_compat_task is defined both in asm/compat.h and linux/compat.h"
Changes v2 -> v3: * removed unnecessary 'type cast' operations [2/3] * check for a return value (-1) of secure_computing() explicitly [2/3] * aligned with the patch, "arm64: split syscall_trace() into separate functions for enter/exit" [2/3] * changed default of CONFIG_SECCOMP to n [2/3]
Changes v1 -> v2: * added generic seccomp.h for arm64 to utilize it [1,2/3] * changed syscall_trace() to return more meaningful value (-EPERM) on seccomp failure case [2/3] * aligned with the change in "arm64: make a single hook to syscall_trace() for all syscall features" v2 [2/3] * removed is_compat_task() definition from compat.h [3/3]
AKASHI Takahiro (6): arm64: ptrace: add NT_ARM_SYSTEM_CALL regset arm64: ptrace: allow tracer to skip a system call asm-generic: add generic seccomp.h for secure computing mode 1 arm64: add seccomp syscall for compat task arm64: add SIGSYS siginfo for compat task arm64: add seccomp support
arch/arm64/Kconfig | 14 +++++++++++++ arch/arm64/include/asm/compat.h | 7 +++++++ arch/arm64/include/asm/seccomp.h | 25 +++++++++++++++++++++++ arch/arm64/include/asm/unistd.h | 3 +++ arch/arm64/include/asm/unistd32.h | 3 ++- arch/arm64/kernel/entry.S | 10 +++++++++- arch/arm64/kernel/ptrace.c | 40 +++++++++++++++++++++++++++++++++++++ arch/arm64/kernel/signal32.c | 6 ++++++ include/asm-generic/seccomp.h | 30 ++++++++++++++++++++++++++++ include/uapi/linux/elf.h | 1 + 10 files changed, 137 insertions(+), 2 deletions(-) create mode 100644 arch/arm64/include/asm/seccomp.h create mode 100644 include/asm-generic/seccomp.h