pid_t getvpid(pid_t pid, pid_t source, pid_t target); This syscall converts pid from one pid-ns into pid in another pid-ns: it takes @pid in namespace of @source task (zero for current) and returns related pid in namespace of @target task (zero for current too). If pid is unreachable from target pid-ns then it returns zero.
Such conversion is required for interaction between processes from different pid-namespaces. For example when system service talks with client from isolated container via socket about task in container: getvpid(pid, client_pid, 0) -> pid in our pid namespace getvpid(pid, 0, client_pid) -> pid in client pid namespace Also service can get pid of init task and match it with container: getvpid(1, client_pid, 0) -> pid of init task for client_pid Seems like gdb and strace could use this too for converting pids of newly forked tasks (IIRR they get pid from %rax) into pid from correct namespace for further interaction. As a bonus syscall getvpid can compare pid namespaces and test isolation without mounted procfs: getvpid(1, 0, pid) == 0 -> pid in our sub-pid-namespace getvpid(1, 0, pid) == 1 -> pid in our pid-namespace getvpid(1, pid1, pid2) == 0 -> pid1 isolated from pid2 getvpid(1, pid1, pid2) == 1 -> tasks are in one pid-namespace getvpid(1, pid1, pid2) > 1 -> pid1 is in sub-pidns of pid2 Signed-off-by: Konstantin Khlebnikov <khlebni...@yandex-team.ru> --- arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + include/linux/syscalls.h | 1 + kernel/pid.c | 36 ++++++++++++++++++++++++++++++++ 4 files changed, 39 insertions(+) diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index 7663c455b9f6..dadb55d42fc9 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -382,3 +382,4 @@ 373 i386 shutdown sys_shutdown 374 i386 userfaultfd sys_userfaultfd 375 i386 membarrier sys_membarrier +376 i386 getvpid sys_getvpid diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index 278842fdf1f6..0338f2eb3b7c 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -331,6 +331,7 @@ 322 64 execveat stub_execveat 323 common userfaultfd sys_userfaultfd 324 common membarrier sys_membarrier +325 common getvpid sys_getvpid # # x32-specific system call numbers start at 512 to avoid cache impact diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index a460e2ef2843..3405c30999e3 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -222,6 +222,7 @@ asmlinkage long sys_nanosleep(struct timespec __user *rqtp, struct timespec __us asmlinkage long sys_alarm(unsigned int seconds); asmlinkage long sys_getpid(void); asmlinkage long sys_getppid(void); +asmlinkage long sys_getvpid(pid_t pid, pid_t source, pid_t target); asmlinkage long sys_getuid(void); asmlinkage long sys_geteuid(void); asmlinkage long sys_getgid(void); diff --git a/kernel/pid.c b/kernel/pid.c index ca368793808e..caa676ff7364 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -567,6 +567,42 @@ struct pid *find_ge_pid(int nr, struct pid_namespace *ns) return pid; } +/** + * sys_getvpid - convert pid from one pid-namespace into pid from another + * + * @pid - pid of requested task + * @source - pid of task in source pid-namespace, zero for current + * @target - pid of task in target pid-namespace, zero for current + * + * Returns pid from target pid-ns or zero if pid is unreachable. + * Returns -ESRCH if some of pids are not found. + */ +SYSCALL_DEFINE3(getvpid, pid_t, pid, pid_t, source, pid_t, target) +{ +#ifdef CONFIG_PID_NS + struct pid_namespace *current_ns = task_active_pid_ns(current); + struct pid_namespace *source_ns = current_ns, *target_ns = current_ns; + struct pid *task_pid; + pid_t result = -ESRCH; + + rcu_read_lock(); + if (source) + source_ns = ns_of_pid(find_pid_ns(source, current_ns)); + if (target) + target_ns = ns_of_pid(find_pid_ns(target, current_ns)); + if (source_ns && target_ns) { + task_pid = find_pid_ns(pid, source_ns); + if (task_pid) + result = pid_nr_ns(task_pid, target_ns); + } + rcu_read_unlock(); + + return result; +#else + return pid; +#endif /* CONFIG_PID_NS */ +} + /* * The pid hash table is scaled according to the amount of memory in the * machine. From a minimum of 16 slots up to 4096 slots at one gigabyte or -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/