[PATCH RFC v2] pidns: introduce syscall getvpid
From: Konstantin Khlebnikov <hidden>
Date: 2015-09-24 13:53:41
pid_t getvpid(pid_t pid, int source, int target); This syscall converts pid from source pid-namespace into pid in target pid-namespace. Namespaces are defined by file descriptors pointing to namespace entries in proc (/proc/[pid]/ns/pid). If source / target is negative then current pid namespace is used. If pid is negative then getvpid() returns pid of parent task for -pid. If pid is unreachable from target namespace then syscall returns zero. Errors: ESRCH task not found EBADF closed file descriptor EINVAL not pid-namespace file descriptor Examples: getvpid(pid, ns, -1) -> pid in our pid namespace getvpid(pid, -1, ns) -> pid in container getvpid(1, ns1, ns2) > 0 -> ns1 inside ns2 getvpid(1, ns1, ns2) == 0 -> ns1 outside ns2 getvpid(1, ns, -1) -> init task of pid-namespace getvpid(-1, ns, -1) -> task in parent pid-namespace getvpid(-pid, -1, -1) -> get ppid by pid Signed-off-by: Konstantin Khlebnikov <redacted> --- v2: * use namespace-fd as second/third argument * add -pid for getting parent pid * move code into kernel/sys.c next to getppid * drop ifdef CONFIG_PID_NS * add generic syscall --- arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + include/linux/syscalls.h | 1 + include/uapi/asm-generic/unistd.h | 4 ++ kernel/sys.c | 63 ++++++++++++++++++++++++++++++++ 5 files changed, 69 insertions(+), 1 deletion(-)
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..01ac603c8b5c 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, int source, int target); asmlinkage long sys_getuid(void); asmlinkage long sys_geteuid(void); asmlinkage long sys_getgid(void);
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 8da542a2874d..163df44b23cf 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h@@ -711,9 +711,11 @@ __SYSCALL(__NR_bpf, sys_bpf) __SC_COMP(__NR_execveat, sys_execveat, compat_sys_execveat) #define __NR_membarrier 282 __SYSCALL(__NR_membarrier, sys_membarrier) +#define __NR_getvpid 283 +__SYSCALL(__NR_getvpid, sys_getvpid) #undef __NR_syscalls -#define __NR_syscalls 283 +#define __NR_syscalls 284 /* * All syscalls below here should go away really,
diff --git a/kernel/sys.c b/kernel/sys.c
index fa2f2f671a5c..fbfe938dd9d7 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c@@ -46,6 +46,7 @@ #include <linux/syscalls.h> #include <linux/kprobes.h> #include <linux/user_namespace.h> +#include <linux/proc_ns.h> #include <linux/binfmts.h> #include <linux/sched.h>
@@ -855,6 +856,68 @@ SYSCALL_DEFINE0(getppid) return pid; } +SYSCALL_DEFINE3(getvpid, pid_t, pid, int, source, int, target) +{ + struct file *source_file = NULL, *target_file = NULL; + struct pid_namespace *source_ns, *target_ns; + struct pid *struct_pid; + struct ns_common *ns; + pid_t result; + + if (source >= 0) { + source_file = proc_ns_fget(source); + result = PTR_ERR(source_file); + if (IS_ERR(source_file)) + goto out; + ns = get_proc_ns(file_inode(source_file)); + result = -EINVAL; + if (ns->ops->type != CLONE_NEWPID) + goto out; + source_ns = container_of(ns, struct pid_namespace, ns); + } else + source_ns = task_active_pid_ns(current); + + if (target >= 0) { + target_file = proc_ns_fget(target); + result = PTR_ERR(target_file); + if (IS_ERR(target_file)) + goto out; + ns = get_proc_ns(file_inode(target_file)); + result = -EINVAL; + if (ns->ops->type != CLONE_NEWPID) + goto out; + target_ns = container_of(ns, struct pid_namespace, ns); + } else + target_ns = task_active_pid_ns(current); + + rcu_read_lock(); + struct_pid = find_pid_ns(abs(pid), source_ns); + + if (struct_pid && pid < 0) { + struct task_struct *task; + + task = pid_task(struct_pid, PIDTYPE_PID); + if (task) + task = rcu_dereference(task->real_parent); + struct_pid = task ? task_pid(task) : NULL; + } + + if (struct_pid) + result = pid_nr_ns(struct_pid, target_ns); + else + result = -ESRCH; + rcu_read_unlock(); + +out: + if (!IS_ERR_OR_NULL(target_file)) + fput(target_file); + + if (!IS_ERR_OR_NULL(source_file)) + fput(source_file); + + return result; +} + SYSCALL_DEFINE0(getuid) { /* Only we change this so SMP safe */