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Biederman" , Andrew Morton , Andy Lutomirski , "Michael Kerrisk (man-pages)" References: <152788068212.768348.15192457501079586650.stgit@buzz> From: Nagarathnam Muthusamy Message-ID: <6dcb9f67-03dc-fa58-4690-fe69b23ada23@oracle.com> Date: Tue, 12 Jun 2018 10:08:28 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <152788068212.768348.15192457501079586650.stgit@buzz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8921 signatures=668702 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=45 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1805220000 definitions=main-1806120192 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/01/2018 12:18 PM, Konstantin Khlebnikov wrote: > Each process have different pids, one for each pid namespace it belongs. > When interaction happens within single pid-ns translation isn't required. > More complicated scenarios needs special handling. > > For example: > - reading pid-files or logs written inside container with pid namespace > - writing logs with internal pids outside container for pushing them into > - attaching with ptrace to tasks from different pid namespace > > Generally speaking, any cross pid-ns API with pids needs translation. > > Currently there are several interfaces that could be used here: > > Pid namespaces are identified by device and inode of /proc/[pid]/ns/pid. > > Pids for nested pid namespaces are shown in file /proc/[pid]/status. > In some cases pid translation could be easily done using this information. > Backward translation requires scanning all tasks and becomes really > complicated for deeper namespace nesting. > > Unix socket automatically translates pid attached to SCM_CREDENTIALS. > This requires CAP_SYS_ADMIN for sending arbitrary pids and entering > into pid namespace, this expose process and could be insecure. > > This patch adds new syscall for converting pids between pid namespaces: > > pid_t translate_pid(pid_t pid, int source, int target); > > Pid-namespaces are referred file descriptors opened to proc files > /proc/[pid]/ns/pid or /proc/[pid]/ns/pid_for_children. > Negative argument points to current pid namespace. > > Syscall returns pid in target pid-ns or zero if task have no pid there. > > Error codes: > EBADF - file descriptor is closed > EINVAL - file descriptor isn't pid namespace > ESRCH - task not found in @source namespace > > Translation could breach pid-ns isolation and return pids from outer pid > namespaces iff process already has file descriptor for these namespaces. > > Examples: > translate_pid(pid, ns, -1) - get pid in our pid namespace > translate_pid(pid, -1, ns) - get pid in other pid namespace > translate_pid(1, ns, -1) - get pid of init task for namespace > translate_pid(pid, -1, ns) > 0 - is pid is reachable from ns? > translate_pid(1, ns1, ns2) > 0 - is ns1 inside ns2? > translate_pid(1, ns1, ns2) == 0 - is ns1 outside ns2? > translate_pid(1, ns1, ns2) == 1 - is ns1 equal ns2? > > Signed-off-by: Konstantin Khlebnikov > Reanimated-by: Nagarathnam Muthusamy > > --- > > v1: https://lkml.org/lkml/2015/9/15/411 > v2: https://lkml.org/lkml/2015/9/24/278 > * 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 > v3: https://lkml.org/lkml/2015/9/28/3 > * use proc_ns_fdget() > * update description > * rebase to next-20150925 > * fix conflict with mlock2 > v4: https://lkml.org/lkml/2017/10/13/177 > * rename from getvpid() into translate_pid() > * remove syscall if CONFIG_PID_NS=n > * drop -pid for parent task > * drop fget-fdget optimizations > * add helper get_pid_ns_by_fd() > * wire only into x86 > v5: https://lkml.org/lkml/2018/4/4/677 > * rewrite commit message > * resolve pidns by task pid or by pidns fd > * add arguments source_type and target_type > v6: > * revert back minimized v4 design > * rebase to next-20180601 > * fix COND_SYSCALL stub > * use next syscall number, old used for io_pgetevents > > --- sample tool --- > > #define _GNU_SOURCE > #include > #include > #include > #include > #include > #include > #include > > #ifndef SYS_translate_pid > #ifdef __x86_64__ > #define SYS_translate_pid 334 > #elif defined __i386__ > #define SYS_translate_pid 386 > #endif > #endif > > pid_t translate_pid(pid_t pid, int source, int target) { > return syscall(SYS_translate_pid, pid, source, target); > } > > int main(int argc, char **argv) { > int pid, source, target; > char buf[64]; > > if (argc != 4) > errx(1, "usage: %s ", argv[0]); > > pid = atoi(argv[1]); > source = atoi(argv[2]); > target = atoi(argv[3]); > > if (source > 0) { > snprintf(buf, sizeof(buf), "/proc/%d/ns/pid", source); > source = open(buf, O_RDONLY); > if (source < 0) > err(2, "open source %s", buf); > } > > if (target > 0) { > snprintf(buf, sizeof(buf), "/proc/%d/ns/pid", target); > target = open(buf, O_RDONLY); > if (target < 0) > err(2, "open target %s", buf); > } > > pid = translate_pid(pid, source, target); > if (pid < 0) > err(2, "translate_pid"); > > printf("%d\n", pid); > return 0; > } > > --- > --- > arch/x86/entry/syscalls/syscall_32.tbl | 1 > arch/x86/entry/syscalls/syscall_64.tbl | 1 > include/linux/syscalls.h | 1 > kernel/pid_namespace.c | 66 ++++++++++++++++++++++++++++++++ > kernel/sys_ni.c | 3 + > 5 files changed, 72 insertions(+) > > diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl > index 14a2f996e543..e70685750d43 100644 > --- a/arch/x86/entry/syscalls/syscall_32.tbl > +++ b/arch/x86/entry/syscalls/syscall_32.tbl > @@ -397,3 +397,4 @@ > 383 i386 statx sys_statx __ia32_sys_statx > 384 i386 arch_prctl sys_arch_prctl __ia32_compat_sys_arch_prctl > 385 i386 io_pgetevents sys_io_pgetevents __ia32_compat_sys_io_pgetevents > +386 i386 translate_pid sys_translate_pid __ia32_sys_translate_pid > diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl > index cd36232ab62f..ebfd89055424 100644 > --- a/arch/x86/entry/syscalls/syscall_64.tbl > +++ b/arch/x86/entry/syscalls/syscall_64.tbl > @@ -342,6 +342,7 @@ > 331 common pkey_free __x64_sys_pkey_free > 332 common statx __x64_sys_statx > 333 common io_pgetevents __x64_sys_io_pgetevents > +334 common translate_pid __x64_sys_translate_pid Looks like the syscall numbers used here were claimed by "resq" in the linux-next tree. Thanks, Nagarathnam. > > # > # 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 390e814fdc8d..3f33971cf1c8 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -843,6 +843,7 @@ asmlinkage long sys_clock_adjtime(clockid_t which_clock, > struct timex __user *tx); > asmlinkage long sys_syncfs(int fd); > asmlinkage long sys_setns(int fd, int nstype); > +asmlinkage long sys_translate_pid(pid_t pid, int source, int target); > asmlinkage long sys_sendmmsg(int fd, struct mmsghdr __user *msg, > unsigned int vlen, unsigned flags); > asmlinkage long sys_process_vm_readv(pid_t pid, > diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c > index 2a2ac53d8b8b..3b872cbbe264 100644 > --- a/kernel/pid_namespace.c > +++ b/kernel/pid_namespace.c > @@ -13,6 +13,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -380,6 +381,71 @@ static void pidns_put(struct ns_common *ns) > put_pid_ns(to_pid_ns(ns)); > } > > +static struct pid_namespace *get_pid_ns_by_fd(int fd) > +{ > + struct pid_namespace *pidns; > + struct ns_common *ns; > + struct file *file; > + > + file = proc_ns_fget(fd); > + if (IS_ERR(file)) > + return ERR_CAST(file); > + > + ns = get_proc_ns(file_inode(file)); > + if (ns->ops->type == CLONE_NEWPID) > + pidns = get_pid_ns(to_pid_ns(ns)); > + else > + pidns = ERR_PTR(-EINVAL); > + > + fput(file); > + return pidns; > +} > + > +/* > + * translate_pid - convert pid in source pid-ns into target pid-ns. > + * @pid: pid for translation > + * @source: pid-ns file descriptor or -1 for active namespace > + * @target: pid-ns file descriptor or -1 for active namesapce > + * > + * Returns pid in @target pid-ns, zero if task have no pid there, > + * or -ESRCH if task with @pid does not found in @source pid-ns. > + */ > +SYSCALL_DEFINE3(translate_pid, pid_t, pid, int, source, int, target) > +{ > + struct pid_namespace *source_ns, *target_ns; > + struct pid *struct_pid; > + pid_t result; > + > + if (source >= 0) { > + source_ns = get_pid_ns_by_fd(source); > + result = PTR_ERR(source_ns); > + if (IS_ERR(source_ns)) > + goto err_source; > + } else > + source_ns = task_active_pid_ns(current); > + > + if (target >= 0) { > + target_ns = get_pid_ns_by_fd(target); > + result = PTR_ERR(target_ns); > + if (IS_ERR(target_ns)) > + goto err_target; > + } else > + target_ns = task_active_pid_ns(current); > + > + rcu_read_lock(); > + struct_pid = find_pid_ns(pid, source_ns); > + result = struct_pid ? pid_nr_ns(struct_pid, target_ns) : -ESRCH; > + rcu_read_unlock(); > + > + if (target >= 0) > + put_pid_ns(target_ns); > +err_target: > + if (source >= 0) > + put_pid_ns(source_ns); > +err_source: > + return result; > +} > + > static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns) > { > struct pid_namespace *active = task_active_pid_ns(current); > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c > index 06b4ccee0047..bf276e9ace9a 100644 > --- a/kernel/sys_ni.c > +++ b/kernel/sys_ni.c > @@ -153,6 +153,9 @@ COND_SYSCALL_COMPAT(kexec_load); > COND_SYSCALL(init_module); > COND_SYSCALL(delete_module); > > +/* kernel/pid_namespace.c */ > +COND_SYSCALL(translate_pid); > + > /* kernel/posix-timers.c */ > > /* kernel/printk.c */ >