Add a file called pidnr under /proc/task/. Reading this file gives the
pid of /proc/task in the reading task's namespace (or 0 if there is no
valid pid).
This fills a need currently not solvable at all. The particular need I
have for it is so that a task inside a container can pass requests to a
task outside the container (using an open fd for /proc/task) to have the
target task moved to a new cgroup. Others have asked for this ability
for other reasons.
Signed-off-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
Cc: containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Cc: Stéphane Graber <stgraber@xxxxxxxxxx>
---
fs/proc/base.c | 25 ++++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index c3834da..b7499eb 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -899,6 +899,28 @@ static const struct file_operations proc_environ_operations = {
.release = mem_release,
};
+#define TMPBUFLEN 21
+static ssize_t pidnr_read(struct file * file, char __user * buf,
+ size_t count, loff_t *ppos)
+{
+ struct inode * inode = file_inode(file);
+ struct task_struct *task = get_proc_task(inode);
+ ssize_t length;
+ char tmpbuf[TMPBUFLEN];
+
+ if (!task)
+ return -ESRCH;
+ length = scnprintf(tmpbuf, TMPBUFLEN, "%u\n",
+ task_pid_vnr(task));
+ put_task_struct(task);
+ return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
+}
+
+static const struct file_operations pidnr_operations = {
+ .read = pidnr_read,
+ .llseek = generic_file_llseek,
+};
+
static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count,
loff_t *ppos)
{
@@ -1096,7 +1118,6 @@ static const struct file_operations proc_oom_score_adj_operations = {
};
#ifdef CONFIG_AUDITSYSCALL
-#define TMPBUFLEN 21
static ssize_t proc_loginuid_read(struct file * file, char __user * buf,
size_t count, loff_t *ppos)
{
@@ -2642,6 +2663,7 @@ static const struct pid_entry tgid_base_stuff[] = {
DIR("net", S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations),
#endif
REG("environ", S_IRUSR, proc_environ_operations),
+ REG("pidnr", S_IRUGO, pidnr_operations),
INF("auxv", S_IRUSR, proc_pid_auxv),
ONE("status", S_IRUGO, proc_pid_status),
ONE("personality", S_IRUGO, proc_pid_personality),
@@ -2999,6 +3021,7 @@ static const struct pid_entry tid_base_stuff[] = {
DIR("fdinfo", S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations),
DIR("ns", S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations),
REG("environ", S_IRUSR, proc_environ_operations),
+ REG("pidnr", S_IRUGO, pidnr_operations),
INF("auxv", S_IRUSR, proc_pid_auxv),
ONE("status", S_IRUGO, proc_pid_status),
ONE("personality", S_IRUGO, proc_pid_personality),
--
1.7.9.5
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