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Message-ID: <4C20D1AE.5000205@ring3k.org>
Date: Wed, 23 Jun 2010 00:07:26 +0900
From: Mike McCormack <mikem@...g3k.org>
To: akpm@...ux-foundation.org
CC: oleg@...hat.com, kosaki.motohiro@...fujitsu.com, serue@...ibm.com,
jmorris@...ei.org, linux-kernel@...r.kernel.org
Subject: [PATCH] proc: Add complete process group list
If a process is in more than NGROUPS_SMALL (32) groups, it's not possible
for any other user space process to determine the list of groups it is
in using /proc/<pid>/status.
Increasing the list of groups listed by /proc/<pid>/status would lead to
very long lines that file, and possible misbehavior of userspace programs
that parse /proc/<pid>/status, so instead I have opted to create a new
file /proc/<pid>/groups, which contains the list of supplementary groups
for each pid.
The new file /proc/<pid>/groups consists of a single group id per line,
with each line being 11 characters long. This should be enough space
for 16bit or 32bit group ids.
This feature might be useful for a server listening on a unix domain pipe
to determine the list of groups that a client process is in from its pid.
Signed-off-by: Mike McCormack <mikem@...g3k.org>
---
fs/proc/base.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 55 insertions(+), 0 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index acb7ef8..689362c 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -82,6 +82,8 @@
#include <linux/pid_namespace.h>
#include <linux/fs_struct.h>
#include <linux/slab.h>
+#include <linux/cred.h>
+
#include "internal.h"
/* NOTE:
@@ -1325,6 +1327,57 @@ static const struct file_operations proc_pid_set_comm_operations = {
.release = single_release,
};
+/* supplementary groups, one per line */
+static int groups_proc_show(struct seq_file *m, void *v)
+{
+ struct inode *inode = m->private;
+ struct group_info *group_info;
+ struct task_struct *task;
+ const struct cred *cred;
+ struct pid *pid;
+ unsigned int g;
+
+ pid = proc_pid(inode);
+ task = get_pid_task(pid, PIDTYPE_PID);
+ if (!task)
+ return -ESRCH;
+
+ cred = get_task_cred(task);
+ group_info = cred->group_info;
+
+ /*
+ * Groups may be 16bit or 32bit.
+ * Try to be easily machine and human readable.
+ */
+ for (g = 0; g < group_info->ngroups; g++)
+ seq_printf(m, "%-10u\n", GROUP_AT(group_info, g));
+
+ put_cred(cred);
+ put_task_struct(task);
+
+ return 0;
+}
+
+static int groups_proc_open(struct inode *inode, struct file *filp)
+{
+ int ret;
+
+ ret = single_open(filp, groups_proc_show, NULL);
+ if (!ret) {
+ struct seq_file *m = filp->private_data;
+
+ m->private = inode;
+ }
+ return ret;
+}
+
+static const struct file_operations proc_groups_operations = {
+ .open = groups_proc_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
/*
* We added or removed a vma mapping the executable. The vmas are only mapped
* during exec and are not mapped with the mmap system call.
@@ -2586,6 +2639,7 @@ static const struct pid_entry tgid_base_stuff[] = {
INF("cmdline", S_IRUGO, proc_pid_cmdline),
ONE("stat", S_IRUGO, proc_tgid_stat),
ONE("statm", S_IRUGO, proc_pid_statm),
+ REG("groups", S_IRUSR, proc_groups_operations),
REG("maps", S_IRUGO, proc_maps_operations),
#ifdef CONFIG_NUMA
REG("numa_maps", S_IRUGO, proc_numa_maps_operations),
@@ -2921,6 +2975,7 @@ static const struct pid_entry tid_base_stuff[] = {
INF("cmdline", S_IRUGO, proc_pid_cmdline),
ONE("stat", S_IRUGO, proc_tid_stat),
ONE("statm", S_IRUGO, proc_pid_statm),
+ REG("groups", S_IRUSR, proc_groups_operations),
REG("maps", S_IRUGO, proc_maps_operations),
#ifdef CONFIG_NUMA
REG("numa_maps", S_IRUGO, proc_numa_maps_operations),
--
1.5.6.5
--
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