| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <20060824210303.9fe7e77a.kamezawa.hiroyu@jp.fujitsu.com>
Date: Thu, 24 Aug 2006 21:03:03 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: ebiederm@...ssion.com, kamezawa.hiroyu@...fujitsu.com,
Andrew Morton <akpm@...l.org>, saito.tadashi@...t.fujitsu.com,
ak@...e.de
Subject: [RFC][PATCH] ps command race fix take 3 [3/4] proc_pid_readdir()
For remembering 'what process should be read in the next time',
uses watch_head, dual direction pointer.
If a task which is pointed by file descriptor is removed,
that pointer is moved to the next task (see release_task()).
This will guarantee readdir() can traverse all task in the safe way.
Signed-Off-By: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
fs/proc/base.c | 113 +++++++++++++++++++++++++++------------------------------
1 files changed, 55 insertions(+), 58 deletions(-)
Index: linux-2.6.18-rc4/fs/proc/base.c
===================================================================
--- linux-2.6.18-rc4.orig/fs/proc/base.c
+++ linux-2.6.18-rc4/fs/proc/base.c
@@ -71,6 +71,8 @@
#include <linux/cpuset.h>
#include <linux/audit.h>
#include <linux/poll.h>
+#include <linux/watch_head.h>
+
#include "internal.h"
/* NOTE:
@@ -2140,70 +2142,48 @@ out_no_task:
return result;
}
-/*
- * Find the first tgid to return to user space.
- *
- * Usually this is just whatever follows &init_task, but if the users
- * buffer was too small to hold the full list or there was a seek into
- * the middle of the directory we have more work to do.
- *
- * In the case of a short read we start with find_task_by_pid.
- *
- * In the case of a seek we start with &init_task and walk nr
- * threads past it.
- */
-static struct task_struct *first_tgid(int tgid, unsigned int nr)
+/* caller must take rcu_read_lock() */
+static struct task_struct *first_alive_process(struct task_struct *pos)
{
- struct task_struct *pos;
- rcu_read_lock();
- if (tgid && nr) {
- pos = find_task_by_pid(tgid);
- if (pos && thread_group_leader(pos))
- goto found;
- }
- /* If nr exceeds the number of processes get out quickly */
- pos = NULL;
- if (nr && nr >= nr_processes())
- goto done;
-
- /* If we haven't found our starting place yet start with
- * the init_task and walk nr tasks forward.
- */
- for (pos = next_task(&init_task); nr > 0; --nr) {
+ while (!pid_alive(pos)) {
+ if (pos == &init_task)
+ break;
pos = next_task(pos);
- if (pos == &init_task) {
- pos = NULL;
- goto done;
- }
}
-found:
- get_task_struct(pos);
-done:
+ return (pos == &init_task)? NULL : pos;
+}
+
+static struct task_struct *next_tgid(struct task_struct *task)
+{
+ struct task_struct *pos;
+ rcu_read_lock();
+ pos = first_alive_process(next_task(task));
+ put_task_struct(task);
+ if (pos)
+ get_task_struct(pos);
rcu_read_unlock();
return pos;
}
-
/*
- * Find the next task in the task list.
- * Return NULL if we loop or there is any error.
- *
- * The reference to the input task_struct is released.
+ * return the first process pointer by head.
+ * if head points no where, returns next_alive_task(init_task)
+ * if head points to init_task, returns NULL.
*/
-static struct task_struct *next_tgid(struct task_struct *start)
+static struct task_struct *first_tgid(struct watch_head *head)
{
- struct task_struct *pos;
+ struct task_struct *pos = NULL;
rcu_read_lock();
- pos = start;
- if (pid_alive(start))
- pos = next_task(start);
- if (pid_alive(pos) && (pos != &init_task)) {
- get_task_struct(pos);
- goto done;
+ pos = wh_get_remove_pointer(head,struct task_struct,watch);
+ if (!pos) {
+ pos = first_alive_process(next_task(&init_task));
+ } else if (pos == &init_task) {
+ return NULL;
+ } else {
+ pos = first_alive_process(pos);
}
- pos = NULL;
-done:
+ if (pos)
+ get_task_struct(pos);
rcu_read_unlock();
- put_task_struct(start);
return pos;
}
@@ -2213,6 +2193,7 @@ int proc_pid_readdir(struct file * filp,
char buf[PROC_NUMBUF];
unsigned int nr = filp->f_pos - FIRST_PROCESS_ENTRY;
struct task_struct *task;
+ struct watch_head *head;
int tgid;
if (!nr) {
@@ -2227,9 +2208,13 @@ int proc_pid_readdir(struct file * filp,
/* f_version caches the tgid value that the last readdir call couldn't
* return. lseek aka telldir automagically resets f_version to 0.
*/
- tgid = filp->f_version;
- filp->f_version = 0;
- for (task = first_tgid(tgid, nr);
+ head = filp->private_data;
+ /* if we reached to the end of task_list once, head is invalidated */
+ if (is_wh_invalid(head))
+ return 0;
+
+ /* f_pos counts # of read tasks. for lseek() */
+ for (task = first_tgid(head);
task;
task = next_tgid(task), filp->f_pos++) {
int len;
@@ -2238,13 +2223,25 @@ int proc_pid_readdir(struct file * filp,
len = snprintf(buf, sizeof(buf), "%d", tgid);
ino = fake_ino(tgid, PROC_TGID_INO);
if (filldir(dirent, buf, len, filp->f_pos, ino, DT_DIR) < 0) {
- /* returning this tgid failed, save it as the first
- * pid for the next readir call */
- filp->f_version = tgid;
+ /* this task is failed to be returned. remember this */
+ struct task_struct *pos = task;
+ rcu_read_lock();
+ do {
+ pos = first_alive_process(pos);
+ if (pos && add_watcher(head, &pos->watch))
+ break;
+ if (pos)
+ pos = next_task(pos);
+ } while (pos && pos != &init_task);
+ rcu_read_unlock();
put_task_struct(task);
+ task = pos;
break;
}
}
+ /* reached to the end of task_list */
+ if (!task)
+ invalidate_wh(head);
return 0;
}
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists