linux-kernel - [PATCH] proc: Fix the threaded /proc/self.

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Message-ID: <m1k5ocr14n.fsf_-_@ebiederm.dsl.xmission.com>
Date:	Tue, 20 Nov 2007 15:41:12 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Pavel Emelyanov <xemul@...nvz.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Pavel Machek <pavel@....cz>,
	kernel list <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: [PATCH] proc: Fix the threaded /proc/self.


Long ago when the CLONE_THREAD support first went it someone
thought it would be wise to point /proc/self at /proc/<tgid>
instead of /proc/<pid>.

Given that /proc/<tgid> can return information about a very different
task (if enough things have been unshared) then our current process
/proc/<tgid> seems blatantly wrong.  So far I have yet to think up
an example where the current behavior would be advantageous, and
I can see several places where it is seriously non-intuitive.

We may be stuck with the current broken behavior for backwards
compatibility reasons but lets try fixing our ancient bug for the
2.6.25 time frame and see if anyone screams.

Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
---
 fs/proc/base.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 34a1821..8502436 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2050,22 +2050,22 @@ static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
 			      int buflen)
 {
 	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
-	pid_t tgid = task_tgid_nr_ns(current, ns);
+	pid_t pid = task_pid_nr_ns(current, ns);
 	char tmp[PROC_NUMBUF];
-	if (!tgid)
+	if (!pid)
 		return -ENOENT;
-	sprintf(tmp, "%d", tgid);
+	sprintf(tmp, "%d", pid);
 	return vfs_readlink(dentry,buffer,buflen,tmp);
 }
 
 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
 	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
-	pid_t tgid = task_tgid_nr_ns(current, ns);
+	pid_t pid = task_pid_nr_ns(current, ns);
 	char tmp[PROC_NUMBUF];
-	if (!tgid)
+	if (!pid)
 		return ERR_PTR(-ENOENT);
-	sprintf(tmp, "%d", task_tgid_nr_ns(current, ns));
+	sprintf(tmp, "%d", pid);
 	return ERR_PTR(vfs_follow_link(nd,tmp));
 }
 
-- 
1.5.3.rc6.17.g1911

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