linux-kernel - [PATCH 1/1] proc: make /proc/self point to thread

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Message-ID: <20130827144004.GB19425@redhat.com>
Date:	Tue, 27 Aug 2013 16:40:04 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Willy Tarreau <w@....eu>, Al Viro <viro@...iv.linux.org.uk>,
	Andy Lutomirski <luto@...capital.net>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	Brad Spengler <spender@...ecurity.net>
Subject: [PATCH 1/1] proc: make /proc/self point to thread

/proc/self points to /proc/<tgid>, not to /proc/<tid>, and thus
"self" actually means "group leader".

Change fs/proc/self.c to print the caller's tid, this is probably
what the users actually expect.

Note: this is obviously semantically different and the difference
is subtle, but most (all?) users should not notice this change.
Lets see if it breaks something.

Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 fs/proc/self.c |   14 +++++++-------
 1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/fs/proc/self.c b/fs/proc/self.c
index 6b6a993..7da7154 100644
--- a/fs/proc/self.c
+++ b/fs/proc/self.c
@@ -11,26 +11,26 @@ 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 tid = task_pid_nr_ns(current, ns);
 	char tmp[PROC_NUMBUF];
-	if (!tgid)
+	if (!tid)
 		return -ENOENT;
-	sprintf(tmp, "%d", tgid);
+	sprintf(tmp, "%d", tid);
 	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 tid = task_pid_nr_ns(current, ns);
 	char *name = ERR_PTR(-ENOENT);
-	if (tgid) {
+	if (tid) {
 		/* 11 for max length of signed int in decimal + NULL term */
 		name = kmalloc(12, GFP_KERNEL);
 		if (!name)
 			name = ERR_PTR(-ENOMEM);
 		else
-			sprintf(name, "%d", tgid);
+			sprintf(name, "%d", tid);
 	}
 	nd_set_link(nd, name);
 	return NULL;
@@ -57,7 +57,7 @@ int proc_setup_self(struct super_block *s)
 	struct inode *root_inode = s->s_root->d_inode;
 	struct pid_namespace *ns = s->s_fs_info;
 	struct dentry *self;
-	
+
 	mutex_lock(&root_inode->i_mutex);
 	self = d_alloc_name(s->s_root, "self");
 	if (self) {
-- 
1.5.5.1


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