From: Eric W. Biederman <ebiederm@xmission.com>
Date: Tue, 31 Jan 2012 05:24:59 +0000 (-0800)
Subject: sysctl: Don't call sysctl_follow_link unless we are a link.
X-Git-Tag: firefly_0821_release~3680^2~3260^2~1
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4e75732035d7e97e001bdf6e3149d3967c0221de;p=firefly-linux-kernel-4.4.55.git

sysctl: Don't call sysctl_follow_link unless we are a link.

There are no functional changes.  Just code motion to make it
clear that we don't follow a link between sysctl roots unless the
directory entry actually is a link.

Suggested-by:  Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index e5601dc24088..a7708b7c957f 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -451,10 +451,12 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
 	if (!p)
 		goto out;
 
-	ret = sysctl_follow_link(&h, &p, current->nsproxy);
-	err = ERR_PTR(ret);
-	if (ret)
-		goto out;
+	if (S_ISLNK(p->mode)) {
+		ret = sysctl_follow_link(&h, &p, current->nsproxy);
+		err = ERR_PTR(ret);
+		if (ret)
+			goto out;
+	}
 
 	err = ERR_PTR(-ENOMEM);
 	inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
@@ -601,10 +603,12 @@ static int proc_sys_link_fill_cache(struct file *filp, void *dirent,
 	int err, ret = 0;
 	head = sysctl_head_grab(head);
 
-	/* It is not an error if we can not follow the link ignore it */
-	err = sysctl_follow_link(&head, &table, current->nsproxy);
-	if (err)
-		goto out;
+	if (S_ISLNK(table->mode)) {
+		/* It is not an error if we can not follow the link ignore it */
+		err = sysctl_follow_link(&head, &table, current->nsproxy);
+		if (err)
+			goto out;
+	}
 
 	ret = proc_sys_fill_cache(filp, dirent, filldir, head, table);
 out:
@@ -950,10 +954,6 @@ static int sysctl_follow_link(struct ctl_table_header **phead,
 	struct ctl_dir *dir;
 	int ret;
 
-	/* Get out quickly if not a link */
-	if (!S_ISLNK((*pentry)->mode))
-		return 0;
-
 	ret = 0;
 	spin_lock(&sysctl_lock);
 	root = (*pentry)->data;