[patch 3/3] vfs: make d_path() consistent across mount operations

The path that __d_path() computes can become slightly inconsistent when it races with mount operations: it grabs the vfsmount_lock when traversing mount points but immediately drops it again, only to re-grab it when it reaches the next mount point. The result is that the filename computed is not always consisent, and the file may never have had that name. (This is unlikely, but still possible.) Fix this by grabbing the vfsmount_lock for the whole duration of __d_path(). Signed-off-by: Andreas Gruenbacher <agruen@suse.de> Signed-off-by: John Johansen <jjohansen@suse.de> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Acked-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

[patch 3/3] vfs: make d_path() consistent across mount operations
The path that __d_path() computes can become slightly inconsistent when it races with mount operations: it grabs the vfsmount_lock when traversing mount points but immediately drops it again, only to re-grab it when it reaches the next mount point. The result is that the filename computed is not always consisent, and the file may never have had that name. (This is unlikely, but still possible.) Fix this by grabbing the vfsmount_lock for the whole duration of __d_path(). Signed-off-by: Andreas Gruenbacher <agruen@suse.de> Signed-off-by: John Johansen <jjohansen@suse.de> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Acked-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Andreas Gruenbacher · Al Viro
1 parent f9f48ec72b
Showing 1 changed file with 7 additions and 5 deletions Side-by-side Diff
fs/dcache.c
@@ -1782,6 +1782,7 @@
 	char * end = buffer+buflen;
 	char * retval;
  
+	spin_lock(&vfsmount_lock);
 	prepend(&end, &buflen, "\0", 1);
 	if (!IS_ROOT(dentry) && d_unhashed(dentry) &&
 		(prepend(&end, &buflen, " (deleted)", 10) != 0))
  
  
@@ -1800,14 +1801,11 @@
 			break;
 		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
 			/* Global root? */
-			spin_lock(&vfsmount_lock);
 			if (vfsmnt->mnt_parent == vfsmnt) {
-				spin_unlock(&vfsmount_lock);
 				goto global_root;
 			}
 			dentry = vfsmnt->mnt_mountpoint;
 			vfsmnt = vfsmnt->mnt_parent;
-			spin_unlock(&vfsmount_lock);
 			continue;
 		}
 		parent = dentry->d_parent;
@@ -1820,6 +1818,8 @@
 		dentry = parent;
 	}
  
+out:
+	spin_unlock(&vfsmount_lock);
 	return retval;
  
 global_root:
  
@@ -1829,9 +1829,11 @@
 		goto Elong;
 	root->mnt = vfsmnt;
 	root->dentry = dentry;
-	return retval;
+	goto out;
+
 Elong:
-	return ERR_PTR(-ENAMETOOLONG);
+	retval = ERR_PTR(-ENAMETOOLONG);
+	goto out;
 }
  
 /**
...	...	@@ -1782,6 +1782,7 @@
1782	1782	char * end = buffer+buflen;
1783	1783	char * retval;
1784	1784
	1785	+ spin_lock(&vfsmount_lock);
1785	1786	prepend(&end, &buflen, "\0", 1);
1786	1787	if (!IS_ROOT(dentry) && d_unhashed(dentry) &&
1787	1788	(prepend(&end, &buflen, " (deleted)", 10) != 0))
1788	1789
1789	1790
...	...	@@ -1800,14 +1801,11 @@
1800	1801	break;
1801	1802	if (dentry == vfsmnt->mnt_root \|\| IS_ROOT(dentry)) {
1802	1803	/* Global root? */
1803		- spin_lock(&vfsmount_lock);
1804	1804	if (vfsmnt->mnt_parent == vfsmnt) {
1805		- spin_unlock(&vfsmount_lock);
1806	1805	goto global_root;
1807	1806	}
1808	1807	dentry = vfsmnt->mnt_mountpoint;
1809	1808	vfsmnt = vfsmnt->mnt_parent;
1810		- spin_unlock(&vfsmount_lock);
1811	1809	continue;
1812	1810	}
1813	1811	parent = dentry->d_parent;
...	...	@@ -1820,6 +1818,8 @@
1820	1818	dentry = parent;
1821	1819	}
1822	1820
	1821	+out:
	1822	+ spin_unlock(&vfsmount_lock);
1823	1823	return retval;
1824	1824
1825	1825	global_root:
1826	1826
...	...	@@ -1829,9 +1829,11 @@
1829	1829	goto Elong;
1830	1830	root->mnt = vfsmnt;
1831	1831	root->dentry = dentry;
1832		- return retval;
	1832	+ goto out;
	1833	+
1833	1834	Elong:
1834		- return ERR_PTR(-ENAMETOOLONG);
	1835	+ retval = ERR_PTR(-ENAMETOOLONG);
	1836	+ goto out;
1835	1837	}
1836	1838
1837	1839	/**