[patch 3/3] vfs: make d_path() consistent across mount operations (be285c71) · Commits · 戴 / test

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>

fs/dcache.c

+7 −5

Original line number	Diff line number	Diff line
		@@ -1782,6 +1782,7 @@ char __d_path(const struct path path, struct path *root,
		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 @@ char __d_path(const struct path path, struct path *root,
		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 @@ char __d_path(const struct path path, struct path *root,
		dentry = parent;
		}

		out:
		spin_unlock(&vfsmount_lock);
		return retval;

		global_root:
		@@ -1829,9 +1829,11 @@ global_root:
		goto Elong;
		root->mnt = vfsmnt;
		root->dentry = dentry;
		return retval;
		goto out;

		Elong:
		return ERR_PTR(-ENAMETOOLONG);
		retval = ERR_PTR(-ENAMETOOLONG);
		goto out;
		}

		/**

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