From: Miklos Szeredi <mszeredi@redhat.com>
Date: Sat, 1 Oct 2016 05:32:32 +0000 (+0200)
Subject: fuse: listxattr: verify xattr list
X-Git-Tag: firefly_0821_release~176^2~4^2~23^2~22
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=80b742b84f85e3688e02eefd8b820642c4635329;p=firefly-linux-kernel-4.4.55.git

fuse: listxattr: verify xattr list

commit cb3ae6d25a5471be62bfe6ac1fccc0e91edeaba0 upstream.

Make sure userspace filesystem is returning a well formed list of xattr
names (zero or more nonzero length, null terminated strings).

[Michael Theall: only verify in the nonzero size case]

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 5e2e08712d3b..67c0d1046c61 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1797,6 +1797,23 @@ static ssize_t fuse_getxattr(struct dentry *entry, const char *name,
 	return ret;
 }
 
+static int fuse_verify_xattr_list(char *list, size_t size)
+{
+	size_t origsize = size;
+
+	while (size) {
+		size_t thislen = strnlen(list, size);
+
+		if (!thislen || thislen == size)
+			return -EIO;
+
+		size -= thislen + 1;
+		list += thislen + 1;
+	}
+
+	return origsize;
+}
+
 static ssize_t fuse_listxattr(struct dentry *entry, char *list, size_t size)
 {
 	struct inode *inode = d_inode(entry);
@@ -1832,6 +1849,8 @@ static ssize_t fuse_listxattr(struct dentry *entry, char *list, size_t size)
 	ret = fuse_simple_request(fc, &args);
 	if (!ret && !size)
 		ret = outarg.size;
+	if (ret > 0 && size)
+		ret = fuse_verify_xattr_list(list, ret);
 	if (ret == -ENOSYS) {
 		fc->no_listxattr = 1;
 		ret = -EOPNOTSUPP;