jffs2: return -ERANGE when xattr buffer is too small

When a file have multiple xattrs and the passed buffer is
smaller than the required size, jffs2_listxattr() should
return -ERANGE instead of continue, else Oops may occur
due to memory corruption.

Also remove the unnecessary check ("rc < 0"), because
xhandle->list(...) will not return an error number.

Spotted by generic/377 in xfstests-dev.

NB: The problem had been fixed by commit 764a5c6b1fa4 ("xattr
handlers: Simplify list operation") in v4.5-rc1, but the
modification in that commit may be too much because it modifies
all file-systems which implement xattr, so I create a single
patch for jffs2 to fix the problem.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/jffs2/xattr.c b/fs/jffs2/xattr.c
index 4c2c03663533dc2fbf1e0c24dc5b08dec6ea943f..8e1427762eeb8262c923ee27fdb3213464721054 100644 (file)
--- a/fs/jffs2/xattr.c
+++ b/fs/jffs2/xattr.c
@@ -1004,12 +1004,14 @@ ssize_t jffs2_listxattr(struct dentry *dentry, char *buffer, size_t size)
                        rc = xhandle->list(xhandle, dentry, buffer + len,
                                           size - len, xd->xname,
                                           xd->name_len);
+                       if (rc > size - len) {
+                               rc = -ERANGE;
+                               goto out;
+                       }
                } else {
                        rc = xhandle->list(xhandle, dentry, NULL, 0,
                                           xd->xname, xd->name_len);
                }
-               if (rc < 0)
-                       goto out;
                len += rc;
        }
        rc = len;