staging: erofs: refuse to mount images with malformed volume name

As Richard reminder [1], A valid volume name should be
ended in NIL terminator within the length of volume_name.

Since this field currently isn't really used, let's fix
it to avoid potential bugs in the future.

[1] https://lore.kernel.org/r/1133002215.69049.1566119033047.JavaMail.zimbra@nod.at/

Reported-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190818102824.22330-1-hsiangkao@aol.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/erofs/super.c b/drivers/staging/erofs/super.c
index f65a1ff..2da4710 100644 (file)
--- a/drivers/staging/erofs/super.c
+++ b/drivers/staging/erofs/super.c
@@ -131,9 +131,14 @@ static int superblock_read(struct super_block *sb)
        sbi->build_time_nsec = le32_to_cpu(layout->build_time_nsec);
 
        memcpy(&sb->s_uuid, layout->uuid, sizeof(layout->uuid));
-       memcpy(sbi->volume_name, layout->volume_name,
-              sizeof(layout->volume_name));
 
+       ret = strscpy(sbi->volume_name, layout->volume_name,
+                     sizeof(layout->volume_name));
+       if (ret < 0) {  /* -E2BIG */
+               errln("bad volume name without NIL terminator");
+               ret = -EFSCORRUPTED;
+               goto out;
+       }
        ret = 0;
 out:
        brelse(bh);