• Lee Schermerhorn's avatar
    hugetlbfs: handle empty options string · b4c07bce
    Lee Schermerhorn authored
    I was seeing a null pointer deref in fs/super.c:vfs_kern_mount().
    Some file system get_sb() handler was returning NULL mnt_sb with
    a non-negative return value.  I also noticed a "hugetlbfs: Bad
    mount option:" message in the log.
    Turns out that hugetlbfs_parse_options() was not checking for an
    empty option string after call to strsep().  On failure,
    hugetlbfs_parse_options() returns 1.  hugetlbfs_fill_super() just
    passed this return code back up the call stack where
    vfs_kern_mount() missed the error and proceeded with a NULL mnt_sb.
    Apparently introduced by patch:
    The problem was exposed by this line in my fstab:
    none        /huge       hugetlbfs   defaults    0 0
    It can also be demonstrated by invoking mount of hugetlbfs
    directly with no options or a bogus option.
    This patch:
    1) adds the check for empty option to hugetlbfs_parse_options(),
    2) enhances the error message to bracket any unrecognized
       option with quotes ,
    3) modifies hugetlbfs_parse_options() to return -EINVAL on any
       unrecognized option,
    4) adds a BUG_ON() to vfs_kern_mount() to catch any get_sb()
       handler that returns a NULL mnt->mnt_sb with a return value
       >= 0.
    Signed-off-by: default avatarLee Schermerhorn <lee.schermerhorn@hp.com>
    Acked-by: default avatarRandy Dunlap <randy.dunlap@oracle.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
super.c 22.1 KB