lkml.org 
[lkml]   [2020]   [May]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v5 3/6] fs: Enable to enforce noexec mounts or file exec through O_MAYEXEC
    On Thu, May 14, 2020 at 08:22:01AM -0400, Stephen Smalley wrote:
    > On Wed, May 13, 2020 at 11:05 PM Kees Cook <keescook@chromium.org> wrote:
    > >
    > > On Wed, May 13, 2020 at 04:27:39PM -0700, Kees Cook wrote:
    > > > Like, couldn't just the entire thing just be:
    > > >
    > > > diff --git a/fs/namei.c b/fs/namei.c
    > > > index a320371899cf..0ab18e19f5da 100644
    > > > --- a/fs/namei.c
    > > > +++ b/fs/namei.c
    > > > @@ -2849,6 +2849,13 @@ static int may_open(const struct path *path, int acc_mode, int flag)
    > > > break;
    > > > }
    > > >
    > > > + if (unlikely(mask & MAY_OPENEXEC)) {
    > > > + if (sysctl_omayexec_enforce & OMAYEXEC_ENFORCE_MOUNT &&
    > > > + path_noexec(path))
    > > > + return -EACCES;
    > > > + if (sysctl_omayexec_enforce & OMAYEXEC_ENFORCE_FILE)
    > > > + acc_mode |= MAY_EXEC;
    > > > + }
    > > > error = inode_permission(inode, MAY_OPEN | acc_mode);
    > > > if (error)
    > > > return error;
    > > >
    > >
    > > FYI, I've confirmed this now. Effectively with patch 2 dropped, patch 3
    > > reduced to this plus the Kconfig and sysctl changes, the self tests
    > > pass.
    > >
    > > I think this makes things much cleaner and correct.
    >
    > I think that covers inode-based security modules but not path-based
    > ones (they don't implement the inode_permission hook). For those, I
    > would tentatively guess that we need to make sure FMODE_EXEC is set on
    > the open file and then they need to check for that in their file_open
    > hooks.

    Does there need to be an FMODE_OPENEXEC, or is the presence of
    FMODE_OPEN with FMODE_EXEC sufficient?

    --
    Kees Cook

    \
     
     \ /
      Last update: 2020-05-14 16:42    [W:4.103 / U:0.440 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site