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    SubjectRe: [PATCH 2/3] Make static usermode helper binaries constant
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    On Tue, 2017-01-17 at 16:56 +0100, Greg KH wrote:
    > On Tue, Jan 17, 2017 at 10:45:45AM -0500, Jeff Layton wrote:
    > > On Mon, 2017-01-16 at 17:50 +0100, Greg KH wrote:
    > > > From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    > > >
    > > > There are a number of usermode helper binaries that are "hard coded" in
    > > > the kernel today, so mark them as "const" to make it harder for someone
    > > > to change where the variables point to.
    > > >
    > > > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    > > > Cc: Thomas Sailer <t.sailer@alumni.ethz.ch>
    > > > Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
    > > > Cc: Johan Hovold <johan@kernel.org>
    > > > Cc: Alex Elder <elder@kernel.org>
    > > > Cc: "J. Bruce Fields" <bfields@fieldses.org>
    > > > Cc: Jeff Layton <jlayton@poochiereds.net>
    > > > Cc: David Howells <dhowells@redhat.com>
    > > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    >
    >
    >
    > > > --- a/fs/nfsd/nfs4layouts.c
    > > > +++ b/fs/nfsd/nfs4layouts.c
    > > > @@ -613,6 +613,7 @@ nfsd4_cb_layout_fail(struct nfs4_layout_stateid *ls)
    > > > {
    > > > struct nfs4_client *clp = ls->ls_stid.sc_client;
    > > > char addr_str[INET6_ADDRSTRLEN];
    > > > + static char const nfsd_recall_failed[] = "/sbin/nfsd-recall-failed";
    > > > static char *envp[] = {
    > > > "HOME=/",
    > > > "TERM=linux",
    > > > @@ -628,12 +629,13 @@ nfsd4_cb_layout_fail(struct nfs4_layout_stateid *ls)
    > > > "nfsd: client %s failed to respond to layout recall. "
    > > > " Fencing..\n", addr_str);
    > > >
    > > > - argv[0] = "/sbin/nfsd-recall-failed";
    > > > + argv[0] = (char *)nfsd_recall_failed;
    > > > argv[1] = addr_str;
    > > > argv[2] = ls->ls_file->f_path.mnt->mnt_sb->s_id;
    > > > argv[3] = NULL;
    > > >
    > > > - error = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);
    > > > + error = call_usermodehelper(nfsd_recall_failed, argv, envp,
    > > > + UMH_WAIT_PROC);
    > > > if (error) {
    > > > printk(KERN_ERR "nfsd: fence failed for client %s: %d!\n",
    > > > addr_str, error);
    > >
    > > Do we need a similar fix in nfsd4_umh_cltrack_upcall?
    >
    > Not that I can tell, as the call_usermodehelper() binary it calls is
    > dynamically created (it's not a static string). Unless I'm misreading
    > the code?
    >

    It's a module_param_string:

    static char cltrack_prog[PATH_MAX] = "/sbin/nfsdcltrack";
    module_param_string(cltrack_prog, cltrack_prog, sizeof(cltrack_prog),
                            S_IRUGO|S_IWUSR);
    MODULE_PARM_DESC(cltrack_prog, "Path to the nfsdcltrack upcall
    program");

    Maybe we should consider deprecating that module parameter and make it
    const as well? I added it when I first developed that code, but I doubt
    anyone legitimately sets it.

    --
    Jeff Layton <jlayton@poochiereds.net>

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