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    Subject[PATCH 3.18 66/84] userns: Unbreak the unprivileged remount tests
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: "Eric W. Biederman" <ebiederm@xmission.com>

    commit db86da7cb76f797a1a8b445166a15cb922c6ff85 upstream.

    A security fix in caused the way the unprivileged remount tests were
    using user namespaces to break. Tweak the way user namespaces are
    being used so the test works again.

    Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    tools/testing/selftests/mount/unprivileged-remount-test.c | 32 ++++++++++----
    1 file changed, 24 insertions(+), 8 deletions(-)

    --- a/tools/testing/selftests/mount/unprivileged-remount-test.c
    +++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
    @@ -53,17 +53,14 @@ static void die(char *fmt, ...)
    exit(EXIT_FAILURE);
    }

    -static void write_file(char *filename, char *fmt, ...)
    +static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
    {
    char buf[4096];
    int fd;
    ssize_t written;
    int buf_len;
    - va_list ap;

    - va_start(ap, fmt);
    buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
    - va_end(ap);
    if (buf_len < 0) {
    die("vsnprintf failed: %s\n",
    strerror(errno));
    @@ -74,6 +71,8 @@ static void write_file(char *filename, c

    fd = open(filename, O_WRONLY);
    if (fd < 0) {
    + if ((errno == ENOENT) && enoent_ok)
    + return;
    die("open of %s failed: %s\n",
    filename, strerror(errno));
    }
    @@ -92,6 +91,26 @@ static void write_file(char *filename, c
    }
    }

    +static void maybe_write_file(char *filename, char *fmt, ...)
    +{
    + va_list ap;
    +
    + va_start(ap, fmt);
    + vmaybe_write_file(true, filename, fmt, ap);
    + va_end(ap);
    +
    +}
    +
    +static void write_file(char *filename, char *fmt, ...)
    +{
    + va_list ap;
    +
    + va_start(ap, fmt);
    + vmaybe_write_file(false, filename, fmt, ap);
    + va_end(ap);
    +
    +}
    +
    static int read_mnt_flags(const char *path)
    {
    int ret;
    @@ -144,13 +163,10 @@ static void create_and_enter_userns(void
    strerror(errno));
    }

    + maybe_write_file("/proc/self/setgroups", "deny");
    write_file("/proc/self/uid_map", "0 %d 1", uid);
    write_file("/proc/self/gid_map", "0 %d 1", gid);

    - if (setgroups(0, NULL) != 0) {
    - die("setgroups failed: %s\n",
    - strerror(errno));
    - }
    if (setgid(0) != 0) {
    die ("setgid(0) failed %s\n",
    strerror(errno));



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