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    Subject[PATCH 1/2] coredump: use from_kuid/kgid_munged when formatting corename
    Date
    When adding __printf attribute to cn_printf, gcc reports some issues:

    fs/coredump.c:213:5: warning: format '%d' expects argument of type
    'int', but argument 3 has type 'kuid_t' [-Wformat=]
    err = cn_printf(cn, "%d", cred->uid);
    ^
    fs/coredump.c:217:5: warning: format '%d' expects argument of type
    'int', but argument 3 has type 'kgid_t' [-Wformat=]
    err = cn_printf(cn, "%d", cred->gid);
    ^

    These warnings come from the fact that the value of uid/gid needs to be
    extracted from the kuid_t/kgid_t structure before being used as an
    integer. More precisely, cred->uid and cred->gid need to be converted
    to either user-namespace uid/gid or to init_user_ns uid/gid.

    As Documentation/sysctl/kernel.txt does not specify which user namespace
    is used to translate %u and %g in core_pattern, but lowercase %p and %i
    are used to format pid/tid in the current process namespace, it seems
    intuitive that lowercase %u and %g use the current user namespace.

    While at it, format uid and gid values with %u instead of %d because
    uid_t/__kernel_uid32_t and gid_t/__kernel_gid32_t are unsigned int.

    Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
    ---
    fs/coredump.c | 8 ++++++--
    1 file changed, 6 insertions(+), 2 deletions(-)

    diff --git a/fs/coredump.c b/fs/coredump.c
    index bbbe139ab280..99c8af640c5a 100644
    --- a/fs/coredump.c
    +++ b/fs/coredump.c
    @@ -209,11 +209,15 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm)
    break;
    /* uid */
    case 'u':
    - err = cn_printf(cn, "%d", cred->uid);
    + err = cn_printf(cn, "%u",
    + from_kuid_munged(cred->user_ns,
    + cred->uid));
    break;
    /* gid */
    case 'g':
    - err = cn_printf(cn, "%d", cred->gid);
    + err = cn_printf(cn, "%u",
    + from_kgid_munged(cred->user_ns,
    + cred->gid));
    break;
    case 'd':
    err = cn_printf(cn, "%d",
    --
    2.3.6


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