Add __printf attributes to cn_*printf functions.  With these, gcc says:

  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);
       ^
  fs/coredump.c:225:5: warning: format '%ld' expects argument of type
  'long int', but argument 3 has type 'int' [-Wformat=]
       err = cn_printf(cn, "%ld", cprm->siginfo->si_signo);
       ^

The third warning is easily fixed as si_signo is always an int.

For the two others, cred->uid and cred->gid need to be converted to
either a 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 current process namespace, it seems intuitive
that lowercase %u and %g use the current user namespace.  So implement
this.

Signed-off-by: Nicolas Iooss <[email protected]>
---

I sent this patch more than a month ago but go no feedback, so I'm sending it 
again.
Comments would be greatly appreciated.

 fs/coredump.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index bbbe139ab280..977fc8b91f2d 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -70,7 +70,8 @@ static int expand_corename(struct core_name *cn, int size)
        return 0;
 }
 
-static int cn_vprintf(struct core_name *cn, const char *fmt, va_list arg)
+static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
+                                    va_list arg)
 {
        int free, need;
        va_list arg_copy;
@@ -93,7 +94,7 @@ again:
        return -ENOMEM;
 }
 
-static int cn_printf(struct core_name *cn, const char *fmt, ...)
+static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
 {
        va_list arg;
        int ret;
@@ -105,7 +106,8 @@ static int cn_printf(struct core_name *cn, const char *fmt, 
...)
        return ret;
 }
 
-static int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
+static __printf(2, 3)
+int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
 {
        int cur = cn->used;
        va_list arg;
@@ -209,11 +211,15 @@ 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, "%d",
+                                               from_kuid_munged(cred->user_ns,
+                                                                cred->uid));
                                break;
                        /* gid */
                        case 'g':
-                               err = cn_printf(cn, "%d", cred->gid);
+                               err = cn_printf(cn, "%d",
+                                               from_kgid_munged(cred->user_ns,
+                                                                cred->gid));
                                break;
                        case 'd':
                                err = cn_printf(cn, "%d",
@@ -221,7 +227,7 @@ static int format_corename(struct core_name *cn, struct 
coredump_params *cprm)
                                break;
                        /* signal that caused the coredump */
                        case 's':
-                               err = cn_printf(cn, "%ld", 
cprm->siginfo->si_signo);
+                               err = cn_printf(cn, "%d", 
cprm->siginfo->si_signo);
                                break;
                        /* UNIX time of coredump */
                        case 't': {
-- 
2.3.5

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