coredump: use from_kuid/kgid when formatting corename

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.

Use init_user_ns in order not to break existing ABI, and document this in
Documentation/sysctl/kernel.txt.

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>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index e5d528e0c46e88fa8ca7050f40f70213aebc7204..6fccb69c03e747c2eb713a1256676c8fa44f2349 100644 (file)
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -197,8 +197,8 @@ core_pattern is used to specify a core dumpfile pattern name.
        %P      global pid (init PID namespace)
        %i      tid
        %I      global tid (init PID namespace)
-       %u      uid
-       %g      gid
+       %u      uid (in initial user namespace)
+       %g      gid (in initial user namespace)
        %d      dump mode, matches PR_SET_DUMPABLE and
                /proc/sys/fs/suid_dumpable
        %s      signal number

diff --git a/fs/coredump.c b/fs/coredump.c
index bbbe139ab28020244f62011f44869d1529cd4b05..833a57bc856c9bb1ec0f9aa734c46b1bc79c90dc 100644 (file)
--- 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(&init_user_ns,
+                                                         cred->uid));
                                break;
                        /* gid */
                        case 'g':
-                               err = cn_printf(cn, "%d", cred->gid);
+                               err = cn_printf(cn, "%u",
+                                               from_kgid(&init_user_ns,
+                                                         cred->gid));
                                break;
                        case 'd':
                                err = cn_printf(cn, "%d",