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@xxxxxxx>
---
Documentation/sysctl/kernel.txt | 4 ++--
fs/coredump.c | 8 ++++++--
2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index c831001c45f1..e1913f78f21e 100644
--- 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 bbbe139ab280..833a57bc856c 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(&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",
--
2.4.0
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