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@xxxxxxx>
---
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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