[PATCH 2/2] cifs.upall: update the cap bounding set only when CAP_SETPCAP is given

[Jonas Witschel <diabonas@archlinux.org>]

libcap-ng 0.8.1 tightened the error checking on capng_apply, returning an error
of -4 when trying to update the capability bounding set without having the
CAP_SETPCAP capability to be able to do so. Previous versions of libcap-ng
silently skipped updating the bounding set and only updated the normal
CAPNG_SELECT_CAPS capabilities instead.

Check beforehand whether we have CAP_SETPCAP, in which case we can use
CAPNG_SELECT_BOTH to update both the normal capabilities and the bounding set.
Otherwise, we can at least update the normal capabilities, but refrain from
trying to update the bounding set to avoid getting an error.

Signed-off-by: Jonas Witschel <diabonas@archlinux.org>
---
 cifs.upcall.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/cifs.upcall.c b/cifs.upcall.c
index 1559434..af1a0b0 100644
--- a/cifs.upcall.c
+++ b/cifs.upcall.c
@@ -88,6 +88,8 @@ typedef enum _sectype {
 static int
 trim_capabilities(bool need_environ)
 {
+	capng_select_t set = CAPNG_SELECT_CAPS;
+
 	capng_clear(CAPNG_SELECT_BOTH);
 
 	/* SETUID and SETGID to change uid, gid, and grouplist */
@@ -105,7 +107,10 @@ trim_capabilities(bool need_environ)
 		return 1;
 	}
 
-	if (capng_apply(CAPNG_SELECT_BOTH)) {
+	if (capng_have_capability(CAPNG_EFFECTIVE, CAP_SETPCAP)) {
+		set = CAPNG_SELECT_BOTH;
+	}
+	if (capng_apply(set)) {
 		syslog(LOG_ERR, "%s: Unable to apply capability set: %m\n", __func__);
 		return 1;
 	}
-- 
2.29.2