2 files changed, 10 insertions, 1 deletions

diff --git a/config-daemon.ac b/config-daemon.ac
index 4e949bc88a3..35d9c8cd56b 100644
--- a/config-daemon.ac
+++ b/config-daemon.ac
@@ -79,7 +79,7 @@ if test "x$guix_build_daemon" = "xyes"; then
   dnl Chroot support.
   AC_CHECK_FUNCS([chroot unshare])
   AC_CHECK_HEADERS([sched.h sys/param.h sys/mount.h sys/syscall.h \
-    linux/close_range.h])
+    linux/close_range.h sys/prctl.h])
 
   if test "x$ac_cv_func_chroot" != "xyes"; then
     AC_MSG_ERROR(['chroot' function missing, bailing out])
diff --git a/nix/libstore/build.cc b/nix/libstore/build.cc
index 2261ef3c2a0..e6a139eb0d7 100644
--- a/nix/libstore/build.cc
+++ b/nix/libstore/build.cc
@@ -50,6 +50,9 @@
 #if HAVE_SCHED_H
 #include <sched.h>
 #endif
+#if HAVE_SYS_PRCTL_H
+#include <sys/prctl.h>
+#endif
 
 
 #define CHROOT_ENABLED HAVE_CHROOT && HAVE_SYS_MOUNT_H && defined(MS_BIND) && defined(MS_PRIVATE)
@@ -2075,6 +2078,12 @@ void DerivationGoal::runChild()
 
 #if CHROOT_ENABLED
         if (useChroot) {
+# if HAVE_SYS_PRCTL_H
+            /* Drop ambient capabilities such as CAP_CHOWN that might have
+               been granted when starting guix-daemon.  */
+            prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0);
+# endif
+
             if (!fixedOutput) {
                 /* Initialise the loopback interface. */
                 AutoCloseFD fd(socket(PF_INET, SOCK_DGRAM, IPPROTO_IP));