Return-Path: Received: from mx143.netapp.com ([216.240.21.24]:56394 "EHLO mx143.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751507AbcDZNeZ (ORCPT ); Tue, 26 Apr 2016 09:34:25 -0400 From: Olga Kornievskaia To: CC: Subject: [PATCH v4 2/3] gssd: using syscalls directly to change thread's identity Date: Tue, 26 Apr 2016 09:34:14 -0400 Message-ID: <1461677655-68294-3-git-send-email-kolga@netapp.com> In-Reply-To: <1461677655-68294-1-git-send-email-kolga@netapp.com> References: <1461677655-68294-1-git-send-email-kolga@netapp.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-nfs-owner@vger.kernel.org List-ID: For the threaded version we have to set uid,gid per thread instead of per process. glibc setresuid() when called from a thread, it'll send a signal to all other threads to synchronize the uid in all other threads. To bypass this, we have to call syscall() directly. Signed-off-by: Olga Kornievskaia Reviewed-by: Steve Dickson --- utils/gssd/gssd_proc.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/utils/gssd/gssd_proc.c b/utils/gssd/gssd_proc.c index e2e95dc..39c4b17 100644 --- a/utils/gssd/gssd_proc.c +++ b/utils/gssd/gssd_proc.c @@ -69,6 +69,7 @@ #include #include #include +#include #include "gssd.h" #include "err_util.h" @@ -436,7 +437,7 @@ change_identity(uid_t uid) struct passwd *pw; /* drop list of supplimentary groups first */ - if (setgroups(0, NULL) != 0) { + if (syscall(SYS_setgroups, 0, 0) != 0) { printerr(0, "WARNING: unable to drop supplimentary groups!"); return errno; } @@ -457,7 +458,12 @@ change_identity(uid_t uid) * Switch the GIDs. Note that we leave the saved-set-gid alone in an * attempt to prevent attacks via ptrace() */ - if (setresgid(pw->pw_gid, pw->pw_gid, -1) != 0) { + /* For the threaded version we have to set uid,gid per thread instead + * of per process. glibc setresuid() when called from a thread, it'll + * send a signal to all other threads to synchronize the uid in all + * other threads. To bypass this, we have to call syscall() directly. + */ + if (syscall(SYS_setresgid, pw->pw_gid, -1, -1) != 0) { printerr(0, "WARNING: failed to set gid to %u!\n", pw->pw_gid); return errno; } @@ -466,7 +472,7 @@ change_identity(uid_t uid) * Switch UIDs, but leave saved-set-uid alone to prevent ptrace() by * other processes running with this uid. */ - if (setresuid(uid, uid, -1) != 0) { + if (syscall(SYS_setresuid, uid, -1, -1) != 0) { printerr(0, "WARNING: Failed to setuid for user with uid %u\n", uid); return errno; -- 1.8.3.1