From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1BF33C169C4 for ; Fri, 8 Feb 2019 16:46:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E771B2080F for ; Fri, 8 Feb 2019 16:46:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726869AbfBHQqS (ORCPT ); Fri, 8 Feb 2019 11:46:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49328 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726679AbfBHQqS (ORCPT ); Fri, 8 Feb 2019 11:46:18 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 741C36EB93; Fri, 8 Feb 2019 16:46:17 +0000 (UTC) Received: from localhost (unknown [10.43.12.40]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AA6121077D1C; Fri, 8 Feb 2019 16:46:16 +0000 (UTC) References: <20190206194529.24952-1-plautrba@redhat.com> User-agent: mu4e 1.0; emacs 26.1 From: Petr Lautrbach To: selinux@vger.kernel.org Cc: Petr Lautrbach , Nicolas Iooss Subject: Re: [PATCH] libsemanage: genhomedircon - improve handling large groups In-reply-to: Date: Fri, 08 Feb 2019 17:46:15 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; format=flowed X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Fri, 08 Feb 2019 16:46:17 +0000 (UTC) Sender: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org Nicolas Iooss writes: > On Wed, Feb 6, 2019 at 8:45 PM Petr Lautrbach > wrote: >> >> getgrnam_r() uses a preallocated buffer to store a structure >> containing >> the broken-out fields of the record in the group database. The >> size of >> this buffer is usually sysconf(_SC_GETGR_R_SIZE_MAX) == 1024 >> and it is >> not enough for groups with a large number of users. In these >> cases, >> getgrnam_r() returns -1 and sets errno to ERANGE and the caller >> can >> retry with a larger buffer. >> >> Fixes: >> $ semanage login -a -s user_u -r s0-s0:c1.c2 '%largegroup' >> libsemanage.semanage_direct_commit: semanage_genhomedircon >> returned error code -1. (Numerical result out of range). >> OSError: Numerical result out of range >> >> Signed-off-by: Petr Lautrbach >> --- >> libsemanage/src/genhomedircon.c | 16 +++++++++++++--- >> 1 file changed, 13 insertions(+), 3 deletions(-) >> >> diff --git a/libsemanage/src/genhomedircon.c >> b/libsemanage/src/genhomedircon.c >> index 591941fb..ac376671 100644 >> --- a/libsemanage/src/genhomedircon.c >> +++ b/libsemanage/src/genhomedircon.c >> @@ -1077,10 +1077,20 @@ static int >> get_group_users(genhomedircon_settings_t * s, >> >> const char *grname = selogin + 1; >> >> - if (getgrnam_r(grname, &grstorage, grbuf, >> - (size_t) grbuflen, &group) != 0) { >> - goto cleanup; >> + errno = 0; >> + while ( >> + (retval = getgrnam_r(grname, &grstorage, grbuf, >> (size_t) grbuflen, &group)) != 0 && >> + errno == ERANGE >> + ) { >> + char *new_grbuf; >> + grbuflen *= 2; >> + new_grbuf = realloc(grbuf, grbuflen); >> + if (new_grbuf == NULL) >> + goto cleanup; >> + grbuf = new_grbuf; >> } > > Hello, > When reading this for loop, I am concerned about the case where > the > member list exceeds 2Go on a system with a 32-bit CPU (where > sizeof(long) = 4). Even if it seems very unlikely, if this ever > happens, the loop will become infinite. Would you agree with > adding > "&& grbuflen > 0" to the condition of the while statement? Makes sense, I'll add it. Thanks. > Anyway, if you do not agree, this patch looks good to me. > Acked-by: Nicolas Iooss > > Thanks, > Nicolas > >> + if (retval == -1) >> + goto cleanup; According to the man page this check is not correct. - "In case of error, an error number is returned, and NULL is stored in *result." I'll fix it as well. >> if (group == NULL) { >> ERR(s->h_semanage, "Can't find group named >> %s\n", grname); >> -- >> 2.20.1 >>