Return-Path: Received: from mx2.suse.de ([195.135.220.15]:38399 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750978AbeBSFDR (ORCPT ); Mon, 19 Feb 2018 00:03:17 -0500 From: NeilBrown To: Trond Myklebust , Anna Schumaker Date: Mon, 19 Feb 2018 16:02:28 +1100 Subject: [PATCH 01/23] cred: add cred_fscmp() for comparing creds. Cc: linux-nfs@vger.kernel.org Message-ID: <151901654877.17421.12826958279097933802.stgit@noble> In-Reply-To: <151901634940.17421.7637564368419392071.stgit@noble> References: <151901634940.17421.7637564368419392071.stgit@noble> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Sender: linux-nfs-owner@vger.kernel.org List-ID: NFS needs to compare to credentials, to see if they can be treated the same w.r.t. filesystem access. Sometimes an ordering is needed when credentials are used as a key to an rbtree. NFS current has its own private credential management from before 'struct cred' existed. To move it over to more consistent use of 'struct cred' we need a comparison function. This patch adds that function. Signed-off-by: NeilBrown --- include/linux/cred.h | 1 + kernel/cred.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 56 insertions(+) diff --git a/include/linux/cred.h b/include/linux/cred.h index 631286535d0f..6dd51e503f23 100644 --- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -164,6 +164,7 @@ extern int change_create_files_as(struct cred *, struct inode *); extern int set_security_override(struct cred *, u32); extern int set_security_override_from_ctx(struct cred *, const char *); extern int set_create_files_as(struct cred *, struct inode *); +extern int cred_fscmp(const struct cred *, const struct cred *); extern void __init cred_init(void); /* diff --git a/kernel/cred.c b/kernel/cred.c index ecf03657e71c..4ce75c6fb752 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -19,6 +19,7 @@ #include #include #include +#include #if 0 #define kdebug(FMT, ...) \ @@ -564,6 +565,60 @@ void revert_creds(const struct cred *old) } EXPORT_SYMBOL(revert_creds); +/** + * cred_fscmp - Compare to credentials with respect to filesystem access. + * @a: The first credential + * @b: The second credential + * + * cred_cmp() will return zero if both credentials have the same + * fsuid, fsgid, and supplementary groups. That is, if they will both + * provide the same access to files based on mode/uid/gid. + * If the credentials are different, then either -1 or 1 will + * be returned depending on whether @a comes before or after @b + * respectively in an arbitrary, but stable, ordering of credentials. + * + * Return: -1, 0, or 1 depending on comparison + */ +int cred_fscmp(const struct cred *a, const struct cred *b) +{ + struct group_info *ga, *gb; + int g; + + if (a == b) + return 0; + if (uid_lt(a->fsuid, b->fsuid)) + return -1; + if (uid_gt(a->fsuid, b->fsuid)) + return 1; + + if (gid_lt(a->fsgid, b->fsgid)) + return -1; + if (gid_gt(a->fsgid, b->fsgid)) + return 1; + + ga = a->group_info; + gb = b->group_info; + if (ga == gb) + return 0; + if (ga == NULL) + return -1; + if (gb == NULL) + return 1; + if (ga->ngroups < gb->ngroups) + return -1; + if (ga->ngroups > gb->ngroups) + return 1; + + for (g = 0; g < ga->ngroups; g++) { + if (gid_lt(ga->gid[g], gb->gid[g])) + return -1; + if (gid_gt(ga->gid[g], gb->gid[g])) + return 1; + } + return 0; +} +EXPORT_SYMBOL(cred_fscmp); + /* * initialise the credentials stuff */