[PATCH 3.2 046/140] kernel: make groups_sort calling a responsibility group_info allocators

[Ben Hutchings]

3.2.100-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Thiago Rafael Becker <thiago.becker@xxxxxxxxx>

commit bdcf0a423ea1c40bbb40e7ee483b50fc8aa3d758 upstream.

In testing, we found that nfsd threads may call set_groups in parallel
for the same entry cached in auth.unix.gid, racing in the call of
groups_sort, corrupting the groups for that entry and leading to
permission denials for the client.

This patch:
 - Make groups_sort globally visible.
 - Move the call to groups_sort to the modifiers of group_info
 - Remove the call to groups_sort from set_groups

Link: http://lkml.kernel.org/r/20171211151420.18655-1-thiago.becker@xxxxxxxxx
Signed-off-by: Thiago Rafael Becker <thiago.becker@xxxxxxxxx>
Reviewed-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Reviewed-by: NeilBrown <neilb@xxxxxxxx>
Acked-by: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2:
 - Drop change in gss_rpc_xdr.c
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -242,6 +242,7 @@ asmlinkage long sys32_setgroups16(int gi
 		return retval;
 	}
 
+	groups_sort(group_info);
 	retval = set_current_groups(group_info);
 	put_group_info(group_info);
 
--- a/fs/nfsd/auth.c
+++ b/fs/nfsd/auth.c
@@ -60,6 +60,9 @@ int nfsd_setuser(struct svc_rqst *rqstp,
 				GROUP_AT(gi, i) = exp->ex_anon_gid;
 			else
 				GROUP_AT(gi, i) = GROUP_AT(rqgi, i);
+
+			/* Each thread allocates its own gi, no race */
+			groups_sort(gi);
 		}
 	} else {
 		gi = get_group_info(rqgi);
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -67,6 +67,7 @@ extern void groups_free(struct group_inf
 extern int set_current_groups(struct group_info *);
 extern int set_groups(struct cred *, struct group_info *);
 extern int groups_search(const struct group_info *, gid_t);
+extern void groups_sort(struct group_info *);
 
 /* access the groups "array" with this macro */
 #define GROUP_AT(gi, i) \
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -103,7 +103,7 @@ static int groups_from_user(struct group
 }
 
 /* a simple Shell sort */
-static void groups_sort(struct group_info *group_info)
+void groups_sort(struct group_info *group_info)
 {
 	int base, max, stride;
 	int gidsetsize = group_info->ngroups;
@@ -130,6 +130,7 @@ static void groups_sort(struct group_inf
 		stride /= 3;
 	}
 }
+EXPORT_SYMBOL(groups_sort);
 
 /* a simple bsearch */
 int groups_search(const struct group_info *group_info, gid_t grp)
@@ -164,7 +165,6 @@ int groups_search(const struct group_inf
 int set_groups(struct cred *new, struct group_info *group_info)
 {
 	put_group_info(new->group_info);
-	groups_sort(group_info);
 	get_group_info(group_info);
 	new->group_info = group_info;
 	return 0;
@@ -247,6 +247,7 @@ SYSCALL_DEFINE2(setgroups, int, gidsetsi
 		return retval;
 	}
 
+	groups_sort(group_info);
 	retval = set_current_groups(group_info);
 	put_group_info(group_info);
 
--- a/kernel/uid16.c
+++ b/kernel/uid16.c
@@ -203,6 +203,7 @@ SYSCALL_DEFINE2(setgroups16, int, gidset
 		return retval;
 	}
 
+	groups_sort(group_info);
 	retval = set_current_groups(group_info);
 	put_group_info(group_info);
 
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -477,6 +477,7 @@ static int rsc_parse(struct cache_detail
 				goto out;
 			GROUP_AT(rsci.cred.cr_group_info, i) = gid;
 		}
+		groups_sort(rsci.cred.cr_group_info);
 
 		/* mech name */
 		len = qword_get(&mesg, buf, mlen);
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -539,6 +539,7 @@ static int unix_gid_parse(struct cache_d
 		GROUP_AT(ug.gi, i) = gid;
 	}
 
+	groups_sort(ug.gi);
 	ugp = unix_gid_lookup(uid);
 	if (ugp) {
 		struct cache_head *ch;
@@ -806,6 +807,7 @@ svcauth_unix_accept(struct svc_rqst *rqs
 		return SVC_CLOSE;
 	for (i = 0; i < slen; i++)
 		GROUP_AT(cred->cr_group_info, i) = svc_getnl(argv);
+	groups_sort(cred->cr_group_info);
 	if (svc_getu32(argv) != htonl(RPC_AUTH_NULL) || svc_getu32(argv) != 0) {
 		*authp = rpc_autherr_badverf;
 		return SVC_DENIED;