kernel: make groups_sort calling a responsibility group_info allocators

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@gmail.com
Signed-off-by: Thiago Rafael Becker <thiago.becker@gmail.com>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: NeilBrown <neilb@suse.com>
Acked-by: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c
index f04db3779b34507f9dd38791fc89131505d5f0c3..59eea9c65d3e9e8595d509001b1c794420060887 100644 (file)
--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -263,6 +263,7 @@ COMPAT_SYSCALL_DEFINE2(s390_setgroups16, int, gidsetsize, u16 __user *, grouplis
                return retval;
        }
 
+       groups_sort(group_info);
        retval = set_current_groups(group_info);
        put_group_info(group_info);
 

diff --git a/fs/nfsd/auth.c b/fs/nfsd/auth.c
index 697f8ae7792d1304e3cec035fd56185eb2ee02df..f650e475d8f0d84af1bb3013b6b35ef77421cde2 100644 (file)
--- a/fs/nfsd/auth.c
+++ b/fs/nfsd/auth.c
@@ -60,6 +60,9 @@ int nfsd_setuser(struct svc_rqst *rqstp, struct svc_export *exp)
                                gi->gid[i] = exp->ex_anon_gid;
                        else
                                gi->gid[i] = rqgi->gid[i];
+
+                       /* Each thread allocates its own gi, no race */
+                       groups_sort(gi);
                }
        } else {
                gi = get_group_info(rqgi);

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 099058e1178b4d8529438450e28ad03b06497d32..631286535d0f126a13a366b924cae62f58d114e1 100644 (file)
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -83,6 +83,7 @@ extern int set_current_groups(struct group_info *);
 extern void set_groups(struct cred *, struct group_info *);
 extern int groups_search(const struct group_info *, kgid_t);
 extern bool may_setgroups(void);
+extern void groups_sort(struct group_info *);
 
 /*
  * The security context of a task

diff --git a/kernel/groups.c b/kernel/groups.c
index e357bc800111043ed8d477d758bd245b8aa4c566..daae2f2dc6d4f64565112f0d7fea9c984887ce26 100644 (file)
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -86,11 +86,12 @@ static int gid_cmp(const void *_a, const void *_b)
        return gid_gt(a, b) - gid_lt(a, b);
 }
 
-static void groups_sort(struct group_info *group_info)
+void groups_sort(struct group_info *group_info)
 {
        sort(group_info->gid, group_info->ngroups, sizeof(*group_info->gid),
             gid_cmp, NULL);
 }
+EXPORT_SYMBOL(groups_sort);
 
 /* a simple bsearch */
 int groups_search(const struct group_info *group_info, kgid_t grp)
@@ -122,7 +123,6 @@ int groups_search(const struct group_info *group_info, kgid_t grp)
 void 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;
 }
@@ -206,6 +206,7 @@ SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
                return retval;
        }
 
+       groups_sort(group_info);
        retval = set_current_groups(group_info);
        put_group_info(group_info);
 

diff --git a/kernel/uid16.c b/kernel/uid16.c
index ce74a4901d2b058595af031cf6c408c48dc5e1f1..ef1da2a5f9bd00689e4f78adffb04c867d8395cb 100644 (file)
--- a/kernel/uid16.c
+++ b/kernel/uid16.c
@@ -192,6 +192,7 @@ SYSCALL_DEFINE2(setgroups16, int, gidsetsize, old_gid_t __user *, grouplist)
                return retval;
        }
 
+       groups_sort(group_info);
        retval = set_current_groups(group_info);
        put_group_info(group_info);
 

diff --git a/net/sunrpc/auth_gss/gss_rpc_xdr.c b/net/sunrpc/auth_gss/gss_rpc_xdr.c
index c4778cae58ef12c191958261a50e58e5f67082e8..444380f968f1158660f6a01a10cd8223c9db6081 100644 (file)
--- a/net/sunrpc/auth_gss/gss_rpc_xdr.c
+++ b/net/sunrpc/auth_gss/gss_rpc_xdr.c
@@ -231,6 +231,7 @@ static int gssx_dec_linux_creds(struct xdr_stream *xdr,
                        goto out_free_groups;
                creds->cr_group_info->gid[i] = kgid;
        }
+       groups_sort(creds->cr_group_info);
 
        return 0;
 out_free_groups:

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 5dd4e6c9fef21f650db78907e0fa46ee09413c71..26531193fce4d07f4b6d513093544b4a760f96ab 100644 (file)
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -481,6 +481,7 @@ static int rsc_parse(struct cache_detail *cd,
                                goto out;
                        rsci.cred.cr_group_info->gid[i] = kgid;
                }
+               groups_sort(rsci.cred.cr_group_info);
 
                /* mech name */
                len = qword_get(&mesg, buf, mlen);

diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 740b67d5a733bdcd1ad10b6efdf957a8cd9a7889..af7f28fb8102e4313f5ced6aa585e30f3911ca6c 100644 (file)
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -520,6 +520,7 @@ static int unix_gid_parse(struct cache_detail *cd,
                ug.gi->gid[i] = kgid;
        }
 
+       groups_sort(ug.gi);
        ugp = unix_gid_lookup(cd, uid);
        if (ugp) {
                struct cache_head *ch;
@@ -819,6 +820,7 @@ svcauth_unix_accept(struct svc_rqst *rqstp, __be32 *authp)
                kgid_t kgid = make_kgid(&init_user_ns, svc_getnl(argv));
                cred->cr_group_info->gid[i] = kgid;
        }
+       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;