Add kern_setgroups() and kern_getgroups() and use them to implement

ibcs2_[gs]etgroups() rather than using the stackgap.  This also makes
ibcs2_[gs]etgroups() MPSAFE.  Also, it cleans up one bit of weirdness in
the old setgroups() where it allocated an entire credential just so it had
a place to copy the group list into.  Now setgroups just allocates a
NGROUPS_MAX array on the stack that it copies into and then passes to
kern_setgroups().

4 files changed, 71 insertions, 69 deletions

diff --git a/sys/i386/ibcs2/ibcs2_misc.c b/sys/i386/ibcs2/ibcs2_misc.c
index c4efc02..c875075 100644
--- a/sys/i386/ibcs2/ibcs2_misc.c
+++ b/sys/i386/ibcs2/ibcs2_misc.c
@@ -651,35 +651,25 @@ ibcs2_getgroups(td, uap)
 	struct thread *td;
 	struct ibcs2_getgroups_args *uap;
 {
-	int error, i;
-	ibcs2_gid_t *iset = NULL;
-	struct getgroups_args sa;
-	gid_t *gp;
-	caddr_t sg = stackgap_init();
+	ibcs2_gid_t iset[NGROUPS_MAX];
+	gid_t gp[NGROUPS_MAX];
+	u_int i, ngrp;
+	int error;
 
 	if (uap->gidsetsize < 0)
 		return (EINVAL);
-	if (uap->gidsetsize > NGROUPS_MAX)
-		uap->gidsetsize = NGROUPS_MAX;
-	sa.gidsetsize = uap->gidsetsize;
-	if (uap->gidsetsize) {
-		sa.gidset = stackgap_alloc(&sg, NGROUPS_MAX *
-						    sizeof(gid_t *));
-		iset = stackgap_alloc(&sg, uap->gidsetsize *
-				      sizeof(ibcs2_gid_t));
+	ngrp = MIN(uap->gidsetsize, NGROUPS_MAX);
+	error = kern_getgroups(td, &ngrp, gp);
+	if (error)
+		return (error);
+	if (uap->gidsetsize > 0) {
+		for (i = 0; i < ngrp; i++)
+			iset[i] = (ibcs2_gid_t)gp[i];
+		error = copyout(iset, uap->gidset, ngrp * sizeof(ibcs2_gid_t));
 	}
-	if ((error = getgroups(td, &sa)) != 0)
-		return error;
-	if (uap->gidsetsize == 0)
-		return 0;
-
-	for (i = 0, gp = sa.gidset; i < td->td_retval[0]; i++)
-		iset[i] = (ibcs2_gid_t)*gp++;
-	if (td->td_retval[0] && (error = copyout((caddr_t)iset,
-					  (caddr_t)uap->gidset,
-					  sizeof(ibcs2_gid_t) * td->td_retval[0])))
-		return error;
-        return 0;
+	if (error == 0)
+		td->td_retval[0] = ngrp;
+	return (error);
 }
 
 int
@@ -687,28 +677,21 @@ ibcs2_setgroups(td, uap)
 	struct thread *td;
 	struct ibcs2_setgroups_args *uap;
 {
+	ibcs2_gid_t iset[NGROUPS_MAX];
+	gid_t gp[NGROUPS_MAX];
 	int error, i;
-	ibcs2_gid_t *iset;
-	struct setgroups_args sa;
-	gid_t *gp;
-	caddr_t sg = stackgap_init();
 
 	if (uap->gidsetsize < 0 || uap->gidsetsize > NGROUPS_MAX)
 		return (EINVAL);
-	sa.gidsetsize = uap->gidsetsize;
-	sa.gidset = stackgap_alloc(&sg, sa.gidsetsize *
-					    sizeof(gid_t *));
-	iset = stackgap_alloc(&sg, sa.gidsetsize *
-			      sizeof(ibcs2_gid_t *));
-	if (sa.gidsetsize) {
-		if ((error = copyin((caddr_t)uap->gidset, (caddr_t)iset, 
-				   sizeof(ibcs2_gid_t *) *
-				   uap->gidsetsize)) != 0)
-			return error;
+	if (uap->gidsetsize && uap->gidset) {
+		error = copyin(uap->gidset, iset, sizeof(ibcs2_gid_t) *
+		    uap->gidsetsize);
+		if (error)
+			return (error);
+		for (i = 0; i < uap->gidsetsize; i++)
+			gp[i] = (gid_t)iset[i];
 	}
-	for (i = 0, gp = sa.gidset; i < sa.gidsetsize; i++)
-		*gp++ = (gid_t)iset[i];
-	return setgroups(td, &sa);
+	return (kern_setgroups(td, uap->gidsetsize, gp));
 }
 
 int
diff --git a/sys/i386/ibcs2/syscalls.xenix b/sys/i386/ibcs2/syscalls.xenix
index ae8be83..8b9b84a 100644
--- a/sys/i386/ibcs2/syscalls.xenix
+++ b/sys/i386/ibcs2/syscalls.xenix
@@ -56,9 +56,9 @@
 				    ibcs2_sigset_t *oset); }
 41	AUE_NULL	MSTD	{ int ibcs2_sigpending(ibcs2_sigset_t *mask); }
 42	AUE_NULL	MSTD	{ int ibcs2_sigsuspend(ibcs2_sigset_t *mask); }
-43	AUE_GETGROUPS	STD	{ int ibcs2_getgroups(int gidsetsize, \
+43	AUE_GETGROUPS	MSTD	{ int ibcs2_getgroups(int gidsetsize, \
 				    ibcs2_gid_t *gidset); }
-44	AUE_SETGROUPS	STD	{ int ibcs2_setgroups(int gidsetsize, \
+44	AUE_SETGROUPS	MSTD	{ int ibcs2_setgroups(int gidsetsize, \
 				    ibcs2_gid_t *gidset); }
 45	AUE_NULL	MSTD	{ int ibcs2_sysconf(int name); }
 46	AUE_PATHCONF	MSTD	{ int ibcs2_pathconf(char *path, int name); }
diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c
index 469659a..2943939 100644
--- a/sys/kern/kern_prot.c
+++ b/sys/kern/kern_prot.c
@@ -63,6 +63,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/resourcevar.h>
 #include <sys/socket.h>
 #include <sys/socketvar.h>
+#include <sys/syscallsubr.h>
 #include <sys/sysctl.h>
 
 #include <security/audit/audit.h>
@@ -297,22 +298,36 @@ struct getgroups_args {
 int
 getgroups(struct thread *td, register struct getgroups_args *uap)
 {
-	struct ucred *cred;
+	gid_t groups[NGROUPS];
 	u_int ngrp;
 	int error;
 
+	ngrp = MIN(uap->gidsetsize, NGROUPS);
+	error = kern_getgroups(td, &ngrp, groups);
+	if (error)
+		return (error);
+	if (uap->gidsetsize > 0)
+		error = copyout(groups, uap->gidset, ngrp * sizeof(gid_t));
+	if (error == 0)
+		td->td_retval[0] = ngrp;
+	return (error);
+}
+
+int
+kern_getgroups(struct thread *td, u_int *ngrp, gid_t *groups)
+{
+	struct ucred *cred;
+
 	cred = td->td_ucred;
-	if ((ngrp = uap->gidsetsize) == 0) {
-		td->td_retval[0] = cred->cr_ngroups;
+	if (*ngrp == 0) {
+		*ngrp = cred->cr_ngroups;
 		return (0);
 	}
-	if (ngrp < cred->cr_ngroups)
+	if (*ngrp < cred->cr_ngroups)
 		return (EINVAL);
-	ngrp = cred->cr_ngroups;
-	error = copyout(cred->cr_groups, uap->gidset, ngrp * sizeof(gid_t));
-	if (error == 0)
-		td->td_retval[0] = ngrp;
-	return (error);
+	*ngrp = cred->cr_ngroups;
+	bcopy(cred->cr_groups, groups, *ngrp * sizeof(gid_t));
+	return (0);
 }
 
 #ifndef _SYS_SYSPROTO_H_
@@ -815,28 +830,33 @@ struct setgroups_args {
 int
 setgroups(struct thread *td, struct setgroups_args *uap)
 {
+	gid_t groups[NGROUPS];
+	int error;
+
+	if (uap->gidsetsize > NGROUPS)
+		return (EINVAL);
+	error = copyin(uap->gidset, groups, uap->gidsetsize * sizeof(gid_t));
+	if (error)
+		return (error);
+	return (kern_setgroups(td, uap->gidsetsize, groups));
+}
+
+int
+kern_setgroups(struct thread *td, u_int ngrp, gid_t *groups)
+{
 	struct proc *p = td->td_proc;
-	struct ucred *newcred, *tempcred, *oldcred;
-	u_int ngrp;
+	struct ucred *newcred, *oldcred;
 	int error;
 
-	ngrp = uap->gidsetsize;
 	if (ngrp > NGROUPS)
 		return (EINVAL);
-	tempcred = crget();
-	error = copyin(uap->gidset, tempcred->cr_groups, ngrp * sizeof(gid_t));
-	if (error != 0) {
-		crfree(tempcred);
-		return (error);
-	}
-	AUDIT_ARG(groupset, tempcred->cr_groups, ngrp);
+	AUDIT_ARG(groupset, groups, ngrp);
 	newcred = crget();
 	PROC_LOCK(p);
 	oldcred = p->p_ucred;
 
 #ifdef MAC
-	error = mac_check_proc_setgroups(p, oldcred, ngrp,
-	    tempcred->cr_groups);
+	error = mac_check_proc_setgroups(p, oldcred, ngrp, groups);
 	if (error)
 		goto fail;
 #endif
@@ -859,21 +879,18 @@ setgroups(struct thread *td, struct setgroups_args *uap)
 		 */
 		newcred->cr_ngroups = 1;
 	} else {
-		bcopy(tempcred->cr_groups, newcred->cr_groups,
-		    ngrp * sizeof(gid_t));
+		bcopy(groups, newcred->cr_groups, ngrp * sizeof(gid_t));
 		newcred->cr_ngroups = ngrp;
 	}
 	setsugid(p);
 	p->p_ucred = newcred;
 	PROC_UNLOCK(p);
-	crfree(tempcred);
 	crfree(oldcred);
 	return (0);
 
 fail:
 	PROC_UNLOCK(p);
 	crfree(newcred);
-	crfree(tempcred);
 	return (error);
 }
 
diff --git a/sys/sys/syscallsubr.h b/sys/sys/syscallsubr.h
index d4f818b..c7a0cd5 100644
--- a/sys/sys/syscallsubr.h
+++ b/sys/sys/syscallsubr.h
@@ -81,6 +81,7 @@ int	kern_futimes(struct thread *td, int fd, struct timeval *tptr,
 	    enum uio_seg tptrseg);
 int	kern_getfsstat(struct thread *td, struct statfs **buf, size_t bufsize,
 	    enum uio_seg bufseg, int flags);
+int	kern_getgroups(struct thread *td, u_int *ngrp, gid_t *groups);
 int	kern_getitimer(struct thread *, u_int, struct itimerval *);
 int	kern_getrusage(struct thread *td, int who, struct rusage *rup);
 int	kern_getsockopt(struct thread *td, int s, int level, int name,
@@ -132,6 +133,7 @@ int	kern_sendfile(struct thread *td, struct sendfile_args *uap,
 	    struct uio *hdr_uio, struct uio *trl_uio, int compat);
 int	kern_sendit(struct thread *td, int s, struct msghdr *mp, int flags,
 	    struct mbuf *control, enum uio_seg segflg);
+int	kern_setgroups(struct thread *td, u_int ngrp, gid_t *groups);
 int	kern_setitimer(struct thread *, u_int, struct itimerval *,
 	    struct itimerval *);
 int	kern_setrlimit(struct thread *, u_int, struct rlimit *);