From 246693acf8309ec9b86116ad739d385afccdcdaa Mon Sep 17 00:00:00 2001
From: Antonio Huete Jimenez <tuxillo@quantumachine.net>
Date: Mon, 25 Oct 2010 17:04:37 +0200
Subject: [PATCH] nullfs - Add 'noexec' flag support.

* Make possible to mount a null-mount with 'noexec' option.

* If the underlying filesystem is mounted as 'noexec' and no options
were given at mount-time, the null mount will automatically
have 'noexec'.

Pointed-out-by: @dillon
---
 sys/kern/imgact_elf.c        | 4 +++-
 sys/kern/kern_exec.c         | 8 +++++---
 sys/sys/imgact.h             | 4 +++-
 sys/vfs/nullfs/null_vfsops.c | 2 ++
 4 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c
index 6146fd2b26..d56f1f96b0 100644
--- a/sys/kern/imgact_elf.c
+++ b/sys/kern/imgact_elf.c
@@ -491,6 +491,7 @@ elf_load_file(struct proc *p, const char *file, u_long *addr, u_long *entry)
 	struct vmspace *vmspace = p->p_vmspace;
 	struct vattr *attr;
 	struct image_params *imgp;
+	struct mount *topmnt;
 	vm_prot_t prot;
 	u_long rbase;
 	u_long base_addr = 0;
@@ -515,6 +516,7 @@ elf_load_file(struct proc *p, const char *file, u_long *addr, u_long *entry)
 		error = nlookup(nd);
 	if (error == 0)
 		error = cache_vget(&nd->nl_nch, nd->nl_cred, LK_EXCLUSIVE, &imgp->vp);
+	topmnt = nd->nl_nch.mount;
 	nlookup_done(nd);
 	if (error)
 		goto fail;
@@ -522,7 +524,7 @@ elf_load_file(struct proc *p, const char *file, u_long *addr, u_long *entry)
 	/*
 	 * Check permissions, modes, uid, etc on the file, and "open" it.
 	 */
-	error = exec_check_permissions(imgp);
+	error = exec_check_permissions(imgp, topmnt);
 	if (error) {
 		vn_unlock(imgp->vp);
 		goto fail;
diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index 0236c05d51..4bbb198269 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -237,9 +237,10 @@ interpret:
 		goto exec_fail;
 
 	/*
-	 * Check file permissions (also 'opens' file)
+	 * Check file permissions (also 'opens' file).
+	 * Include also the top level mount in the check.
 	 */
-	error = exec_check_permissions(imgp);
+	error = exec_check_permissions(imgp, nd->nl_nch.mount);
 	if (error) {
 		vn_unlock(imgp->vp);
 		goto exec_fail_dealloc;
@@ -981,7 +982,7 @@ exec_copyout_strings(struct image_params *imgp)
  *	Return 0 for success or error code on failure.
  */
 int
-exec_check_permissions(struct image_params *imgp)
+exec_check_permissions(struct image_params *imgp, struct mount *topmnt)
 {
 	struct proc *p = imgp->proc;
 	struct vnode *vp = imgp->vp;
@@ -1002,6 +1003,7 @@ exec_check_permissions(struct image_params *imgp)
 	 * 3) Insure that the file is a regular file.
 	 */
 	if ((vp->v_mount->mnt_flag & MNT_NOEXEC) ||
+	    ((topmnt != NULL) && (topmnt->mnt_flag & MNT_NOEXEC)) ||
 	    ((attr->va_mode & 0111) == 0) ||
 	    (attr->va_type != VREG)) {
 		return (EACCES);
diff --git a/sys/sys/imgact.h b/sys/sys/imgact.h
index 2d1eb855a4..e70c9a0f07 100644
--- a/sys/sys/imgact.h
+++ b/sys/sys/imgact.h
@@ -37,6 +37,8 @@
 #ifndef _SYS_IMGACT_H_
 #define	_SYS_IMGACT_H_
 
+#include <sys/mount.h>
+
 #define MAXSHELLCMDLEN	128
 
 struct image_args {
@@ -71,7 +73,7 @@ enum	exec_path_segflg {PATH_SYSSPACE, PATH_USERSPACE};
 
 struct vmspace;
 int	exec_resident_imgact (struct image_params *);
-int	exec_check_permissions (struct image_params *);
+int	exec_check_permissions (struct image_params *, struct mount *);
 int	exec_new_vmspace (struct image_params *, struct vmspace *vmres);
 int	exec_shell_imgact (struct image_params *);
 int	exec_copyin_args(struct image_args *, char *, enum exec_path_segflg,
diff --git a/sys/vfs/nullfs/null_vfsops.c b/sys/vfs/nullfs/null_vfsops.c
index 08100eeed6..57901dfc88 100644
--- a/sys/vfs/nullfs/null_vfsops.c
+++ b/sys/vfs/nullfs/null_vfsops.c
@@ -140,6 +140,8 @@ nullfs_mount(struct mount *mp, char *path, caddr_t data, struct ucred *cred)
 	if (xmp->nullm_vfs != rootvp->v_mount) {
 		if (xmp->nullm_vfs->mnt_flag & MNT_RDONLY)
 			mp->mnt_flag |= MNT_RDONLY;
+		if (xmp->nullm_vfs->mnt_flag & MNT_NOEXEC)
+			mp->mnt_flag |= MNT_NOEXEC;
 		xmp->nullm_vfs = rootvp->v_mount;
 	}
 
-- 
2.41.0