From 28a7f60741b8e92fb0fc05e1febd362b6d0eaef9 Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Sun, 8 Jul 2012 00:51:38 +0000
Subject: [PATCH] Unbreak handling of descriptors opened with O_EXEC by
 fexecve(2).

While here return EBADF for descriptors opened for writing (previously it was ETXTBSY).

Add fgetvp_exec function which performs appropriate checks.

PR:		kern/169651
In collaboration with:	kib
Approved by:	trasz (mentor)
MFC after:	1 week
---
 sys/kern/kern_descrip.c | 13 ++++++++++---
 sys/kern/kern_exec.c    |  4 +++-
 sys/sys/file.h          |  2 ++
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index d16746ad703e..a4b7580b3666 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -2340,11 +2340,11 @@ _fget(struct thread *td, int fd, struct file **fpp, int flags,
 
 	/*
 	 * FREAD and FWRITE failure return EBADF as per POSIX.
-	 *
-	 * Only one flag, or 0, may be specified.
 	 */
 	if ((flags == FREAD && (fp->f_flag & FREAD) == 0) ||
-	    (flags == FWRITE && (fp->f_flag & FWRITE) == 0)) {
+	    (flags == FWRITE && (fp->f_flag & FWRITE) == 0) ||
+	    (flags == (FREAD | FEXEC) &&
+	    (((fp->f_flag & flags) == 0) || ((fp->f_flag & FWRITE) != 0)))) {
 		fdrop(fp, td);
 		return (EBADF);
 	}
@@ -2444,6 +2444,13 @@ fgetvp_read(struct thread *td, int fd, cap_rights_t rights, struct vnode **vpp)
 	return (_fgetvp(td, fd, FREAD, rights, NULL, vpp));
 }
 
+int
+fgetvp_exec(struct thread *td, int fd, cap_rights_t rights, struct vnode **vpp)
+{
+
+	return (_fgetvp(td, fd, FREAD | FEXEC, rights, NULL, vpp));
+}
+
 #ifdef notyet
 int
 fgetvp_write(struct thread *td, int fd, cap_rights_t rights,
diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index 414a826e74b8..90f7311b8209 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -443,8 +443,10 @@ do_execve(td, args, mac_p)
 		/*
 		 * Some might argue that CAP_READ and/or CAP_MMAP should also
 		 * be required here; such arguments will be entertained.
+		 *
+		 * Descriptors opened only with O_EXEC or O_RDONLY are allowed.
 		 */
-		error = fgetvp_read(td, args->fd, CAP_FEXECVE, &binvp);
+		error = fgetvp_exec(td, args->fd, CAP_FEXECVE, &binvp);
 		if (error)
 			goto exec_fail;
 		vfslocked = VFS_LOCK_GIANT(binvp->v_mount);
diff --git a/sys/sys/file.h b/sys/sys/file.h
index c4c6dbfc7a39..dc49895fa089 100644
--- a/sys/sys/file.h
+++ b/sys/sys/file.h
@@ -238,6 +238,8 @@ fo_chown_t	invfo_chown;
 
 void finit(struct file *, u_int, short, void *, struct fileops *);
 int fgetvp(struct thread *td, int fd, cap_rights_t rights, struct vnode **vpp);
+int fgetvp_exec(struct thread *td, int fd, cap_rights_t rights,
+    struct vnode **vpp);
 int fgetvp_rights(struct thread *td, int fd, cap_rights_t need,
     cap_rights_t *have, struct vnode **vpp);
 int fgetvp_read(struct thread *td, int fd, cap_rights_t rights,