From a40cd17e13e0b3a2db6098d58aaab8707ce82bf1 Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Thu, 18 Jan 2007 09:32:08 +0000
Subject: Add support for LINUX_O_DIRECT, LINUX_O_DIRECT and LINUX_O_NOFOLLOW
 flags to open() [1]. Improve locking for accessing session control structures
 [2]. Try to document (most likely harmless) races in the code [3].

Based on submission by:	Intron (intron at intron ac) [1]
Reviewed by:		jhb [2]
Discussed with:		netchild, rwatson, jhb [3]
---
 sys/compat/linux/linux_file.c | 63 +++++++++++++++++++++++++++++++------------
 1 file changed, 46 insertions(+), 17 deletions(-)

(limited to 'sys')

diff --git a/sys/compat/linux/linux_file.c b/sys/compat/linux/linux_file.c
index b696fe1..e09f915 100644
--- a/sys/compat/linux/linux_file.c
+++ b/sys/compat/linux/linux_file.c
@@ -45,6 +45,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/mutex.h>
 #include <sys/proc.h>
 #include <sys/stat.h>
+#include <sys/sx.h>
 #include <sys/syscallsubr.h>
 #include <sys/sysproto.h>
 #include <sys/tty.h>
@@ -88,6 +89,8 @@ int
 linux_open(struct thread *td, struct linux_open_args *args)
 {
     struct proc *p = td->td_proc;
+    struct file *fp;
+    int fd;
     char *path;
     int bsd_flags, error;
 
@@ -126,28 +129,54 @@ linux_open(struct thread *td, struct linux_open_args *args)
 	bsd_flags |= O_EXCL;
     if (args->flags & LINUX_O_NOCTTY)
 	bsd_flags |= O_NOCTTY;
+    if (args->flags & LINUX_O_DIRECT)
+	bsd_flags |= O_DIRECT;
+    if (args->flags & LINUX_O_NOFOLLOW)
+	bsd_flags |= O_NOFOLLOW;
+    /* XXX LINUX_O_NOATIME: unable to be easily implemented. */
 
     error = kern_open(td, path, UIO_SYSSPACE, bsd_flags, args->mode);
-    PROC_LOCK(p);
-    if (!error && !(bsd_flags & O_NOCTTY) &&
-	SESS_LEADER(p) && !(p->p_flag & P_CONTROLT)) {
-	struct file *fp;
+    if (!error) {
+	    fd = td->td_retval[0];
+	    /*
+	     * XXX In between kern_open() and fget(), another process
+	     * having the same filedesc could use that fd without
+	     * checking below.
+	     */
+	    error = fget(td, fd, &fp);
+	    if (!error) {
+		    sx_slock(&proctree_lock);
+		    PROC_LOCK(p);
+		    if (!(bsd_flags & O_NOCTTY) &&
+			SESS_LEADER(p) && !(p->p_flag & P_CONTROLT)) {
+			    PROC_UNLOCK(p);
+			    sx_unlock(&proctree_lock);
+			    if (fp->f_type == DTYPE_VNODE)
+				    (void) fo_ioctl(fp, TIOCSCTTY, (caddr_t) 0,
+					     td->td_ucred, td);
+		    } else {
+			    PROC_UNLOCK(p);
+			    sx_sunlock(&proctree_lock);
+		    }
+		    if (args->flags & LINUX_O_DIRECTORY) {
+			    if (fp->f_type != DTYPE_VNODE ||
+				fp->f_vnode->v_type != VDIR) {
+				    error = ENOTDIR;
+			    }
+		    }
+		    fdrop(fp, td);
+		    /*
+		     * XXX as above, fdrop()/kern_close() pair is racy.
+		     */
+		    if (error)
+			    kern_close(td, fd);
+	    }
+    }
 
-	PROC_UNLOCK(p);
-	error = fget(td, td->td_retval[0], &fp);
-	if (!error) {
-		if (fp->f_type == DTYPE_VNODE)
-			fo_ioctl(fp, TIOCSCTTY, (caddr_t) 0, td->td_ucred,
-			    td);
-	    fdrop(fp, td);
-	}
-    } else {
-	PROC_UNLOCK(p);
 #ifdef DEBUG
-	if (ldebug(open))
-		printf(LMSG("open returns error %d"), error);
+    if (ldebug(open))
+	    printf(LMSG("open returns error %d"), error);
 #endif
-    }
     LFREEPATH(path);
     return error;
 }
-- 
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