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From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Sat, 9 Sep 2017 06:04:05 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r323347 - head/sys/compat/linuxkpi/common/include/linux
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Author: hselasky
Date: Sat Sep  9 06:04:05 2017
New Revision: 323347
URL: https://svnweb.freebsd.org/changeset/base/323347

Log:
  Add more sanity checks to linux_fget() in the LinuxKPI. This prevents
  returning pointers to file descriptors which were not created by the
  LinuxKPI.
  
  MFC after:		1 week
  Sponsored by:		Mellanox Technologies

Modified:
  head/sys/compat/linuxkpi/common/include/linux/file.h

Modified: head/sys/compat/linuxkpi/common/include/linux/file.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/linux/file.h	Sat Sep  9 05:56:04 2017	(r323346)
+++ head/sys/compat/linuxkpi/common/include/linux/file.h	Sat Sep  9 06:04:05 2017	(r323347)
@@ -53,11 +53,18 @@ linux_fget(unsigned int fd)
 	cap_rights_t rights;
 	struct file *file;
 
+	/* lookup file pointer by file descriptor index */
 	if (fget_unlocked(curthread->td_proc->p_fd, fd,
-	    cap_rights_init(&rights), &file, NULL) != 0) {
+	    cap_rights_init(&rights), &file, NULL) != 0)
 		return (NULL);
+
+	/* check if file handle really belongs to us */
+	if (file->f_data == NULL ||
+	    file->f_ops != &linuxfileops) {
+		fdrop(file, curthread);
+		return (NULL);
 	}
-	return (struct linux_file *)file->f_data;
+	return ((struct linux_file *)file->f_data);
 }
 
 extern void linux_file_free(struct linux_file *filp);