svn commit: r319444 - in head/sys/compat/linuxkpi/common: include/linux src

[Hans Petter Selasky]

Author: hselasky
Date: Thu Jun  1 16:49:48 2017
New Revision: 319444
URL: https://svnweb.freebsd.org/changeset/base/319444

Log:
  Make sure the selrecord() function is only called from within system
  polling contexts in the LinuxKPI.
  
  After the kqueue() support was added to the LinuxKPI in r319409 the
  Linux poll file operation will be used outside the system file polling
  callback function, which can cause a NULL-pointer panic inside
  selrecord() because curthread->td_sel is set to NULL. This patch moves
  the selrecord() call away from poll_wait() and to the system file poll
  callback function in the LinuxKPI, which essentially wraps the Linux
  one. This is similar to what the cuse(3) module is currently doing.
  Refer to sys/fs/cuse/*.[ch] for more details.
  
  MFC after:		1 week
  Sponsored by:		Mellanox Technologies

Modified:
  head/sys/compat/linuxkpi/common/include/linux/poll.h
  head/sys/compat/linuxkpi/common/src/linux_compat.c

Modified: head/sys/compat/linuxkpi/common/include/linux/poll.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/linux/poll.h	Thu Jun  1 16:44:39 2017	(r319443)
+++ head/sys/compat/linuxkpi/common/include/linux/poll.h	Thu Jun  1 16:49:48 2017	(r319444)
@@ -43,7 +43,7 @@ typedef struct poll_table_struct {
 static inline void
 poll_wait(struct linux_file *filp, wait_queue_head_t *wait_address, poll_table *p)
 {
-	selrecord(curthread, &filp->f_selinfo);
+	/* NOP */
 }
 
 extern void linux_poll_wakeup(struct linux_file *);

Modified: head/sys/compat/linuxkpi/common/src/linux_compat.c
==============================================================================
--- head/sys/compat/linuxkpi/common/src/linux_compat.c	Thu Jun  1 16:44:39 2017	(r319443)
+++ head/sys/compat/linuxkpi/common/src/linux_compat.c	Thu Jun  1 16:49:48 2017	(r319444)
@@ -956,9 +956,10 @@ linux_dev_poll(struct cdev *dev, int events, struct th
 	file = td->td_fpop;
 	filp->f_flags = file->f_flag;
 	linux_set_current(td);
-	if (filp->f_op->poll)
+	if (filp->f_op->poll != NULL) {
+		selrecord(td, &filp->f_selinfo);
 		revents = filp->f_op->poll(filp, NULL) & events;
-	else
+	} else
 		revents = 0;
 
 	return (revents);
@@ -1263,9 +1264,10 @@ linux_file_poll(struct file *file, int events, struct 
 	filp = (struct linux_file *)file->f_data;
 	filp->f_flags = file->f_flag;
 	linux_set_current(td);
-	if (filp->f_op->poll)
+	if (filp->f_op->poll != NULL) {
+		selrecord(td, &filp->f_selinfo);
 		revents = filp->f_op->poll(filp, NULL) & events;
-	else
+	} else
 		revents = 0;
 
 	return (revents);