Patch "initramfs: finish fput() before accessing any binary from initramfs" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

initramfs: finish fput() before accessing any binary from initramfs

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
initramfs-finish-fput-before-accessing-any-binary-from-initramfs.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Lokesh Vutla <[email protected]>
Date: Mon, 27 Feb 2017 14:28:12 -0800
Subject: initramfs: finish fput() before accessing any binary from initramfs

From: Lokesh Vutla <[email protected]>

[ Upstream commit 08865514805d2de8e7002fa8149c5de3e391f412 ]

Commit 4a9d4b024a31 ("switch fput to task_work_add") implements a schedule_work() for completing fput(), but did not guarantee calling __fput() after unpacking initramfs. Because of this, there is a possibility that during boot a driver can see ETXTBSY when it tries to load a binary from initramfs as fput() is still pending on that binary.

This patch makes sure that fput() is completed after unpacking initramfs and removes the call to flush_delayed_fput() in kernel_init() which happens very late after unpacking initramfs.

---
 init/initramfs.c |    2 ++
 init/main.c      |    3 ---
 2 files changed, 2 insertions(+), 3 deletions(-)

@@ -18,6 +18,7 @@
 #include <linux/dirent.h>
 #include <linux/syscalls.h>
 #include <linux/utime.h>
+#include <linux/file.h>
 
 static ssize_t __init xwrite(int fd, const char *p, size_t count)
 {

@@ -647,6 +648,7 @@ static int __init populate_rootfs(void)
 			printk(KERN_EMERG "Initramfs unpacking failed: %s\n", err);
 		free_initrd();
 #endif
+		flush_delayed_fput();
 		/*
 		 * Try loading default modules from initramfs.  This gives
 		 * us a chance to load before device_initcalls.

@@ -70,7 +70,6 @@
 #include <linux/shmem_fs.h>
 #include <linux/slab.h>
 #include <linux/perf_event.h>
-#include <linux/file.h>
 #include <linux/ptrace.h>
 #include <linux/blkdev.h>
 #include <linux/elevator.h>

@@ -947,8 +946,6 @@ static int __ref kernel_init(void *unuse
 	system_state = SYSTEM_RUNNING;
 	numa_default_policy();
 
-	flush_delayed_fput();
-
 	rcu_end_inkernel_boot();
 
 	if (ramdisk_execute_command) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/initramfs-finish-fput-before-accessing-any-binary-from-initramfs.patch