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

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.

Link: http://lkml.kernel.org/r/20170201140540.22051-1-lokeshvutla@ti.com
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reported-by: Murali Karicheri <m-karicheri2@ti.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Tero Kristo <t-kristo@ti.com>
Cc: Sekhar Nori <nsekhar@ti.com>
Cc: Nishanth Menon <nm@ti.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 2 insertions, 3 deletions

diff --git a/init/initramfs.c b/init/initramfs.c
index b32ad7d97ac9..981f286c1d16 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -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.
diff --git a/init/main.c b/init/main.c
index 24ea48745061..6eb10ce472b9 100644
--- a/init/main.c
+++ b/init/main.c
@@ -71,7 +71,6 @@
 #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>
@@ -960,8 +959,6 @@ static int __ref kernel_init(void *unused)
         system_state = SYSTEM_RUNNING;
         numa_default_policy();
 
-        flush_delayed_fput();
-
         rcu_end_inkernel_boot();
 
         if (ramdisk_execute_command) {