re: file->f_op is never NULL...

re: file->f_op is never NULL...

[Dan Carpenter]

Hello Ecrypt FS People,

Al Viro has a patch in linux-next and it upsets Smatch:

The patch 72c2d5319200: "file->f_op is never NULL..." from Sep 22, 
2013, leads to the following
static checker warning: "fs/ecryptfs/file.c:320 ecryptfs_unlocked_ioctl()
	 error: potential NULL dereference 'lower_file'."

fs/ecryptfs/file.c
   312  static long
   313  ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
   314  {
   315          struct file *lower_file = NULL;
   316          long rc = -ENOTTY;
   317  
   318          if (ecryptfs_file_to_private(file))
   319                  lower_file = ecryptfs_file_to_lower(file);
   320          if (lower_file->f_op && lower_file->f_op->unlocked_ioctl)
   321                  rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);

If there is no file->private_data then "lower_file" is NULL.  However,
I think file->private_data is always set to a valid pointer in
ecryptfs_open() so really we should just remove the
"if (ecryptfs_file_to_private(file))" check.  Is that right, or am I
missing something.

   322          return rc;
   323  }
   324  
   325  #ifdef CONFIG_COMPAT
   326  static long
   327  ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
   328  {
   329          struct file *lower_file = NULL;
   330          long rc = -ENOIOCTLCMD;
   331  
   332          if (ecryptfs_file_to_private(file))
   333                  lower_file = ecryptfs_file_to_lower(file);
   334          if (lower_file->f_op && lower_file->f_op->compat_ioctl)
   335                  rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);

Same things.

   336          return rc;
   337  }
   338  #endif

regards,
dan carpenter

[PATCH] eCryptfs: file->private_data is always valid

[Tyler Hicks]

When accessing the lower_file pointer located in private_data of
eCryptfs files, there is no need to check to see if the private_data
pointer has been initialized to a non-NULL value. The file->private_data
and file->private_data->lower_file pointers are always initialized to
non-NULL values in ecryptfs_open().

This change quiets a Smatch warning:

  CHECK   /var/scm/kernel/linux/fs/ecryptfs/file.c
fs/ecryptfs/file.c:321 ecryptfs_unlocked_ioctl() error: potential NULL dereference 'lower_file'.
fs/ecryptfs/file.c:335 ecryptfs_compat_ioctl() error: potential NULL dereference 'lower_file'.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
---

Thanks, Dan! You're right that the "if (ecryptfs_file_to_private(file))" check
is not needed.

I'll include this patch in an upcoming pull request.

Tyler

 fs/ecryptfs/file.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
index 2229a74..b1eaa7a 100644
--- a/fs/ecryptfs/file.c
+++ b/fs/ecryptfs/file.c
@@ -313,11 +313,9 @@ static int ecryptfs_fasync(int fd, struct file *file, int flag)
 static long
 ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
-	struct file *lower_file = NULL;
+	struct file *lower_file = ecryptfs_file_to_lower(file);
 	long rc = -ENOTTY;
 
-	if (ecryptfs_file_to_private(file))
-		lower_file = ecryptfs_file_to_lower(file);
 	if (lower_file->f_op->unlocked_ioctl)
 		rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
 	return rc;
@@ -327,11 +325,9 @@ ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 static long
 ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
-	struct file *lower_file = NULL;
+	struct file *lower_file = ecryptfs_file_to_lower(file);
 	long rc = -ENOIOCTLCMD;
 
-	if (ecryptfs_file_to_private(file))
-		lower_file = ecryptfs_file_to_lower(file);
 	if (lower_file->f_op && lower_file->f_op->compat_ioctl)
 		rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
 	return rc;
-- 
1.8.3.2