cifs: dereferencing first then checking
This patch is based on Dan's original patch. His original description is
below:
Smatch complained about a couple checking for NULL after dereferencing
bugs. I'm not super familiar with the code so I did the conservative
thing and move the dereferences after the checks.
The dereferences in cifs_lock() and cifs_fsync() were added in
ba00ba64cf0 "cifs: make various routines use the cifsFileInfo->tcon
pointer". The dereference in find_writable_file() was added in
6508d904e6f "cifs: have find_readable/writable_file filter by fsuid".
The comments there say it's possible to trigger the NULL dereference
under stress.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 71185d1..777e7f4 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -754,12 +754,6 @@
cifs_sb = CIFS_SB(file->f_path.dentry->d_sb);
tcon = tlink_tcon(((struct cifsFileInfo *)file->private_data)->tlink);
-
- if (file->private_data == NULL) {
- rc = -EBADF;
- FreeXid(xid);
- return rc;
- }
netfid = ((struct cifsFileInfo *)file->private_data)->netfid;
if ((tcon->ses->capabilities & CAP_UNIX) &&
@@ -1154,7 +1148,7 @@
bool fsuid_only)
{
struct cifsFileInfo *open_file;
- struct cifs_sb_info *cifs_sb = CIFS_SB(cifs_inode->vfs_inode.i_sb);
+ struct cifs_sb_info *cifs_sb;
bool any_available = false;
int rc;
@@ -1168,6 +1162,8 @@
return NULL;
}
+ cifs_sb = CIFS_SB(cifs_inode->vfs_inode.i_sb);
+
/* only filter by fsuid on multiuser mounts */
if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER))
fsuid_only = false;