cifs: make cifs_ioctl handle NULL filp->private_data correctly

Commit 13cfb7334e made cifs_ioctl use the tlink attached to the
cifsFileInfo for a filp. This ignores the case of an open directory
however, which in CIFS can have a NULL private_data until a readdir
is done on it.

This patch re-adds the NULL pointer checks that were removed in commit
50ae28f01 and moves the setting of tcon and "caps" variables lower.

Long term, a better fix would be to establish a f_op->open routine for
directories that populates that field at open time, but that requires
some other changes to how readdir calls are handled.

Reported-by: Kjell Rune Skaaraas <kjella79@yahoo.no>
Reviewed-and-Tested-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c
index 2fa22f20cfc5..0c98672d0122 100644
--- a/fs/cifs/ioctl.c
+++ b/fs/cifs/ioctl.c
@@ -38,10 +38,10 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
         struct cifs_sb_info *cifs_sb;
 #ifdef CONFIG_CIFS_POSIX
         struct cifsFileInfo *pSMBFile = filep->private_data;
-        struct cifsTconInfo *tcon = tlink_tcon(pSMBFile->tlink);
+        struct cifsTconInfo *tcon;
         __u64   ExtAttrBits = 0;
         __u64   ExtAttrMask = 0;
-        __u64   caps = le64_to_cpu(tcon->fsUnixInfo.Capability);
+        __u64   caps;
 #endif /* CONFIG_CIFS_POSIX */
 
         xid = GetXid();
@@ -62,6 +62,10 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
                         break;
 #ifdef CONFIG_CIFS_POSIX
                 case FS_IOC_GETFLAGS:
+                        if (pSMBFile == NULL)
+                                break;
+                        tcon = tlink_tcon(pSMBFile->tlink);
+                        caps = le64_to_cpu(tcon->fsUnixInfo.Capability);
                         if (CIFS_UNIX_EXTATTR_CAP & caps) {
                                 rc = CIFSGetExtAttr(xid, tcon, pSMBFile->netfid,
                                         &ExtAttrBits, &ExtAttrMask);
@@ -73,6 +77,10 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
                         break;
 
                 case FS_IOC_SETFLAGS:
+                        if (pSMBFile == NULL)
+                                break;
+                        tcon = tlink_tcon(pSMBFile->tlink);
+                        caps = le64_to_cpu(tcon->fsUnixInfo.Capability);
                         if (CIFS_UNIX_EXTATTR_CAP & caps) {
                                 if (get_user(ExtAttrBits, (int __user *)arg)) {
                                         rc = -EFAULT;