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cifs: dereferencing first then checking

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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
ba00ba64cf "cifs: make various routines use the cifsFileInfo->tcon
pointer".  The dereference in find_writable_file() was added in
6508d904e6 "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>
This commit is contained in:
Jeff Layton 2010-11-02 16:22:50 -04:00 committed by Steve French
parent 6ef933a38a
commit d38922949d
1 changed files with 3 additions and 7 deletions
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10
fs/cifs/file.c
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@ -754,12 +754,6 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
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 @@ struct cifsFileInfo *find_writable_file(struct cifsInodeInfo *cifs_inode,
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 @@ struct cifsFileInfo *find_writable_file(struct cifsInodeInfo *cifs_inode,
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;