smb: client: use finish_no_open() for non-regular inodes

Overview

In the Linux kernel, the following vulnerability has been resolved:

smb: client: use finish_no_open() for non-regular inodes

An O_CREAT open can find an existing symlink or another non-regular inode. cifs_atomic_open() calls finish_open() on it and attaches a cifsFileInfo. Symlink inodes have no CIFS release operation, so the dentry reference held by cifsFileInfo is leaked. FMODE_OPENED also prevents the VFS from following the symlink.

Track whether cifs_do_create() returned an open server handle. For non-regular inodes, close the handle if present, remove the pending open, and call finish_no_open() so the VFS can continue the lookup. Do not set FMODE_CREATED unless a regular file was opened. For O_NOFOLLOW with __O_REGULAR, return -ELOOP before the VFS's -EFTYPE check.

Defer closing a legacy POSIX handle on a non-regular inode until after inode lookup. This avoids closing it again if lookup fails.

Affected

• Linux >= d2c127197dfc0b2bae62a52e1e0d3e3ff493919e < ed03d547598c92a036f20e89156540995cac889a
• Linux >= d2c127197dfc0b2bae62a52e1e0d3e3ff493919e < 70a7918fda54a06d836acc91eb9a3c7e860fe0a0
• Linux >= d2c127197dfc0b2bae62a52e1e0d3e3ff493919e < 3c07deb26273155c180aedfd9041ab58015d2521
• Linux >= d2c127197dfc0b2bae62a52e1e0d3e3ff493919e < e66cf1625ec4a3fe68346119f371def713fd0a4d
• Linux 3.6

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.