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CIFS: fix type confusion in copy offload ioctl

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This might lead to local privilege escalation (code execution as
kernel) for systems where the following conditions are met:

 - CONFIG_CIFS_SMB2 and CONFIG_CIFS_POSIX are enabled
 - a cifs filesystem is mounted where:
  - the mount option "vers" was used and set to a value >=2.0
  - the attacker has write access to at least one file on the filesystem

To attack this, an attacker would have to guess the target_tcon
pointer (but guessing wrong doesn't cause a crash, it just returns an
error code) and win a narrow race.

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Jann Horn <jann@thejh.net>
Signed-off-by: Steve French <smfrench@gmail.com>
This commit is contained in:
Jann Horn 2015-09-11 16:27:27 +02:00 committed by Steve French
parent b0a1ea51bd
commit 4c17a6d56b
1 changed files with 6 additions and 0 deletions
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6
fs/cifs/ioctl.c
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@ -67,6 +67,12 @@ static long cifs_ioctl_clone(unsigned int xid, struct file *dst_file,
goto out_drop_write;
}
if (src_file.file->f_op->unlocked_ioctl != cifs_ioctl) {
rc = -EBADF;
cifs_dbg(VFS, "src file seems to be from a different filesystem type\n");
goto out_fput;
}
if ((!src_file.file->private_data) || (!dst_file->private_data)) {
rc = -EBADF;
cifs_dbg(VFS, "missing cifsFileInfo on copy range src file\n");