CIFS: fix type confusion in copy offload ioctl
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>
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@ -67,6 +67,12 @@ static long cifs_ioctl_clone(unsigned int xid, struct file *dst_file,
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goto out_drop_write;
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}
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if (src_file.file->f_op->unlocked_ioctl != cifs_ioctl) {
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rc = -EBADF;
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cifs_dbg(VFS, "src file seems to be from a different filesystem type\n");
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goto out_fput;
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}
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if ((!src_file.file->private_data) || (!dst_file->private_data)) {
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rc = -EBADF;
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cifs_dbg(VFS, "missing cifsFileInfo on copy range src file\n");
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