From 4c17a6d56bb0cad3066a714e94f7185a24b40f49 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Fri, 11 Sep 2015 16:27:27 +0200 Subject: [PATCH] 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 Signed-off-by: Jann Horn Signed-off-by: Steve French --- fs/cifs/ioctl.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c index c63f5227b681..28a77bf1d559 100644 --- a/fs/cifs/ioctl.c +++ b/fs/cifs/ioctl.c @@ -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"); -- 2.11.0