| From | Luis Henriques <> | Subject | [PATCH 3.16.y-ckt 002/104] CIFS: fix type confusion in copy offload ioctl | Date | Mon, 26 Oct 2015 13:41:44 +0000 |
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3.16.7-ckt19 -stable review patch. If anyone has any objections, please let me know.
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From: Jann Horn <jann@thejh.net>
commit 4c17a6d56bb0cad3066a714e94f7185a24b40f49 upstream.
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.
Signed-off-by: Jann Horn <jann@thejh.net> Signed-off-by: Steve French <smfrench@gmail.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- fs/cifs/ioctl.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c index 8b7898b7670f..64a9bca976d0 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");
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