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In do_chtls_setsockopt(), the tls crypto info is first copied from the poiner 'optval' in userspace and saved to 'tmp_crypto_info'. Then the 'version' of the crypto info is checked. If the version is not as expected, i.e., TLS_1_2_VERSION, error code -ENOTSUPP is returned to indicate that the provided crypto info is not supported yet. Then, the 'cipher_type' field of the 'tmp_crypto_info' is also checked to see if it is TLS_CIPHER_AES_GCM_128. If it is, the whole struct of tls12_crypto_info_aes_gcm_128 is copied from the pointer 'optval' and then the function chtls_setkey() is invoked to set the key. Given that the 'optval' pointer resides in userspace, a malicious userspace process can race to change the data pointed by 'optval' between the two copies. For example, a user can provide a crypto info with TLS_1_2_VERSION and TLS_CIPHER_AES_GCM_128. After the first copy, the user can modify the 'version' and the 'cipher_type' fields to any versions and/or cipher types that are not allowed. This way, the user can bypass the checks, inject bad data to the kernel, cause chtls_setkey() to set a wrong key or other issues. This patch reuses the data copied in the first try so as to ensure these checks will not be bypassed. Signed-off-by: Wenwen Wang <wang6495@umn.edu> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.